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Deep and High-temperature HydrothermalCirculation in the Oman Ophiolite-------Petrological and Isotopic Evidence

D BOSCH1 M JAMAIS1 F BOUDIER1 A NICOLAS1J-M DAUTRIA1 AND P AGRINIER2

1LABORATOIRE DE TECTONOPHYSIQUE UMR 5568 CNRSUM2 UNIVERSITEE MONTPELLIER II PL EUGENE

BATAILLON 34095 MONTPELLIER CEDEX 5 FRANCE

2LABORATOIRE DE GEEOCHIMIE DES ISOTOPES STABLES IPG-PARIS VII 4 PLACE JUSSIEU F-75252 PARIS CEDEX 05

FRANCE

RECEIVED NOVEMBER 28 2001 ACCEPTED DECEMBER 5 2003

A systematic search for evidence of high-temperature hydrous

alteration within the gabbros of the Samail ophiolite (Oman)

shows that most of the gabbros have been affected by successive

stages of alteration starting above 975C and ending below

500C Sr and O isotopic analyses provide constraints on the

nature and origin of the fluids associated with these alteration

events Massive gabbros dykes and veins and their associated

minerals depart from mid-ocean ridge basalt (MORB)-source

magma signatures ( 87Sr86Sr 407032 and depleted d18O56) These isotopic characteristics identify seawater as the

most likely hydrothermal contaminant Samples affected by low-

temperature alteration during greenschist-facies metamorphism are

characterized by high waterrock ratios (410) A second group of

samples including massive gabbros and high-temperature dykes and

veins is characterized by lower waterrock ratios in the range of

3---5 These samples display a high-temperature hydrothermal

alteration related to seawater ingression The main fluid channels

may be sub-millimetre-sized microcracks with a dominantly vertical

attitude which constitute the recharge hydrothermal system whereas

the dykes and veins represent the discharge part This model requires

that these dykes have been generated by hydration of the crystallizing

gabbros via seawater penetration near the internal wall of the

magma chamber

KEY WORDS hydrothermal systems Oman ophiolite Sr and O isotopes

gabbros and massive dykes

INTRODUCTION

Hydrothermal circulation near fast-spreading oceanicridges is typically a greenschist-facies low-temperature(LT) system (T 5 450C) which operates at the ridgeaxis down to the base of the sheeted dyke complex andpenetrates the entire crust once it has drifted away fromthe ridge axis (Nehlig amp Juteau 1988 Wilcock ampDelaney 1996 Juteau et al 2000) The existence of asimultaneous deeper and higher-temperature hydro-thermal system also active at the ridge was firstsuspected when Gregory amp Taylor (1981) on the basisof oxygen isotope data and Lanphere (1981) andMcCulloch et al (1981) on the basis of strontium isotopedata proposed seawater contamination at high temperat-ures (HT) of the lower gabbros of the Oman ophioliteMore recently petrological studies of the upper gab-

bros drilled in the fast-spreading crust exposed in theHess Deep during Ocean Drilling Program (ODP) Leg147 (Mevel et al 1996) have revealed that solid-statereactions in hydrothermal veins occurred at 700---750C pointing to the existence of hydrothermal circula-tion at amphibolite-facies conditions within this section ofoceanic crust Manning et al (2000) conducted a similarstudy of the gabbros from one section in the Nakhl massifof the Oman ophiolite (Fig 1) They calculated temperat-ures ranging from 700C in the uppermost gabbros to825C in the deepest gabbros at the Moho Kawahata

JOURNAL OF PETROLOGY VOLUME 45 NUMBER 6 PAGES 1181ndash1208 2004 DOI 101093petrologyegh010

Corresponding author E-mail boschdstuuniv-montp2fr

Journal of Petrology 45(6) Oxford University Press 2004 all rights

reserved

et al (2001) on the basis of a Sr isotope study of the crustalunit in the Fizh massif of northern Oman found a rise inthe temperature of hydrothermal alteration from lowgreenschist facies in the basalts to amphibolite-facies con-ditions in the gabbrosBoudier et al (2000) have also suggested that seawater

could contaminate the lower gabbros during their crystal-lization as recorded by the crystallization of gabbro-norites in place of olivine gabbros This contaminationat very high temperatures (VHT) possibly as high as1200C is restricted to those parts of the Oman palaeo-ridge that display evidence of ridge-related tectonic activ-ity and the seawater contamination was attributed to thisparticular tectonic setting

Improved seismological modelling of fast-spreadingridges at the East Pacific Rise axis at 9300N has sug-gested that there may be significant narrowing of thelow-velocity zone (LVZ) below the melt lens (Dunn et al2000) with respect to earlier models This narrowingwas explicitly ascribed by Dunn et al to the existence ofdeep high-T hydrothermal circulation at modern oceanicridges This raises the question of the definition of whatshould be considered as the magma chamber below amid-ocean ridge On the basis of extensive studies of theSamail ophiolite Nicolas et al (1988) have shown that themagma chamber was tent-shaped in three dimensionsextending to the base of the crust consistent with theshape of the LVZ found below modern ridges Hence the

Fig 1 (a) Simplified map of the Oman---UAE ophiolite including the inferred location of the palaeo-ridge axes and main shear zones [modifiedfrom Nicolas et al (2000)] (b) Simplified map of the Samail ophiolite Thin numbered lines represent the log-sections of Fig 4 along wadis wherealteration facies have been studied Bold lines are the wadi sections selected for detailed petrological and geochemical work in this study

JOURNAL OF PETROLOGY VOLUME 45 NUMBER 6 JUNE 2004

1182

magma chamber is not restricted to the perched axialmelt lens that is present just below the sheeted dykecomplex of fast-spreading ridges (Detrick et al 1987)because in spite of its very low melt fraction the LVZ isstill deforming as a mush (Nicolas amp Ildefonse 1996)Building on the previous work of MacLeod amp Rothery

(1992) and Nehlig et al (1994) Nicolas et al (2001) haverecently published a structural map of the greenschist-facies hydrothermal veins throughout the Samail ophio-lite This confirms that the LT veins penetrate the entirecrust and are dominantly aligned parallel to the sheeteddyke complex Subsidiary preferred orientations arerelated to changes in the stress field during the dyingactivity of the palaeo-ridge system (Nicolas et al 2000)In a companion paper to the present study Nicolas et al

(2003) described a complete transition from these LThydrothermal veins to gabbroic dykes which suggests thepossibility of seawater-related hydrous melting of the gab-bros or entry of seawater into the partially molten magmachamber Previously these gabbroic dykes which arefairly common in the Oman gabbros were interpreted aslate crystallization products from the LVZ magma cham-ber (Pallister amp Hopson 1981) or as melt conduits relatedto its magmatic activity (Kelemen et al 1997 Kelemen amp

Aharonov 1998) If the magma that produced these gab-broic dykes originated within the magma chamber thewater should also have an internal origin the source beingeither the mantle or the melt lens In the latter case con-tamination by seawater is possible when hydrated diabasefrom the overlying sheeted dyke complex is stoped in themelt lens remelted and dewatered during subsequentsubsidence through the magma chamberAlternatively the gabbroic dykes could result from

fractures external to the magma chamber driving sea-water to great depth In the physical model proposed byNicolas et al (2003) the gabbroic dykes are generated byhydrous melting and represent the discharge system ofthe high-temperature hydrothermal circulation reachingthe inner margin of the magma chamber (Fig 2) Therecharge system is formed by a microcrack network con-trolled by the anisotropy of thermal expansion and oper-ating at falling temperatures below 1200C within adistance of 10 km from the spreading axisThe available geochemical evidence bearing on the

hydrothermal alteration of the gabbros (Gregory ampTaylor 1981 Lanphere 1981 McCulloch et al 1981Kawahata et al 2001) favours a seawater origin withseawaterrock ratios ranging from one (Gregory amp

water in Sea Floor

Magma chamber

water out

gabbroicdike

hydrous contamination

diabase dykeswith chilledmargins

diabasedikewithoutchilledmargins

750degC

500degC

1200degC

LT hydrothermal vein

hydrothermal cracks

hydrothermal cracks

VHT

plastic mantle flow

maficdike

Moho

microgabbrodike

HT

Fig 2 Scheme of hydrothermal circulation near the limit of the magma chamber below the fast-spreading ridge The downgoing seawater flow fillsthe porous network created by microcracks down to the magma chamber where it reacts with the crystallizing melt it surges back towards theseafloor along a system of hydrous gabbroic dykes Modified from Nicolas et al (2003)

BOSCH et al HYDROTHERMAL CIRCULATION IN OMAN OPHIOLITE

1183

Taylor 1981) to as high as nine (Kawahata et al 2001)Oxygen isotope data (C Lecuyer personal communica-tion 1990) on mafic dykes emplaced in the peridotites at1 km below the Moho suggest a dual source of hydrationfor the gabbros in which clinopyroxenes have a mantlesignature but associated plagioclase and brown horn-blende show evidence of seawater contamination Thisdual source was not ruled out by Benoit et al (1996) intheir Sr isotope study of similar dykes injected into themantle section Rare earth element partition coefficientsin clinopyroxene plagioclase and amphibole were usedby the above workers to constrain the temperature ofseawater contamination at the gabbro solidusThus there is growing evidence that supports a deep

penetration of high-T hydrothermal fluids into theoceanic crust at the ridge axis We have conducted asystematic study of the gabbros in the Samail ophioliteand along selected wadi sections (Fig 1) in the hydratedgabbroic dykes that cross-cut them looking for traces ofHT alterationThis study combines microtextural and petrological

observations thermometric determinations and O---Srisotope data on the same gabbroic dykes and surroundinggabbros selected with a view to determine the origin ofhydrous fluid contamination These results have import-ant consequences for thermal modelling of the oceaniccrust near fast-spreading ridges and on the budget ofchemical exchanges between the oceanic crust andseawater

HYDROUS ALTERATION OF

PRIMARY MINERALS IN THE

GABBRO SECTION

The penetrative alteration of the gabbro section has beenstudied on the basis of an extensive thin-section collec-tion which covers the entire ophiolite The studied gab-bros range from the root zone of the sheeted dykecomplex down to the Moho and the Moho transitionzone (MTZ) From the 500 specimens that have beenscreened those sites involved in tectonic complexitiessuch as the end of segments or tips of propagating rifts(Fig 1) have been rejected thus reducing the number ofstudied areas and the number of fully characterized speci-mens to 414 representative of standard gabbros at a fast-spreading palaeo-ridge In this study we mainly focus onhydrous alteration of olivine and clinopyroxene as theseare the minerals most affected by high-T alteration(above 800C) although plagioclase is stable down tothis temperature

Alteration facies

The following types of hydrous parageneses in thegabbros have been distinguished from highest to lowesttemperatures

(1) Orthopyroxene partial coronas between olivine andplagioclase which may be associated with the firstappearance of brown pargasite blebs inside clinopyrox-ene and development of pargasite between olivine andplagioclase or clinopyroxene and plagioclase (Fig 3a) Thebrown pargasite locally grades into a greenish magnesio-hornblende Although the orthopyroxene coronas couldbe assigned to a late magmatic stage we interpret themas reactive (a) being restricted to the contact betweenolivine and plagioclase thus postdating the crystallizationof plagioclase (b) being locally relayed by kelyphiticcoronas that spread into plagioclase microcracks(Fig 3b) as microphases among which diopside andlow-titanium pargasite have been identified We inferthat these reactions are related to an oxygen fugacityincrease as a result of seawater input Based on experi-ments at 2MPa pressure Koepke et al (2003) have con-strained the equilibrium olivine---orthopyroxene at lowwater content at 1030C and 950C at higher watercontent the limit at which amphibole is stabilized Byreference to this experimental work we estimate that thetemperature of equilibration for these reactions referredto here as VHT (very high temperature) hydrous altera-tion was between 900 and 1000C(2) Chlorite and pale amphibole coronas between oliv-

ine and plagioclase (Fig 3d) The coronas are composedof successive rims of clino-amphibole (tremolite) thornmagnetite Mg-chlorite (clinochlore) and a fringe of ortho-amphibole against plagioclase As described above theseminerals are associated with blebs of brown to greenishamphibole inside the pyroxenes (Fig 3c) Depending onthe degree of alteration olivine is surrounded by a thinfilm of amphibole and chlorite or is totally replaced by anassemblage of tremolite thorn magnetite thorn plagioclase An91(thorn talc) surrounded by chlorite (Fig 3e) The evolution ofthe first assemblage to Mg-chlorite indicates temperat-ures above 700C the upper breakdown of Mg-chloriteat 2 kbar (Chernosky et al 1988) The development ofpargasitic amphibole replacing clinopyroxene impliestemperatures between 550 and 900C (Liou et al 1974Spear 1981) We refer to these as HT (high temperature)(3) Iddingsite partly or totally replacing olivine inde-

pendently of orthopyroxene or chlorite---amphibole cor-onas and any significant HT alteration in clinopyroxene(Fig 3f ) Observations in thin sections show that thechlorite---amphibole coronas develop before the idding-site alteration(4) Lizardite alteration of olivine forming the familiar

mesh structure This is always accompanied by saussuritein plagioclase This alteration takes place below 500Cand is here referred to as LT (low temperature) hydrousalteration It is only at this stage that plagioclase showssigns of alterationThese various hydrous alteration facies are commonly

observed superimposed in a set of thin sections from a


1184

single outcrop and even in a single thin section As a rulethe orthopyroxene reactions are more penetrative beinghomogeneously distributed from the scale of a thinsection to that of several thin sections made from a

given outcrop The distribution of chlorite---amphibolecoronas is similar although they can be restricted to themargins of microcracks filled by the same minerals whichhave been interpreted as the channels that carried the

(a) (b)

(c) (d)

(e) (f)

olopx

kel

pl

ol

hbol

amcpx

cpx

hb

chl

am+pl+mt

idg

am

hb

pl

hb

ol

cpx

opx

mt

pl

Fig 3 Hydrothermal alteration in the gabbros (scale bar represents 1mm) (a) VHT alteration marked by orthopyroxene (opx) coronas at thecontact of olivine (ol) and plagioclase (pl) and pargasitic hornblende (hb) at the contact of olivine and clinopyroxene (cpx) (sample 94 MA2)(b) Kelyphite (kel) coronas around olivine and cloudy plagioclase as a result of silicate and fluid inclusions Silicate inclusions tend to be localizedat grain boundaries and along microcracks (sample 94 MA2) (c) VHT alteration marked by brown amphibole (hb) alteration of clinopyroxene in anupper gabbro (d) HT alteration marked by chlorite (chl) (external rim) and pale amphibole (am) and magnetite (mt) (internal rim) coronas aroundolivine (e) Total replacement of olivine by an assemblage of tremolite (am)thornmagnetite (mt)thorn plagioclase (pl) (f ) Total replacement of olivine by aniddingsitic mixture (idg) inside a VHT recrystallized corona of a mosaic of orthopyroxene


1185

fluids responsible for the hydrothermal alteration (Nicolaset al 2003) The iddingsite replacement is typicallyheterogeneous at the thin-section scale being preferen-tially associated with microcracks Serpentinization alsodevelops from microcracks but it can pervasively invadethe entire thin section The microcracks are commonapproximately 25 of the studied thin sections displayone or more Ignoring the cracks related to LT alterationand considering only the cracks related to the HT hydro-thermal alteration this fraction is still around 20

Distribution of high-T alteration facies

Figure 4 shows the distribution of alteration facies as afunction of depth in the crust along wadi sections throughthe Oman---UAE ophiolite offering continuous exposures(see details in Fig 1) Figure 4 excludes the LT faciesbecause (1) being based on the presence of olivine ser-pentinization only throughout our compilation its dis-tribution is biased by the decreasing amount of olivineupsection and (2) this study concerns high-temperaturealteration processes Despite the fact that the scale ofsampling may exceed the scale of heterogeneity evidencefor both VHT alteration and lsquono alterationrsquo increaseswith depth Conversely HT alteration is predominantin the middle and upper parts of the gabbro sectionThis observation is valid throughout the wadi sectionsstudied with the exception of the Wadi Tayin massifwhich shows no clear gradation with depthFigure 5 is another representation of alteration-facies

distribution with depth based on the detailed study of414 thin sections The samples are classified according totheir level in the gabbro section sheeted dyke root zonegabbros upper gabbros middle gabbros lower gabbrosand Moho gabbros (the Moho gabbros have beengrouped together with the gabbro lenses interlayered inthe dunites of the MTZ) Values represent the percent of

2 Km

3

4

5

6

7

Aswad Fizh Hilti Haylayn Samail W TayinNakhl

High T

Very High T

0 High T

Upper Crust

LID

Lower Crust

MohoMTZ

DEPTH1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

Fig 4 Depth of penetration of hydrothermal circulation in gabbros along the wadi sections numbered in Fig 1 referring to alteration faciesdescribed in Fig 3 Depths are recorded below the palaeo-seafloor LID corresponds to the upper crust including sheeted dykes and volcanics

0

10

20

30

40

50

60

70

80

90

100

SD root

zone

upper

gabbros

middle

gabbros

lower

gabbros

MTZ

BHb-GHb CPX

Chl-Amph core OL

Chl-Amph rim OL

0

5

10

15

20

25

30

SD root

zone

upper

gabbros

middle

gabbros

lower

gabbros

MTZ

Opx OL

BHb OL

No VHTHT

Unaltered OL core

HT

VHT

(a)

(b)

Plst def

gabbros

Fig 5 Compilation of hydrothermal alteration features as a function ofdepth in the gabbro section Percentages represent the occurrence of agiven type of alteration versus the number of thin sections examined foreach selected level root of the sheeted dykes (SD) upper gabbros middlegabbros lower gabbros MTZ (Moho Transition Zone) gabbros on atotal amount of 414 thin sections (Opx orthopyroxene Amph amphi-bole OL olivine BHb brown hornblende GHb green hornblendeChl chlorite Plst def plastic deformation) (a) Distribution of the HTalteration (in ) (b) Distribution of the VHT alteration (in )


1186

a given alteration facies as defined previously out of thetotal number of thin sections examined for a given levelMore refined conclusions can be drawn from this figureAs seen in Fig 5a the HT alteration decreases down-

wards whereas it affects most of the upper gabbroicsection (sheeted dyke root zone and upper gabbros)The fraction of unaltered olivine cores can be used asan index to estimate the extent of alteration This indexshows that the HT alteration is more penetrative andintense in the upper gabbros a conclusion alreadyreached by several workers (eg Gregory amp Taylor1981 Stakes amp Taylor 1992 Kawahata et al 2001)This was also noted by Manning et al (1996a 1996b)Figure 5b shows that the VHT alteration marked by

orthopyroxene or brown hornblende coronas aroundolivine increases with depth The correlation betweenthe VHT alteration and plastic deformation also suggeststhat the VHT alteration may coincide with the develop-ment of plastic flow at the expense of the magmatic flow

at temperatures just below the solidus In Fig 5b thefraction of gabbros where there is no VHT---HThydrothermal alteration increases downsection indicat-ing that the VHT---HT alteration is more localizeddownsection

Gabbroic dykes and veins

The occurrence of gabbroic dykes in the layered gabbrosof the Samail ophiolite is ubiquitous We describe gab-broic dykes and sills either plagioclase---clinopyroxeneand brown amphibole-bearing dykes or microgabbrosand amphibolitized dolerite dykes and sills correspond-ing to temperatures up to 975C (see below) Identifica-tion of gabbroic dykes in the field is not alwaysstraightforward because they may be obliterated bysuperimposition of greenschist-facies alteration (Fig 6a)Selective greenschist-facies alteration has frequently beenobserved either in the centre of a mafic dyke or alongboth margins (Fig 6b) as well as a continuous transition

(b) (c)(a)

(d) (e)

thulite

pistacite

white microvein

white vein

green vein

green vein

gabbroic dike

epidote vein

gabbroic dike

Fig 6 Field relationships of dykes and veins (scale bar represents 10 cm) (a) Thulite---pistacite vein cross-cutting a foliated gabbro matrix Reactionmargins marked by the development of secondary clinopyroxene (01 OA36b) (b) Comb-like structure in gabbroic dyke A pink epidote vein followsthe margin of the dyke (01 OA15f) (c) Along-strike transition from a gabbroic dykelet to a hydrothermal green amphibole vein (d) White prehnitevein (e) Green amphibole vein cross-cut by white prehnite vein


1187

along a single crack from a mafic dyke to a hydrothermalvein (Fig 6c) We define hydrothermal veins as cracksfilled with greenschist-facies minerals that induce meta-morphic reactions in the adjacent country rocks andgabbroic dykes as planar intrusive bodies produced bythe crystallization of magma Following Nehlig amp Juteau(1988) we distinguish low-T greenschist-facies lsquowhiteveinsrsquo made of prehnite epidote chlorite and actinolite(Fig 6d) and lsquogreen veinsrsquo in which a darker greenamphibole predominates (Fig 6e) corresponding respec-tively to lower (195---410C) and higher (400---530C)temperatures (Nehlig amp Juteau 1988)The gabbroic dykes are typically a few centimetres

across composed of plagioclase clinopyroxene andbrown

hornblende They are coarse-grained to pegmatitic andcommonly display a comb-like structure (Fig 6b)Although the spacing between the dykes in the field ishighly variable the average is around 10m Gabbroicsills grade from clear intrusions to irregular and diffusepegmatitic gabbro patches up to a few metres in theirlarger dimension (Fig 7a)The distribution in the field of brownish pargasite

which appears black and glassy in outcrop is critical intracing the origin of the gabbroic dykes It is first observedat any level in the host lower and middle gabbros as largepoikilitic patches (Fig 7b) locally associated with simil-arly poikilitic patches of clino- and orthopyroxene(Fig 7a) These patches contain small aligned tablets of

(a) (b) (c)

g(e)(d)

alignment ofalignment of amphiboleamphibole oikocrystsoikocrysts

hwhite vein

hblpl

pcpx

brownbrownamphiboleamphiboleoikocrystoikocryst

eediabasedikdike

hb-plhb-plreactionreaction

imarginspbrown amphibole rich

gabbroic dikegabbroic dike

pbrown amphibole veins

Fig 7 Field relationships of dykes (scale bar is 10 cm long) (a) Irregular coarse to pegmatitic patches in a foliated gabbro matrix (01 OA42d)(b) Alignment of black amphibole oikocrysts in a foliated gabbro matrix (c) Local concentration of brown amphibole in a gabbroic dykelet Theplagioclase laths marking the foliation in the enclosing gabbro rotate into parallelism with the gabbroic dykelet (d) Two diabase dykes assimilatingthe enclosing layered gabbro with plagioclase---amphibole reaction margins (e) Pargasite-rich gabbroic dyke with wall reactions (01 OA19) (Notesmall pargasite---plagioclase veins) pl plagioclase cpx clinopyroxene hb hornblende


1188

plagioclase oriented parallel to the larger plagioclaselaths defining the magmatic foliation of the gabbro(Fig 7c) Clinopyroxene oikocrysts surrounding idio-morphic plagioclase crystals are common in the upper-level gabbros they mark the end of the magmatic flowand crystallization growing before the pargasite andorthopyroxene oikocrysts as shown by their partialreplacement by pargasite Their crystallization marksthe transition at suprasolidus conditions from a dry to awet environment In the uppermost gabbros those dykesthat are typically altered in the HT hydrothermal faciesgrade upwards into the so-called lsquoisotropicrsquo or lsquovari-texturedrsquo gabbrosThe microgabbro and amphibolitized dolerite dykes

differ from the typical diabase dykes commonly cuttingthe gabbro section that have chilled margins and thusprobably intruded enclosing rocks already at temperat-ures below 450C In microgabbro and amphibolitizeddolerite dykes the absence of chilled margins and thedevelopment of dioritic reaction margins in the adjacentgabbro (Fig 7d and e) suggest that they were emplaced ingabbros that were still at temperatures above 750C(Nicolas et al 2000)

ANALYTICAL TECHNIQUES

Major and trace elements

Major element compositions were determined by elec-tron microprobe at the University of Montpellier II usinga Camebax SX100 Instrument calibration was per-formed on natural standards and operating conditionswere 20 kV accelerating potential 10 nA beam currentand 30 s counting timeRb and Sr concentrations in whole rock and separated

mineral fractions were measured by conventionalnebulization inductively coupled plasma mass spectro-metry (ICP-MS) using a VG Plasmaquad 2 (ISTEEMMontpellier) Digestion procedures followed thoseoutlined by Ionov et al (1992)

O---Sr isotopes

The samples selected for the detailed study wereextracted from gabbroic dykes or veins inside gabbrosand cut with a diamond saw into 2---3 cm fragmentsbefore being crushed into 05---1 cm fragments Forwhole-rock analysis small pieces were further crushedinto powder in an agate bowl For pure mineral analysisthe fragments were crushed with a manual agate mortarTo avoid or minimize the mixing of selected separateminerals with other phases that can bias the results astrict protocol of mineral selection was applied A smallsize fraction of 125---160 mm was used and minerals werefirst separated using a Frantz isodynamic magneticseparator Concentrates recovered (cpx plagioclase

amphibole epidote) were subsequently purified by care-ful hand-picking in alcohol under a binocular micro-scope At this stage mineral separates were very pureand only flawless minerals free of cracks and visibleinclusions were kept for isotopic analyses To ensurefurther mineral integrity these pure mineral separateswere ultrasonically washed in dilute 15N HCl and rinsedseveral times with ultra-pure water This stage potentiallyremoves adsorbed secondary micro-phases Previousstudies (eg Lecuyer amp Reynard 1996) demonstratedthat pyroxene and amphibole can be intermixed on avery fine scale with other phases (such as a range ofamphibole compositions talc Fe-oxide) Although thispossibility cannot be ruled out the procedure used inthis study makes it unlikely that complex minerals passedthrough the selection

Sr isotopic compositions

Approximately 50mg of whole-rock powder or separatedminerals were digested in a Teflon lsquobombrsquo with a mixtureof triple distilled 13N HNO3 and 48 HF with a fewdrops of HClO4 Two aliquots were separated one forthe determination of Sr isotopic composition and theother for Sr and Rb contents Sr was separated using anextraction chromatographic method modified from Pinet al (1994) Concentrations were measured by isotopedilution using 84Sr---87Rb mixed spikes To remove tracesof the late low-temperature seawater alteration and todetermine the primitive whole-rock Sr isotopic composi-tion leaching experiments were conducted on a fewsamples following the procedure described by Bosch(1991) The strontium isotopic compositions of leachateshave been analysed in the attempt to check for the leach-ing efficiency During these tests four Sr isotope composi-tions were measured which correspond to the unleachedsample the two liquids extracted after acid-leaching stepsand the final solid residue Leaching experiments wereconducted in two steps first with 6N HCl for 8min at70C second with 25N HCl for 30min at 70C Afterleaching the leachates were evaporated to dryness andthe solid residues digested similarly to the unleachedsamplesSr isotopic compositions were measured on a fully

automated VG Sector mass spectrometer housed at theUniversity of Montpellier II except for the Sr isotopicdata from the leaching experiments which have beenmeasured at the Universitee de Bretagne Occidentale(Brest) To assess the reproducibility and accuracy of Srisotopic measurements the NBS 987 standard was run12 times during this study the average value was0710245 with a precision better than 0000010 (2s)87Sr86Sr ratios are corrected for mass discrimination bynormalizing to a 86Sr88Sr value of 01194 Sr total blankconcentrations were less than 60 pg Initial 87Sr86Sr


1189

ratios were calculated by correcting the measured ratiosfor accumulation of 87Sr produced by in situ 87Rb radio-active decay since 95Ma the assumed age of crystalliza-tion of the Oman ophiolite (Hacker 1994)

Oxygen isotopes

The powdered samples were introduced in Ni tubesunder dry air where they were reacted with BrF5 toform oxygen Oxygen was separated from other gasesby cooling the resulting mixture at liquid nitrogen tem-perature (77 K) that retained other volatile gases Oxygenwas further purified by trapping it on a cooled 5A mole-cular sieve at 77 K then quantified to calculate the yieldof the isotopic analyses and finally transferred to the massspectrometer (Finnigan Mat Delta E) where intensitiesassociated with masses 32 and 34 were measured todetermine d18O The isotopic composition of a sampleis given as dsample frac14 (RsampleRstandard 1) 1000 in permil unit where R is 18O16O and the standard isSMOW Analytical errors on the oxygen isotope ratioare 02 (2s)

RESULTS

Seven samples representative of the range of gabbroicdykes and five samples representative of the lower gab-bros two of them representing the margins of gabbroicdykes were selected for major element thermometricand Sr---O isotopic analyses (Tables 1---3) These samplesoriginate from wadi sections marked by bold lines inFig 1 Wadis Halhal Mayah Al Abyad Warihya andMaqsad structurally belong to a new ridge segment open-ing in slightly (1Myr) older lithosphere Wadi Gideahis in older lithosphere

Petrographic and isotopic characteristicsof the analysed samples

Olivine gabbro from the MTZ in MaqsadSamail Massif

Sample 94 MA2 is devoid of low-temperature alterationand only exhibits the discrete signature of the VHT---HTalteration The orthopyroxene corona around olivine(Fig 3a) is relayed by kelyphitic rims at the contactwith plagioclase (Fig 3b) Issuing from these rims aremicrometre-sized pale green amphiboles identified ascummingtonite and actinolite which penetrate the sur-rounding plagioclase in microcracks 004mm wide or atgrain boundaries (Fig 3b) similar to the microcrack sys-tem described by Manning et al (2000) A large numberof the plagioclase crystals have a cloudy core as a result ofthe concentration of fluid and mineral inclusions amongwhich diopside has been identified during microprobeanalysis Olivine cores are free of serpentine but theyare largely oxidized along a microcrack network Ortho-pyroxene coronas have a MgOpx number of 78---79

slightly higher than in the primary olivine cores withMgOl number of 74---75 The magmatic clinopyroxeneis totally fresh and probably not in equilibrium with thereactive orthopyroxene This sample has the lowest 87Sr86Sr initial ratio of the studied whole rocks (070322)identical to coexisting clinopyroxene (070324) and pla-gioclase (070322) This observation suggests the lack of alate superimposed LT hydrothermal alteration as it isvery unlikely that an LT hydrothermal event could havetotally equilibrated the Sr isotopic compositions of prim-ary minerals such as plagioclase and clinopyroxeneMoreover the whole rock (WR) clinopyroxene andplagioclase have similar initial Sr isotopic ratios despitevery different Sr contents Accordingly this ratio isthought to reflect the signature acquired during the crys-tallization of these minerals and is higher than the Omanmantle Sr isotopic value (McCulloch et al 1981) Thed18O values of the WR (50) and plagioclase (48) aredistinctly lower than primary magmatic values Indeedin normal mid-ocean ridge basalts (MORB) the WRd18O value is 57 02 with a corresponding plagio-clase d18O ranging from 55 to 62 ( Javoy 1980Gregory amp Taylor 1981)

Lower gabbro from Wadi Wariyah Wadi Tayin Massif

Sample 97 OA128b belongs to a layered sequence in thelower gabbro series injected by anorthositic sills Thesample was collected at the tip of one of these sillsbetween layers enriched in clinopyroxene The gabbrois composed of 60 plagioclase and 40 clinopyroxeneDespite the absence of olivine the WR has a relativelyhigh Mg content (Table 3) A series of low-T (prehnite)microveins 01mm thick cross-cut the gabbro perpendi-cular to the layering and foliation The margins of theveins are devoid of alteration This gabbro has the sameSr isotopic composition as 94 MA2 Nevertheless theWR and associated plagioclase have Sr isotope signatures(070333 and 070328) lower than the coexisting clino-pyroxene (070422) The Sr contents of the WR plagio-clase and clinopyroxene are 127 ppm 120 ppm and20 ppm respectively thus making the clinopyroxenemore sensitive to late-stage contamination Clinopyrox-ene and plagioclase oxygen isotope compositions (523and 414 respectively) are also lower than typicalmantle values Similar to the previous sample alterationat high temperature by a low d18O and high 87Sr86Srfluid is required to explain such characteristics

Amphibole gabbro patch Wadi Gideah Wadi TayinMassif

Sample 01 OA41d2 is from a laminated gabbro com-posed of millimetre-sized layers of clinopyroxeneand plagioclase Anatectic patches (Fig 7a) borderinganorthositic layers are formed of coarse-grained


1190

Table1Locationoftheanalysed

samplesandsummaryoftheirpetrographicandSr---O

isotopiccharacteristics

Sam

ple

nam

eSite

Locationin

gab

broic

section

Typ

eofrock

Distance

to

Moho(km)

Parag

enesis

Alteration

87Sr

86Srinitial1

d18O

()2

94MA2

Maq

sad

From

MTZ

Layered

gab

bro

0Olivine(M

gno74---75)3

OPXco

ronas

(Mgno78---79)

WRfrac14

070322

WRfrac14

thorn495

CPX

Palegreen

Am

(cumact)

CPXfrac14

070324

nd

Plagioclase(A

n65---80)4inversezoning

Nolow-T

alteration

Plfrac14

070322

Plfrac14

thorn479

Solidfluid

inclusionsin

Pl

97OA128b

Wad

iWaryiah

From

lower

gab

bro

Layered

gab

bro

1CPX

Low-T

alteration

WRfrac14

070333

nd

Plagioclase(A

n85---87)

Prehnitemicroveins

CPXfrac14

070422

CPXfrac14

thorn523

Plfrac14

070328

Plfrac14

thorn414

01OA41d2

Wad

iGideah

From

upper

gab

bro

Gab

bro

patch

in

laminated

gab

bro

36

CPXrecrystallized

Plagioclaseidiomorphic

(An57---87)norm

alzoning

Black

pargasitic

honblende

WRfrac14

070351

CPXfrac14

070378

Plfrac14

070426

WRfrac14

thorn480

nd

Plfrac14

thorn504

Hbdfrac14

070355

nd

01OA19aamp

dWad

iWaryiah

Inlayeredgab

bro

Gab

broic

dyke

01

Olivine

OPXpoikilitic

WRfrac14

070341

WRfrac14

thorn567

CPX

Black

pargasite

Hbdfrac14

070324

Hbdfrac14

thorn287

Plagioclase(A

n73---95)

Hornblendepoikilitic

Plfrac14

nd

Plfrac14

thorn10 09

Hem

atite

WRfrac14

070418

nd

Green

Mg-hornblende

Acthornblende

Epidote

02OA90b

Wad

iAl-Abyad

Inlayeredgab

bro

Dioriticdyke

015

Green

Mg-hornblende

Hbdfrac14

070427

Hbdfrac14

thorn239

Plagioclase(A

n83---87)

Plfrac14

070387

Plfrac14

thorn498

Solidfluid

inclusionsin

plagioclase

01OA15f

Wad

iWaryiah

Inlayeredgab

bro

Comb-textured

gab

broic

dyke

025

CPXidiomorphic

Plagioclase(A

n95---99)norm

alzoning

BrownMg-H

ornblende

WRfrac14

070458

nd

02OA43a

Wad

iMayah

Inlayeredgab

bro

vein

Green

amphibole

1Palegreen

Mg-hornblendeacicular

Plagioclase(A

n91---97)in

reactionmargin

Hbdfrac14

070431

Hbdfrac14

thorn310

01OA36b

Wad

iGideah

Inlayeredgab

bro

epidosite

dyke

25

CPX

Epidote

WRfrac14

070519

nd

Plagioclase

Epfrac14

070554

nd

CPXclinopyroxene

Plplagioclase

OPXorthopyroxene

Amam

phibolecu

mcu

mmingtonite

actactinolite

WRwholerockHbdhornblende

Epep

idotend

notdetermined

187Sr

86Srinitialratioscalculatedat

95Ma(H

acker1994)Errors

ofthemeasuredratiosareindicated

inTab

le4

2Analyticalerrors

oftheoxygen

isotopevalues

are02

(2s)

3Mgnumber

frac14atomicMg(Mgthorn

Fe)

4Percentageofan

orthitein

plagioclase


1191

(millimetre-sized) recrystallized clinopyroxene largelyaltered to light green magnesio-hornblende and idio-morphic plagioclase Locally primary black pargasitichornblende develops including idiomorphic normallyzoned plagioclase (Table 4) This gabbro exhibits similar87Sr86Sr ratios for the WR and pargasite (070351 and070355 respectively) These values are interpreted asrepresentative of the melt from which this amphibolecrystallized The clinopyroxene has a slightly higher Srisotope composition of 070378 consistent with the occur-rence of the light green Mg-hornblende rim Plagioclaseis significantly more radiogenic (070426) related to sec-ondary destabilization evidenced by the idiomorphichabit The Sr isotope compositions of the liquidsextracted from the acid leaching experiments of theWR (L1 and L2) are very similar 070358 and 070365respectively The 87Sr86Sr ratio of the residue obtainedafter leaching experiments is 070335 lower than boththe pargasite and unleached WR This value can beconsidered as the unaltered isotopic composition of thissample The d18O values measured for WR and coexist-ing plagioclase are lower than normal MORB magmaticvalues The 18O depletion in the plagioclase can be fairlywell explained by high-temperature hydrothermal inter-action between an oxygen-depleted fluid and the magmaAccording to the kinetics of hydrothermal exchange ofoxygen (Gregory amp Taylor 1981 Gregory et al 1989)plagioclase exchanges its oxygen isotopes with the fluidadjusting readily to the hydrothermal conditions Forhigh temperatures of exchange with seawater-derivedfluids (d18O between 0 and thorn2) the magmatic plagio-clase will have its primary d18O value lowered whereasthe d18O value for lower temperatures of exchange(5300C) will increase The amplification of the d18Oshift increases with the intensity of the hydrothermalalteration

Gabbroic dykes intrusive in lower gabbros from WadiWariyah Wadi Tayin Massif

Gabbroic dykes 01 OA19a and 01 OA19d are intrusiveinto the lower gabbros They are 3---4 cm wide discord-ant to the foliation of the host gabbros (Fig 7e) with asharp margin marked by a brown amphibole fringe Theprimary phases in the dykes (Table 1) locally preservedas elongated aggregates of a 01mm grain size mosaicassemblage at the dyke margins grade to millimetre sizein the central part of the dyke The WR major elementcomposition is Mg enriched compared with the enclosinggabbro (Table 3) Brown pargasitic amphibole oikocrystsmake up 50 of the modal composition of the dyke Indyke 01 OA19a poikilitic orthopyroxene may developinstead of brown amphibole Finally green magnesio-hornblende grows either as oikocrysts at the expense ofclinopyroxene or in association with epidote as an altera-tion product of plagioclase These low-amphibolite-faciesminerals represent the lowest-grade paragenesis recogn-ized in these dykes and are most developed in sample01OA19aTheamphibole composition showszoning fromTi-rich pargasitic hornblende to magnesio-hornblendeand actinolitic hornblende (Fig 8c) recording pro-gressive cooling of the dyke The plagioclase compositionis extremely heterogeneous (Fig 8b) varying from An95a composition similar to that of the plagioclase in the hostgabbro (Fig 8a) to An50 for the plagioclase and asso-ciated epidote inclusions in the poikilitic actinolitic horn-blende Sample 01 OA19d has an initial 87Sr86Sr ratioslightly higher for the WR (070341) than for the parga-site (070324) The Sr isotopic ratios of liquids extractedafter two steps of WR acid-leaching (L1 and L2) are070357 and 070341 respectively whereas the residueyields a 87Sr86Sr ratio of 070327 very close to thepargasite and plagioclase values The latter is similar tothe isotopic composition measured for the massive gab-bro 94 MA2 and may be taken as close to the primarymagmatic value This Sr isotopic ratio is more radiogenicthan the inferred Oman mantle-source value (McCullochet al 1981) The altered part of this sample has a radio-genic Sr isotopic composition (070418) related to thelow-amphibolite-facies alteration This gabbroic dykehas seemingly preserved a magmatic whole-rock d18Ovalue (567) but contains by far the highestd18O plagioclase (1009) of all the samples analysedThis plagioclase coexists with low d18O pargasite(thorn287) Similarly high values (d18Oplagioclase 4 8)have been previously measured for gabbroic dykes dia-bases sheeted dykes and plagiogranites from the Omanophiolite (Gregory amp Taylor 1981 Stakes amp Taylor1992) This 72 oxygen isotope fractionation betweenplagioclase and amphibole cannot possibly represent oxy-gen equilibrium at any plausible temperature This maybe explained by different exchange kinetics for these twominerals at different temperatures at high waterrock

Table 2 Average temperatures ( C 40C)

calculated for plagioclase---amphibole pairs

using the geothermometer of Holland amp

Blundy (1994)

Pargasite Magnesio-hornblende

rim core rim core

01 OA41d2 878 953 ------- -------

01 OA19a 935 974 825 869

01 OA19d 890 933 789 -------

02 OA37b ------- ------- 816 849

02 OA90b ------- ------- 859 833


1192

ratios This supports the occurrence of two distincthydrothermal events one at high temperature and alater stage at lower temperature responsible for thestrong 18O enrichment in the coexisting plagioclase

Dioritic dyke associated with a diabase dyke in lowergabbros from Wadi Halhal Haylayn Massif

Sample 02 OA37b belongs to a group of brownamphibole---plagioclase lenses or reaction margins asso-ciated with diabase intrusives (Fig 7d) in lower layeredgabbros Idiomorphic brown hornblende (tschermakite)crystals are elongated in the plane of the dyke represent-ing 80 of the modal composition They are associatedwith an interstitial plagioclase matrix The browntschermakite has greenish rims Plagioclase has a cloudyappearance due to micrometre-size fluid inclusionsexcept along its margins and internal microcracks Bothhornblende and plagioclase exhibit evidence of plasticdeformation The Sr isotopic ratio for the pargasite andplagioclase is 070348 and 070420 respectively Thepargasite exhibits a Sr signature closest to that of theOman primary magmatic value (McCulloch et al 1981)Nevertheless it is too high to be attributed to anunmodified MORB-source mantle signature This sug-gests the addition of an external fluid component in goodagreement with the shift of oxygen isotopic compositionto a low value (thorn39) suggesting a high-temperatureexchange with a low d18O fluid The Sr isotope composi-tion of the plagioclase is significantly higher than that of

the coexisting pargasite probably as a result of the low-temperature alteration

Dioritic dyke cross-cutting lower layered gabbros in WadiAl-Abyad Nakhl Massif

Sample 02 OA90b is a 1 cm thick dioritic dyke cross-cutting the lower layered gabbros It grades into a greenamphibole vein as illustrated in Fig 6c The dyke is com-posed of 2 cm long dark green idiomorphic magnesio-hornblende crystals growing in the plane of the dykeand plagioclase concentrated at the margin of the dykeThe plagioclase in the dyke and in the enclosing gabbrocontains micrometre-size fluid and mineral inclusionssimilar to those observed in sample 94 MA2 The plagio-clase and green hornblende have higher Sr isotopic ratios(070387 and 070427 respectively) and lower d18Ovalues (thorn498 and thorn239 respectively) than the normalMORB-source mantle value As observed for previoussamples this supports interaction with an external fluidcomponent

Comb-textured gabbroic dykes in the lower gabbros fromWadi Wariyah Wadi Tayin Massif

Sample 01 OA15f (Fig 6b) is from Wadi Wariyah andrepresents a 2 cm wide dyke intruding the lower gabbrosThis type of comb-textured dyke developed in theclinopyroxene---plagioclase stability field It containslarge idiomorphic clinopyroxene crystals which arepartially replaced by brownish magnesio-hornblendeThe plagioclase is extremely calcic with a slight inverse

Table 3 Whole-rock major element compositions of massive gabbros and dykes determined by X-ray fluorescence

(wt )

Sample 94 Ma2 97 OA128b 01 OA41d2 01 OA19d 01 OA19a 01 OA15f 01 OA36b 01 OA36b

Rock type Gabbro Gabbro Gabbro patch Gabbroic dyke Gabbroic dyke Comb-textured

gabb dyke

Epidosite dyke Epidosite dyke

(margin)

SiO2 4830 4815 4749 4524 4339 4799 389 4371

Al2O3 2785 2032 2438 1474 1246 1192 2752 1646

Fe2O3 328 266 404 981 1204 592 381 623

MnO 003 004 005 014 016 006 008 014

MgO 405 737 427 1031 1686 1326 187 739

CaO 1289 1908 1477 1235 1156 166 2471 2339

Na2O 292 123 257 258 111 075 000 013

K2O 000 000 009 006 000 000 000 000

TiO2 005 017 063 230 064 086 013 042

P2O5 008 007 013 018 009 013 007 010

LOI 033 076 138 216 161 237 274 190

Total 9978 9985 998 9987 9992 9986 9983 9987

LOI loss on ignition gabb gabbroic


1193

Table4Majorelementcomposition

aofselectedam

phibolespaired

withplagioclasecompositionsusedforthermometry

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

01OA19a

Mg-hornblende

core

45 60

26

10 78

009

860

015

16 56

12 00

212

007

96 72

6552

1448

0366

0083

0552

0004

3409

0594

0016

0611

0018

1843

0903

899

Mg-hornblende

core

47 99

263

850

002

897

011

16 61

12 10

160

020

96 36

6894

1106

0334

0028

0483

0002

3557

0594

0014

0446

0036

1862

0892

834

Mg-hornblende

rim

51 17

247

596

001

761

014

18 11

12 19

103

010

96 47

7257

0743

0253

0016

0414

0001

3828

0488

0016

0284

0018

1853

0894

820

Mg-hornblende

rim

47 50

291

920

004

880

014

16 46

11 95

174

008

96 07

6835

1165

0396

0015

0506

0005

3529

0552

0017

0486

0015

1843

0887

825

Mg-hornblende

rim

49 57

269

742

000

799

017

18 07

12 02

133

014

96 88

7013

0987

0261

0018

0575

0000

3811

0371

0020

0365

0026

1821

0860

831

Mg-hornblende

core

47 83

181

872

003

840

011

14 48

12 18

159

008

93 59

6814

1186

0279

0018

0644

0004

3711

0357

0013

0438

0015

1859

0907

874

Pargasite

rim

42 15

249

11 87

024

10 07

013

13 84

11 43

263

032

96 61

6188

1812

0242

0434

0299

0028

3028

0937

0016

0749

0059

1797

0804

972

Pargasite

rim

42 22

260

11 86

026

10 21

011

13 71

11 48

253

032

96 59

6201

1799

0254

0429

0299

0030

3001

0955

0014

0720

0060

1807

0803

962

Pargasite

core

42 05

263

11 45

030

10 19

011

13 80

11 47

246

032

96 46

6189

1811

0175

0478

0299

0035

3029

0956

0014

0702

0060

1809

0767

974

Pargasite

rim

42 36

247

11 90

016

945

013

14 16

11 76

249

026

95 98

6239

1761

0305

0366

0276

0019

3109

0888

0016

0710

0049

1856

0818

926

Pargasite

core

42 50

291

11 64

016

984

015

14 22

11 41

256

034

96 69

6219

1781

0227

0426

0322

0018

3103

0883

0018

0727

0063

1789

0812

974

Pargasite

rim

42 76

270

12 03

017

920

012

14 87

11 82

244

025

96 73

6224

1776

0880

0335

0368

0020

3226

0752

0015

0689

0047

1843

0841

941

Pargasite

rim

42 13

181

13 54

016

921

009

12 77

12 13

254

032

96 98

6172

1828

0510

0450

0000

0018

2788

1129

0011

0721

0059

1905

0841

874

01OA19d

Mg-hornblende

49 26

047

624

011

11 46

017

15 39

12 21

108

009

96 48

7137

0863

0202

0051

0437

0013

3323

0951

0021

0302

0018

1896

0768

771

Mg-hornblende

46 03

287

932

018

906

017

14 77

12 87

193

007

97 28

6672

1328

0265

0313

0046

0021

3191

1053

0021

0542

0012

1999

0758

808

Pargasite

41 89

429

11 65

008

11 03

017

13 52

11 37

259

017

96 77

6159

1841

0179

0474

0345

0010

2963

1012

0021

0739

0032

1791

0770

975

Pargasite

rim

42 80

340

11 16

009

11 01

018

13 73

11 67

240

022

96 67

6293

1707

0226

0376

0322

0010

3009

1032

0022

0684

0041

1839

0605

880

Pargasite

core

42 58

351

11 27

006

11 63

018

13 51

11 46

239

022

96 82

6257

1743

0209

0387

0391

0007

2959

1039

0023

0680

0042

1804

0595

893

Pargasite

rim

42 14

393

11 28

006

11 71

014

13 35

11 33

235

033

96 62

6214

1786

0174

0435

0391

0007

2935

1054

0018

0673

0062

1790

0519

901

Pargasite

core

41 56

420

12 05

006

11 57

016

12 51

11 35

249

027

96 24

6168

1832

0277

0469

0276

0007

2768

1160

0021

0718

0052

1805

0537

882

Pargasite

core

41 33

438

11 49

008

11 66

015

13 35

11 45

264

026

96 80

6105

1894

0107

0487

0368

0009

2941

1073

0019

0757

0048

1813

0537

942

Pargasite

41 08

446

12 39

012

11 35

017

13 13

11 36

263

015

96 85

6049

1951

0199

0494

0368

0014

2882

1030

0021

0752

0027

1792

0758

975

02OA37b

Mg-hornblende

rim

45 15

260

984

002

13 28

019

14 01

10 87

128

009

97 33

6527

1473

0203

0283

0690

0002

3018

0915

0023

0360

0016

1683

0562

828

Mg-hornblende

rim

44 72

263

988

004

13 23

021

14 01

10 78

133

009

96 92

6494

1506

0185

0287

0713

0005

3032

0894

0025

0374

0018

1677

0593

854

Mg-hornblende

rim

45 68

247

935

004

12 87

020

14 10

11 00

121

011

97 02

6621

1379

0218

0269

0598

0004

3045

0962

0024

0341

0020

1708

0562

815

Mg-hornblende

core

43 94

291

10 87

001

12 60

023

13 73

10 59

142

011

96 39

6410

1590

0278

0319

0644

0001

2985

0893

0028

0401

0021

1655

0710

860

Mg-hornblende

core

44 62

270

10 37

001

12 66

019

14 12

10 58

140

008

96 73

6479

1521

0253

0294

0644

0001

3057

0893

0023

0395

0014

1646

0674

851

Mg-hornblende

rim

47 79

181

796

002

12 09

025

15 22

11 09

100

009

97 33

6866

1134

0214

0196

0506

0002

3260

0947

0030

0280

0016

1706

0503

767

Mg-hornblende

core

45 43

249

10 3

000

11 99

022

14 50

11 14

133

008

97 48

6524

1476

0267

0269

0644

0000

3103

0796

0027

0370

0015

1715

0703

838


1194

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein

weightpercent-------noplagioclasean

alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam

phibole---plagioclasepaircalculatedusingtheHollandamp

Blundythermometer

(1994)Errors

are40

C


1195

zonation from An95 to An99 from core to rim (Table 1 andFig 8a) TheWR Sr isotopic ratio of the sample (070458)is significantly higher than normal MORB values Thiscould be related to the overprint of a low-temperaturealteration event consistent with the petrography of thesample

Green amphibole vein cross-cutting layered gabbros inWadi Mayah Haylayn Massif

Sample 02 OA43a belongs to a series of 1 cm thick greenamphibole veins (as in Fig 6e) cross-cutting the layeredgabbros The veins develop 15 cm thick reaction marginsin the enclosing gabbro and are exclusively composed ofacicular pale green magnesio-hornblende growing per-pendicular to the vein margin in a crack-seal mode(Fig 6f ) The reaction margins are composed of urali-tized gabbro marked by the development of the samepale green magnesio-hornblende in an inhomogeneouscalcic plagioclase matrix (An91---97) The Sr and O isotopiccompositions of this green hornblende (070431 andthorn31) do not correspond to normal MORB-sourcemantle values

Epidosite dyke from Wadi Gideah Wadi Tayin Massif

Sample 01 OA36b is representative of a series of epidoteveins cross-cutting poorly layered gabbros These 2 cmthick veins are composed of pink thulite in their centreand green pistachite at their margins (Fig 6a) Theirsharp contact with the enclosing gabbro is marked bythe development of coarse clinopyroxene crystals alteredin the epidote---greenschist facies This suggests that theepidote vein is replacive in a coarse-grained gabbro dykeThe highest 87Sr86Sr initial ratios of all the samplesstudied are recorded by the WR and coexisting epidoteof this sample (070519 and 070554 respectively)(Table 5) The Sr content of the WR and associatedepidote are also the highest of the present dataset(716 ppm and 764 ppm respectively) The Sr isotopiccomposition of this sample is consistent with a greaterdegree of exchange with a radiogenic component fromCretaceous seawater It is significantly higher than thevalue obtained for an epidosite vein from the Wadi Fizhsection of the Oman ophiolite [070435 with a Sr contentof 488 ppm reported by Kawahata et al (2001)] but ingood agreement with the average of the greenschist-faciesalteration sequence defined by Kawahata et al (2001)

GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)

Distance to the Moho

ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE

PARGASITEGabbros Dykes41d2MA2

19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV

Fig 8 Plagioclase---amphibole compositions and results of thermometry (a) and (b) plagioclase compositions in layered gabbros and in dykesrespectively as a function of distance to the Moho (see text for sample identification) (c) amphibole compositions in layered gabbros and dykesaccording to Leakersquos (1997) nomenclature (d) equilibration temperatures calculated using the amphibole---plagioclase thermometer of Holland ampBlundy (1994) as a function of AlIV content in amphibole [same symbols as in (c)]


1196

Table5RbandSrcontents87Sr

86Srandd1

8Oisotopiccompositionsofwholerocksandmineralseparatesfrom

samplesofmassivegabbrosdykes

andveinsfrom

theOman

ophiolitealsolistedarecalculated

waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr

86Srratiocalculatedat

95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock

ratiocalculatedassumingaclosedsystem

TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=

86SrseawaterTHORN in

itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr

86Srrock) finalisthefinalmeasuredSrisotopicratioin

thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in

itialistheCretaceousseaw

ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco

ncentrationmeasuredis

thesameas

theinitial

concentration

4Srisotopicratiosmeasuredforliquid

L1extractedafterthefirststep

oftheleachingexperim

ent(6NHClfor8min

at70

C)


L2extractedaftertheseco

ndstep


ent(2 5NHClfor30

min

at70

C)

6Srisotopicratiosmeasuredforresidueobtained

afteratotalaciddigestionachievedaftertheextractionofL1an

dL2leachates


1198

Part of the same sample from the contact between thedyke and the gabbro yields a slightly lower Sr isotopiccomposition (070464) intermediate between the sur-rounding gabbro and the epidote dyke It also has anintermediate Sr content (425 ppm) Acid leaching experi-ments performed on the whole rock of the dyke yield Srisotopic compositions of 070521 and 070512 for thetwo liquids extracted Similar experiments for the samplelocated at the contact with the gabbro yield 87Sr86Srratios of 070494 and 070467 for L1 and L2 liquids TheSr isotopic composition of the residue extracted afterleaching remains high (070459) and very close to theepidosite 87Sr86Sr ratio determined by Kawahata et al(2001) In this sample the primary minerals have beentotally replaced by epidote and secondary plagioclase orquartz Thus the Sr isotopic compositions measured forthis WR sample and its constituent minerals reflect thecomposition of the fluid filling this dyke

Mineral chemistry

Plagioclase

Compared with the host gabbros the dykes show a muchlarger dispersion in their plagioclase compositions (Fig 8aand b Table 4) characterized by more calcic plagioclasethan the enclosing gabbros This tendency is mostextreme in the comb-textured dykes in which the plagio-clase is almost pure anorthite The zoning is generallynormal recording a crystal fractionation process How-ever gabbro 94 MA2 exhibits inverse zoning this tend-ency is also observed in plagioclases from dykes 01OA19a and 01 OA15f The higher calcium content ofthe plagioclase as well as the inverse zoning is consistentwith an increase of water pressure during its crystalliza-tion (Turner amp Verhoogen 1960 Carmichael et al 1974Koepke et al 2003) The particularly high An content inthe comb-textured gabbro dykes 01 OA15f may alsoresult from crystallization in a supercooled magma thisis consistent with the comb texture indicative of fast-growing crystals The lack of brown hornblende suggeststhat crystallization occurred above the temperature ofhornblende stability

Amphibole

The amphiboles analysed in the dykes (Fig 8c andTable 4) show a regular trend in a (Na thorn K)A vsAlIV diagram from titanium-rich (Ti 4 015) pargasitichornblende (brownamphibole) and tschermakite (brown---green amphibole) to low-titanium (Ti5 015) magnesio-hornblende (green amphibole) and actinolite (pale greenamphibole) The pargasitic hornblende develops aspoikilitic oikocrysts in the dykes 01 OA19a and d andin the diffuse patch 01 OA41d2 at temperatures above800C during the final stage of crystallization (see

below) The tschermakite composition corresponds tothe internal alteration of clinopyroxene in gabbro 94Ma2 occurs in the comb-textured dyke 01 OA15f andis the primary amphibole in the dioritic dyke 02 OA37bThe magnesio-hornblende develops at the edges of thepargasites or of clinopyroxenes at temperatures around800C and is the primary phase in the dioritic dyke 02OA90b and in the green vein 02 OA43a Finally actino-lite occurs as a replacement of green hornblende in dykesor in the kelyphitic rim surrounding olivine in gabbro 94Ma2 Such a large composition range at the scale of athin section has been reported in amphiboles fromamphibolite-facies oceanic gabbros (Stakes 1991 Stakesamp Taylor 1992 Gillis et al 1993) as well as in the Omanophiolite gabbros (Manning et al 2000) This variabilityhas been explained by rapid reaction rates preventinghomogenization (Manning et al 2000)

Thermometry

Plagioclase---amphibole thermometry could be appliedwhen the two minerals exhibited good contacts such asin the laminated gabbro of the middle sequence (01OA41d2) and in the intrusive dykes The temperaturesof plagioclase---amphibole equilibration (Table 2) havebeen calculated using the geothermometer lsquoBrsquo of Hollandamp Blundy (1994) Edenite thorn Albite frac14 Richterite thornAnorthite valid between 500C and 900C with anuncertainty of 40C Amphibole formulae are basedon 23 oxygen and their nomenclature is based on alkalications in the A site vs AlIV according to Leake (1997)Pressurewas assumed to be 1 kbar Forty-five plagioclase---amphibole pairs meet the compositional criteria imposedby Holland amp Blundyrsquos dataset (09 4 Xan 4 01 andAlIV 403) Electron microprobe measurements wereconstrained to contiguous plagioclase and amphiboleseparated by sharp grain boundaries assuming equili-brium of the two phases When the mineral phasesexhibit normal zoning temperatures between plagioclaseand amphibole cores and between mineral rims werecalculated assuming that the temperatures deduced fromthe mineral core chemistry provide a proxy for the high-est temperature of equilibration These data are identi-fied in the T C vs AlIV diagram (Fig 8d) Table 4presents selected major element amphibole analyses theAn content of the plagioclase adjacent to each amphibolegrain and the temperature calculated for the pairThe temperatures calculated (Fig 8d) span the entire

range of temperatures at which amphibole and plagio-clase coexist in equilibrium (ie amphibolite-facies para-geneses) This temperature interval is bracketed byorthopyroxene-bearing facies or amphibole-free facies(ie gabbro 94MA2) and epidote---actinolite facies devoidof homogeneous plagioclase (ie epidosite dyke 01OA36b and green vein 02 OA43a) The range of the


1199

calculated temperatures between 4900C and 750Ccorresponds to the changing composition of amphibolesfrom pargasite to magnesio-hornblende at the scale of athin section or even at that of an individual crystal asshown by their correlation with AlIV such variabilityrecords rapid cooling in hydrous conditions The highesttemperatures are recorded by pargasite from the anatec-tic gabbro 01 OA41d2 in the gabbro dyke 01 OA19dand in the dioritic dyke 02 OA90b They were calculatedfrom minerals devoid of lower-grade alteration and arethus considered as representing the equilibrium temperat-ure of the coexisting minerals Lower temperatures cor-respond to mineral phases evolving at falling temperatureand are only indicative of the cooling history Includingthe 40C uncertainty seven pairs provide temperatureshigher than 900C the limit of validity of the Holland ampBlundy thermometer However we maintain these tem-peratures as indicative of the highest values of our data-set These values are included in the average equilibriumtemperature summarized in Table 2

DISCUSSION

Distribution of hydrothermal alteration

Two distinct petrological events are recorded in the gab-bro section of the Samail ophiolite and are documentedin the present contribution (1) the whole gabbro sectionis affected by a penetrative alteration (2) the gabbrosection is crosscut by various types of dykes and veinsincluding hydrous minerals

Penetrative alteration

The penetrative alteration developed in the gabbros atgrain boundaries and locally invading the minerals isubiquitous in the gabbro section This penetrative altera-tion has been described as very high temperature (VHT)high temperature (HT) and low temperature (LT) basedon alteration parageneses The orthopyroxene coronas inthe layered gabbro sample and the incipient appearanceof brown pargasitic amphibole mark a lower thermallimit of the VHT alteration By reference to the experi-mental work of Koepke et al (2003) the temperature ofequilibration for these reactions is estimated to bebetween 900 and 1000CThe preservation of the vertical distribution of

VHT---HT facies (Figs 4 and 5) also pointed out byManning et al (2000) indicates that the hydrothermalalteration pattern fits the distribution of isotherms withdepth at a fast-spreading ridge (ie Phipps Morgan ampChen 1993 Dunn et al 2000 Fig 2) Equilibrium tem-peratures for VHT parageneses as high as 900---1000Csuggest that VHT---HT hydrothermal alteration tookplace in a very restricted time interval at the limit ofthe cooling magma chamber It is proposed that the

penetrative alteration affecting the entire gabbro sectionis related to a pervasive network of microcracks whichact as a recharge system down to the Moho (Nicolas et al2003)

Dykes and veins

The dykes are extremely varied eg pegmatitic gabbroswith comb-texture microgabbros and amphibolitizeddolerites dioritic dykes alignments of poikilitic horn-blende and finally diffuse hornblende-bearing patchesHigh-T gabbro and diorite dykes and low-T greenamphibole---epidote veins are connectedIn the dykes textural evidence attests to suprasolidus

conditions at least for the development of the pargasiticamphibole Integrating the hornblende---plagioclase equi-libration temperatures calculated for the studied samplesthese temperatures are bracketed between 950C and875CIn the following discussion we shall consider separately

the microgabbro and dolerite dykes The latter representbasaltic melt intrusions associated upsection with thediabase sheeted dykes and downsection possibly withthe mafic dykes that are ubiquitous in the mantle section(Nicolas et al 2000) Whatever their origin the develop-ment of pargasitic amphibole during their late stage ofcrystallization creates a link with the gabbroic dykes andsuggests a crystallization process evolving from dry con-ditions to more hydrous conditionsThe other gabbroic dykes comb-textured gabbros and

hornblende-bearing dioritic dykes result from the fillingof cracks by a fluid either a melt or a silica-rich hydrousfluid These intrusive dykes which develop reaction mar-gins at their contact with the host gabbro grade verticallyinto lower-temperature green amphibole veins or align-ments of poikilitic hornblende in the layered gabbromatrix or development of pargasitic hornblende in ana-tectic gabbros (sample 01 OA41d2) In gabbros crystal-lizing in the magma chamber the development oforthopyroxene and pargasite oikocrysts enclosing the pri-mary minerals suggests a thermal evolution from thegabbro solidus to amphibolite-facies conditions Forthese reasons it is suggested that the gabbroic dykesresulted from the injection of a hydrous melt in the stillhot gabbros drifting away from the magma chamber asdiscussed below

Origin of fluids responsible for VHT---HThydrothermal alteration

The 87Sr86Sr initial ratios and d18O of whole rocks andpure mineral fractions are plotted in Fig 9 against thedistance above the Moho Transition Zone (MTZ) Theinitial Sr isotopic composition of the whole rocks apartfrom the epidosite dykes ranges from 070322 to


1200

070458 All the studied samples (including whole rocksand minerals) have initial 87Sr86Sr ratios falling outsidethe field of fresh MORB which commonly have Sr ratiosbetween 07023 and 07029 with an average of 070265(ie Hart et al 1974) The lowest initial Sr isotopiccomposition (070322) from the massive gabbro 94MA2 is slightly but significantly higher than averageOman primary magmatic signatures (ie 070296McCulloch et al 1981) Similarly the d18O values ofmost whole rocks and minerals measured (Table 5)

depart from typical MORB-source mantle values( Javoy 1980 Gregory amp Taylor 1981 Kyser 1986)These differences indicate that the primary mantlesignatures in the Oman ophiolite have been modifiedby interaction with a fluid Possible origins for thisfluid are mantle components dehydration of subductedlithosphere or seawater circulation Strontium andoxygen isotopes are useful tracers for fluid---crust interac-tion as d18O and 87Sr86Sr ratios from fluids originat-ing from seawater the mantle or subducted lithosphere

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater

Whole RockPlagioclasePargasiteGreen HornblendeClinopyroxene

Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)

Fig 9 (a) Variation of initial 87Sr86Sr isotopic composition as a function of the location of the studied samples in a schematic log of the crustalsection of the Oman ophiolite The field for MORB is from Hart et al (1974) and that for seawater is from Burke et al (1982) Small open squares aredata fromKawahata et al (2001) (b) Variation of d18O () as a function of the location of the studied samples in a schematic log of the crustal sectionof the Oman ophiolite Shaded curve corresponds to the data of Gregory amp Taylor (1981)


1201

are significantly different Moreover the d18O valueis dependent on temperature and mineral fractiona-tion and thus yields complementary constraints to Srisotopes

Mantle origin

One model to explain the occurrence of fluids interactingwith the oceanic crust at very high temperatures is toderive them from the mantle The contribution of mantle-derived hydrous fluids linked to percolation processesor to their concentration in the final stages of gabbrocrystallization has been invoked in numerous case studies(ie Witt amp Seck 1989 Fabriees et al 1989 Dupuy et al1991 Agrinier et al 1993) O and Sr isotopic data forwhole rocks and mineral separates yield scattered valuesthat are unambiguously different from MORB mantle-source values (Fig 9a and b) With the exception of lateLT altered samples the WR data have a mean 87Sr86Srratio of 070337 and a standard deviation of 000012These surprisingly high values in mantle-derived rockscould be taken as evidence for survival of mantle isotopicheterogeneities during crystallization of the ophiolite (egLanphere 1981 McCulloch et al 1981) However the18O16O isotope ratios in the Oman gabbroic sequenceare also displaced from primary magmatic values Nogabbro in the present study has plagioclase or amphi-bole with typical mantle d18O values Thus the Sr and Oisotope data rule out the possibility of mantle-derivedfluids as a possible source for the VHT---HT hydrousalteration event recorded in the massive gabbros andgabbroic dykes and veins (Fig 10a and b)

Subducted lithosphere origin

Dehydration of subducted oceanic crust in subductionzones can generate hydrous fluids Such fluids couldpercolate through the overlying lithosphere and contam-inate it thus generating modified isotopic signatures andtrace element contents Such an explanation howeverdisagrees with the geochemical characteristics of most ofthe studied samples Fluids derived from the dehydrationof subducted slabs (fresh or altered MORB or OIB pro-toliths) should be strongly enriched in K Rb and Ba (egBecker et al 2000) whereas in Oman the Rb contentsmeasured in the gabbros and gabbroic dykes and veins arestrongly depleted Moreover the isotopic composition ofslab-derived fluids is buffered by the MORB-like oceaniccrustal protolith for Nd and Pb but not for Sr and O(Staudigel et al 1995) As a result of relatively minorfractionation of oxygen at high temperature the oxygenisotope composition of the fluids expelled during dehy-dration of the subducted slab should be high and essen-tially controlled by the oxygen composition of the uppersection of the crust altered at low temperature (with an

average of 10 and perhaps as high as 19) (Staudigelet al 1995) The Sr isotopic composition should be alsohigh (average 07046) as the fluids released by the dehy-dration of subducted oceanic crust are associated eitherwith seawater or with radiogenic Sr phases (ie smectites)The Sr and O isotopic compositions of the studied sam-ples do not fit with these signatures and so preclude asubducted lithosphere origin for the fluids involved in theVHT---HT alteration event

Seawater-derived fluids

All the analysed samples (minerals and WR) have 87Sr86Sr(T) outside the domain of primary MORB magmasand variable Sr contents Individual minerals have Srcontents reflecting their different mineralliquid partitioncoefficients Minerals characterized by a very high affi-nity for Sr such as plagioclase (ie Sr mineralliquidpartition coefficients 1) have very high Sr contentsTherefore the high abundance of plagioclase in the sam-ples analysed is responsible for the high Sr content of thestudied whole rocks The Sr content of all the whole rocksis relatively homogeneous (Table 5) without clear distinc-tion between country-rock gabbros and dykes and veinsand ranges from 110 to 200 ppm except for the epidosite(4700 ppm) Reported on a 87Sr86Sr vs 1Sr diagram(Fig 10a) most whole rocks and plagioclases analysed arecharacterized by a 1Sr ratio lower than 001 and plot inthe left part of this diagram Compared with N-MORBthe studied massive and anatectic gabbros and their con-stituent plagioclases have similar to slightly higher Srcontents but substantially higher 87Sr86Sr ratios(Fig 10a) Considering Cretaceous seawater as a possiblehigh 87Sr86Sr mixing component [87Sr86Sr 07073at 90Ma after Burke et al (1982)] responsible for theobserved geochemical modifications exchanges cannothave occurred in a closed system as seawater has too lowa Sr content (ie 8 ppm de Villiers 1999) An open-system process allowing penetration of larger quantitiesof seawater can efficiently modify the Sr isotopic ratio ofthe rocks Alternately the fluids could also be seawaterthat was modified through exchange with the surround-ing rocks during its transit through the oceanic crustalsection This modified seawater would be more enrichedin Srwith a 87Sr86Sr ratio intermediate between unmodi-fied seawater and MORBMinerals devoid of late LT alteration imprints (parga-

site green hornblende and pyroxene) and characterizedby very low Sr contents plot on the right of the diagramclose to or on the mixing line between seawater andMORB (Fig 10a) The difference between these mineralsand the other samples (WR and plagioclases) is mainlydue to the Sr fractionation coefficients of these differentminerals and to the large quantity of plagioclase inthe studied rocks The process responsible for the


1202

modification of the Sr isotopic composition fromMORB-source value is however explained by the same phenom-enon As all these minerals display initial 87Sr86Sr ratiosdistinct from the MORB source and because they equili-brated at VHT or HT temperatures this supports anearly intervention of seawater during crystallization ofthese minerals Most of these samples with the exceptionof the epidosite dyke overlap the domains defined byKawahata et al (2001) for the Wadi Fizh gabbros alteredat VHT and HT conditions in the amphibolite facies(labelled lsquoVHTrsquo and lsquoHTrsquo in Fig 9a)Three samples (two epidosite dykes and an one epidote

fraction) have very high Sr contents and the highest Sr

isotopic compositions of the present dataset The twowhole-rock samples overlap the field of the Wadi Fizhsamples altered at high temperature during greenschist-facies metamorphism (Kawahata et al 2001) This typeof alteration is common at the ridge axis and formedthrough intensive exchange with seawater-derived fluidsFigure 10b indicates that all the Sr---O isotope data are

distinct from MORB compositions and suggests that thefluids reacting with the magmas could be derived fromseawater In addition the d18O values show that isotopicexchange occurred under VHT or HT conditions Thefluids could have the composition of seawater or theycould have the composition of seawater modified through

0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)

Fig 10 (a) Initial 87Sr86Sr isotopic ratios plotted against 1Sr for whole rocks and mineral separates from the gabbro section of the Omanophiolite Fields shown are from Kawahata et al (2001) and correspond to MT-----basalt sheeted dyke diabase altered at medium temperature(prehnite---actinolite facies sequence 3) HT-----diabase plagiogranite metagabbro and epidosite formed at high temperature (greenschist faciessequence 4) VHT-----gabbro altered at very high temperature (amphibolite facies sequence 5) The dashed line is a binary mixing line betweenMORB (Lanphere et al 1981) and Cretaceous seawater (Burke et al 1982) (b) Initial 87Sr86Sr isotopic composition plotted against d18O value forwhole rocks and minerals from the Oman ophiolite Cretaceous seawater and MORB end-members as in (a) Dashed line represents mixing curvebetweenMORB and seawater at high temperature (HT) Low-temperature (LT) exchanges between these two components would be responsible foran increase of the d18O primary MORB value


1203

exchange with the surrounding rocks during its penetra-tion into the crustal section In an environment in whichfluid---rock interaction occurs at variable temperaturesthe d18O is greatly influenced by the temperature atwhich the exchange took place and by the waterrockratio It is evident from Figs 9b and 10b that none of thestudied gabbros have plagioclase and amphibole withMORB-like d18O and 87Sr86Sr values The separateminerals display a broad range of d18O values and mostexhibit extreme 18O depletion (Table 5) Hydrothermalexchange kinetics are similar in amphibole and pyroxeneand these two minerals are more resistant to oxygenexchange during water---rock interaction than coexistingplagioclase (Gregory et al 1989) The most probableexplanation of the low d18O values measured in bothamphiboles and pyroxenes is that they crystallized athigh temperature in the presence of a relatively low 18Oseawater-derived hydrothermal fluid [d18O from 01 to07 after Gregory amp Taylor (1981)] The anomalouslyhigh d18O value (thorn1009) measured for the plagioclase ofthe micro-gabbroic dyke (01 OA19d) can be interpretedas resulting from a superimposed overprint caused by alate-stage penetration of fluids at lower temperature Inthis sample the occurrence of such different 18O16Oratios between coexisting plagioclase and amphibole isnot consistent with equilibrium fractionation betweenthese two minerals at any possible temperature Thisobservation suggests that parts of the ophiolite sequencehave undergone a high-temperature hydrothermal eventprior to the later low-temperature event that producedthe strong 18O increase in coexisting plagioclaseThe depletion of the d18O values results from high-temperature hydrothermal alteration (Gregory amp Taylor1981 Stakes amp Taylor 1992) The oxygen isotopic datasupport the contention that most studied samples havebeen affected by a VHT---HT hydrothermal alteration byfluids derived from seawater Some of the analysed sam-ples presenting petrological evidence of crystallization ofLT secondary minerals have been overprinted by the latelow-temperature alteration thus swamping the earlierhigh-temperature alteration effects

Determination of waterrock ratio

To better evaluate the exchange between seawater andthe gabbroic rocks waterrock ratios (WR) have beenestimated for the whole rocks analysed during the courseof this study The different models used to constrain thisratio mainly differ by the calculation of the effective ratioor by the estimated weight ratio and by considering openor closed systems for water circulation (Albareede et al1981 McCulloch et al 1981) The WR ratios reportedin Table 5 have been calculated assuming a closed sys-tem Using this formulation these values are minimabecause the calculation always uses pristine fluid for the

initial fluid thus maximizing the value in the denomina-tor If the fluid was shifted to lower 87Sr concentrations byexchange with the rock on the downward path theinferred values would be much higher (Davis et al 2003)The calculated WR ratios for the samples from this

study range from 31 to 219 (Table 5) Two main groupsof samples can be recognized on the basis of their waterrock ratios The lowest ratios ranging from 31 to 47have been determined for massive gabbros or anatecticgabbros but also for dykes and veins devoid of late LTalteration Similar ratios have been previously calculatedfor example for the discharged hydrothermal solutions atthe 13N and 21N East Pacific Rise (Di Donato et al1990 Fouquet et al 1991) The gabbros from the Ibrasection in the Oman ophiolite gave effective WR ratiosof 05 33 and 42 (McCulloch et al 1981) in goodagreement with the values obtained in this study Theleast altered gabbro of the Ibra section yields a WR ratioof 05 in good agreement with the exceptionally fresh-ness of this rock characterized by typical mantle oxygenvalues for its minerals (McCulloch et al 1981) Samplescharacterized by waterrock effective ratios in the rangeof 3---5 can be related to penetrative alteration via thehydrothermal system Lecuyer amp Reynard (1996) havedemonstrated in oceanic gabbros from the Hess Deepaltered in similar HT conditions that WR mass ratios inthe range of 02---1 are sufficient to account for the mod-ified stable isotope signature of the gabbros Higherwaterrock values (WR 45) have been calculated forsamples affected by superimposed late hydrothermalalteration and for the epidosite samples (Table 5) Theyprobably acquired their isotopic characteristics throughinteraction with a larger volume of seawater duringgreenschist-facies metamorphism Similar or higherWR values have been published in previous studies(ie McCulloch et al 1981 Kawahata et al 2001)They correspond either to samples from the upper-crus-tal sequence (ie basalt sheeted dyke or plagiogranite) orto gabbros from the crustal section located in a particularenvironment such as for example the Wadi Fizh sectionthat is located close to a segment boundary along thepalaeo-spreading axis (Nicolas et al 2000)

Mechanism for seawater interaction withmagma

Nicolas et al (2003) have proposed that variable amountsof seawater can circulate at high temperature through-out the crustal section down to the walls of the magmachamber via a network of parallel microcracks a fractionof a millimetre wide Such microcracks and their relation-ship with the VHT---HT hydrous alteration in the sur-rounding gabbros have been described in detail byNicolas et al Via this network of microcracks largeamounts of seawater can have reacted with the magma


1204

and induced variable changes of its Sr and O isotopiccomposition This regular network of parallel micro-cracks could constitute the recharge system and thehydrated gabbroic dykes the discharge system Physicalparameters and the geophysical models of Nicolas et al(2003) are in agreement with this scenario Such a pene-tration of seawater-derived hydrothermal fluids throughthe lower crust along grain boundaries and a microscopicfracture network at temperatures 4750C is consistentwith recent thermodynamic models (McCollom amp Shock1998)Seawater-altered and high-temperature recrystallized

diabases (protodykes) from the overlying sheeted dykecomplex stoped into the melt lenses could represent anindirect way for seawater to enter the system as they canremelt during their subsidence through the magmachamber A simple mass balance calculation suggeststhat this indirect contamination is not significant Assess-ments of the amount of recycled crust 1 in volumeby Nicolas et al (2000) based on the protodyke remnantsin the gabbro section or 20 by Coogan et al (2003)based on chlorine content in EPR basalts lead to a sea-waterrock ratio of the order of 104 to 103Thus following Nicolas et al (2003) we propose that

seawater has been introduced along microcracks down tothe walls of the magma chamber and has diffused alonggrain boundaries in the way described by Manning et al(2000) progressively invading the host gabbro Gabbroicdykes result from the injection of hydrous melt into thehost gabbros at falling temperatures as they drift awayfrom the magma chamber This water-saturated meltcould result from the extensive hydration of the crystal-lizing gabbros near the walls of the magma chamberwhen seawater penetrates through this wall (Fig 1)Similar plumbing systems driving seawater down to the

limit of the magma chamber and back to the surface havebeen already proposed in other environments such as theMid-Atlantic Ridge (Kelley amp Delaney 1987 Cooganet al 2001) the East Pacific Rise at Hess Deep (Gillis1995 Manning et al 1996a 1996b) the Tonga forearc(Banerjee amp Gillis 2001) and the Troodos ophiolite(Gillis amp Roberts 1999) The melting curve of wet basalthas a negative slope but is close to the dry solidus at lowpressure in the lower gabbros and the first melts areplagiogranitic (Spulber ampRutherford 1983) Such plagio-granites are ubiquitous in the highest gabbros and in theroot zone of sheeted dykes in Oman (Rothery 1983Juteau et al 1988 Nicolas amp Boudier 1991) in manyother ophiolites and in the oceanic crust where they havebeen interpreted as resulting either from wet anatexis ofhot gabbros or from the final product of crystallization ofa basaltic melt (Spulber amp Rutherford 1983) Plagio-granites are rare in the lower gabbros exceptionallyassociated with hydrous gabbro segregations inside thelayered gabbros Their constitutive minerals are also

remarkably absent along the VHTmicrocracks althoughthese gabbros were above the wet solidus A possibleexplanation has been proposed by McCollom amp Shock(1998) who wrote that at high temperature lsquoaqueousfluids may leave very little conspicuous petrological evid-ence for their presencersquo the reason being that thehigh-T conditions would be closer to batch meltingObviously more detailed studies on this specific problemare needed We conclude that the large degree of hydrousmelting locally required at the walls of the magma cham-ber to account for the generation of a gabbroic hydrousmelt may have erased the traces of the incipient plagio-granitic melt

CONCLUSIONS

Fostered by the recent discovery of high-temperatureseawater contamination in some gabbros of the Omanophiolite (Manning et al 2000) we have conducted astudy on 500 gabbro specimens from selected areas ofthe entire Samail ophiolite belt and on the hydrous gab-broic dykes that cross-cut them The highest-temperaturereactions (VHT) recorded in olivine and clinopyroxene ingabbros as orthopyroxene and pargasite coronas reach975C They are followed at lower HT conditions withreplacement of olivine by an assemblage of tremolitemagnetite and plagioclase surrounded by chlorite andby pargasite development in clinopyroxene followedfinally by the LT lizardite---olivine and saussurite---plagioclase greenschist-facies alteration With a fewexceptions the VHT alteration tends to be restricted tothe lower gabbros and to the vicinity of the Moho andthe HT alteration to the middle and upper gabbros Thepreservation of the vertical distribution of VHT---HTfacies indicates that progressive cooling during off-axisspreading did not obliterate this distribution and conse-quently that the VHT---HT hydrothermal alteration tookplace in a very restricted time interval at the limit of thecooling magma chamber In the deep and hot gabbrosthe main water channels may be sub-millimetre-sizedmicrocracks with a dominantly vertical attitude the ori-gin and dynamics of which have been investigated in aprevious paper (Nicolas et al 2003)Beyond these high-temperature alteration zones mas-

sively induced in the gabbros seawater may be respons-ible for the generation of clinopyroxene---pargasitegabbro dykes that cross-cut all gabbros and that areupsection clearly connected to the LT hydrothermalvein system Petrostructural evidence suggests that thesedykes were generated by hydration of the crystallizinggabbros near the internal wall of the LVZ---magmachamber The resultant melts were subsequently intrudedat various levels in the cooling lower and middle gabbrosPetrological observations of nearly all the gabbros ana-lysed in the present study located from the root zone of


1205

the sheeted dyke complex down to the Moho emphasizethe imprint of VHT---HT hydrous alteration The VHThydrothermal event is characterized by temperatures ofequilibration around 900---1000C The temperatures atwhich the HT hydrous event occurred are estimated tobe in the range 550---900CStrontium and oxygen isotope compositions measured

on whole rocks and separated minerals significantlydepart from primary MORB values The Sr and O iso-tope data obtained for pargasite green hornblende andclinopyroxene record the participation of seawater at thetemperature of crystallization of the minerals Plagio-clases and whole rocks define a trend toward a compo-nent characterized by a high radiogenic 87Sr86Sr valueand a higher Sr content than normal seawater Seawateris clearly identified as the fluid responsible for the modi-fication of the Sr and O signatures for both massivegabbros and dykes and veins Nevertheless the high Srcontent of the extraneous component requires eitheropen-system exchange allowing penetration of a greaterquantity of seawater or penetration of seawater modifiedby interaction with the oceanic crust during its travel paththrough the crustal section The waterrock ratio calcu-lated on the basis of the Sr isotopes is between three andfive for the enclosing gabbros and for the least LT altereddykes The VHT---HT hydrothermal event affectingthese samples is related to penetrative alteration via therecharge and discharge hydrothermal system Thewaterrock ratio is 10 for dykes exhibiting evidenceof a LT hydrothermal alteration overprint and reaches22 for the epidosite dyke The depletion in d18O char-acterizes all the studied samples with the single exceptionof the micro-gabbroic dyke plagioclase This agreeswith the conclusions based on Sr isotopes suggestingthat these samples have undergone exchange with sea-water-derived fluids during a VHT---HTalteration hydro-thermal event

ACKNOWLEDGEMENTS

This work has benefited from financial support by theCentre National de la Recherche Scientifique (INSUInteerieur-Terre andDYETI programmes) and inOmanfrom the willingness of the Directorate of MineralsMinistry of Commerce and Industry and the hospitabil-ity of the people Technical help in the laboratory is alsoacknowledged including C Nevado for the thin sectionsE Ball for the illustrations B Galland for her assistancein the chemistry room and C Bassoulet for help duringthermal ionization mass spectrometric analyses of the Srresults from the leaching experiments Constructivereviews from R T Gregory C Lecuyer an anonymousreviewer and particularly from M Wilson greatlyhelped to improve an earlier version of the manuscript

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phase relations between greenschist and amphibolite in a basaltic

system American Journal of Science 274 613---632

MacLeod C J amp Rothery D A (1992) Ridge axial segmentation in

the Oman ophiolite evidence from along-strike variations in the

sheeted dyke complex Geological Society of America Special Papers 60

39---63

Manning C E MacLeod C J amp Weston P E (1996a) Fracture-

controlled metamorphism of Hess Deep gabbros site 984

constraints on the roots of mid-ocean ridge hydrothermal systems

at fast-spreading centers In GillisM C Allan KM ampMeyer P S

(eds) Proceedings of the Ocean Drilling Program Scientific Results 147

College Station TX Ocean Drilling Program pp 189---211Manning C E Weston P E amp Mahon K I (1996b) Rapid high-

temperature metamorphism of East Pacific Rise gabbros from Hess

Deep Earth and Planetary Science Letters 144 123---132Manning C E MacLeod C J amp Weston P E (2000) Lower-crustal

cracking front at fast-spreading ridges evidence from the East Pacific

Rise and the Oman ophiolite Journal of the Geological Society London

349 261---272McCollom T M amp Shock E L (1998) Fluid---rock interactions in

the lower oceanic crust thermodynamic models of hydrothermal

alteration Journal of Geophysical Research 103 547---575

McCulloch M T Gregory R T Wasserburg G J amp Taylor H P

(1981) Sm---Nd Rb---Sr and 18O16O isotopic systematics in an

oceanic crustal section evidence from the Samail ophiolite Journal of

Geophysical Research 86(B4) 2721---2735Mevel C Gillis K M Allan J F amp Meyer P S (eds) (1996)

Proceedings of the Ocean Drilling Program Scientific Results 147 College

Station TX Ocean Drilling Program

Nehlig P amp Juteau T (1988) Flow porosities permeabilities and

preliminary data on fluid inclusions and fossil thermal gradients in

the crustal sequence of the Sumail ophiolite (Oman) Tectonophysics

151 199---221

Nehlig P Juteau T Bendel V amp Cotten J (1994) The root zone of

oceanic hydrothermal systems constraints from the Samail ophiolite

(Oman) Journal of Geophysical Research 99 4703---4713

Nicolas A amp Boudier F (1991) Rooting of the sheeted dyke complex

in Oman ophiolite In Peters Tj Nicolas A amp Coleman R (eds)

Ophiolite Genesis and Evolution of the Oceanic Lithosphere Dordrecht

Kluwer Academic pp 39---54


1207

Nicolas A amp Ildefonse B (1996) Flow mechanism and viscosity in

basaltic magma chambers Geophysical Research Letters 23(16)

2013---2016

Nicolas A Ceuleneer G Boudier F amp Misseri M (1988) Structural

mapping in the Oman ophiolites mantle diapirism along an ocean

ridge Tectonophysics 151 27---56

Nicolas A Boudier F Ildefonse B amp Ball E (2000) Accretion

of Oman and United Arab Emirates ophiolite-----discussion of a

new structural map Marine Geophysical Research 21(3---4)147---179

Nicolas A Boudier F Michibayashi K amp Gerbert-Gaillard L

(2001) Aswad massif (United Arab Emirates) archetype of the

Oman---UAE ophiolite belt Geological Society of America Bulletin 349

499---451

Nicolas A Mainprice D amp Boudier F (2003) High temperature

seawater circulation through the lower crust of ocean-ridges-----amodel derived from the Oman ophiolites Journal of Geophysical


2372

Pallister J S amp Hopson C A (1981) Samail ophiolite plutonic suite

field relations phase variation cryptic variation and layering and a

model of a spreading ridge magma chamber Journal of Geophysical

Research 86 2593---2644Phipps Morgan J amp Chen J Y (1993) Dependence of ridge-axis

morphology on magma supply and spreading rate Nature 364

706---708

Pin C Briot D Bassin C amp Poitrasson F (1994) Concomitant

extraction of Sr and Sm---Nd for isotopic analysis in silicate samples

based on specific extraction chromatography Analytica Chimica Acta

298 209---217

Rothery D A (1983) The base of a sheeted dyke complex Oman

ophiolite implications for magma chambers at oceanic spreading

axes Journal of the Geological Society London 140 287---296

Spear F S (1981) An experimental study of hornblende stability and

compositional variability in amphibolite American Journal of Science

281 697---734

Spulber S D amp Rutherford M J (1983) The origin of rhyolite and

plagiogranite in oceanic crust an experimental study Journal of

Petrology 24 1---25Stakes D S (1991) Oxygen and hydrogen isotope compositions of

oceanic plutonic rocks high-temperature deformation and meta-

morphism of oceanic layer 3 In Taylor H P OrsquoNeil J et al (eds)

Geochemical Society Special Publication 3 77---90

Stakes D S amp Taylor H P (1992) The northern Samail ophiolite an

oxygen isotope microprobe and field study Journal of Geophysical

Research 97(B5) 7043---7080Staudigel H Davies G R Hart S R Marchant M amp Smith B

M (1995) Large scale isotopic Sr Nd and O isotopic anatomy of

altered oceanic crust DSDPODP sites 417418 Earth and Planetary

Science Letters 130 169---185Turner F J amp Verhoogen J (1960) Igneous and Metamorphic Petrology

New York McGraw---Hill 694 pp

Wilcock W S D amp Delaney J R (1996) Mid-ocean ridge

sulfide deposits evidence for heat extraction from magma

chambers or cracking fronts Earth and Planetary Science Letters 145

49---64

Witt G amp Seck H A (1989) Origin of amphibole in recrystallized

and porphyroclastic mantle xenoliths from Rhenish massif implica-

tions for the nature of mantle metasomatism Earth and Planetary

Science Letters 91 327---340


1208

et al (2001) on the basis of a Sr isotope study of the crustalunit in the Fizh massif of northern Oman found a rise inthe temperature of hydrothermal alteration from lowgreenschist facies in the basalts to amphibolite-facies con-ditions in the gabbrosBoudier et al (2000) have also suggested that seawater

could contaminate the lower gabbros during their crystal-lization as recorded by the crystallization of gabbro-norites in place of olivine gabbros This contaminationat very high temperatures (VHT) possibly as high as1200C is restricted to those parts of the Oman palaeo-ridge that display evidence of ridge-related tectonic activ-ity and the seawater contamination was attributed to thisparticular tectonic setting

Improved seismological modelling of fast-spreadingridges at the East Pacific Rise axis at 9300N has sug-gested that there may be significant narrowing of thelow-velocity zone (LVZ) below the melt lens (Dunn et al2000) with respect to earlier models This narrowingwas explicitly ascribed by Dunn et al to the existence ofdeep high-T hydrothermal circulation at modern oceanicridges This raises the question of the definition of whatshould be considered as the magma chamber below amid-ocean ridge On the basis of extensive studies of theSamail ophiolite Nicolas et al (1988) have shown that themagma chamber was tent-shaped in three dimensionsextending to the base of the crust consistent with theshape of the LVZ found below modern ridges Hence the

Fig 1 (a) Simplified map of the Oman---UAE ophiolite including the inferred location of the palaeo-ridge axes and main shear zones [modifiedfrom Nicolas et al (2000)] (b) Simplified map of the Samail ophiolite Thin numbered lines represent the log-sections of Fig 4 along wadis wherealteration facies have been studied Bold lines are the wadi sections selected for detailed petrological and geochemical work in this study


1182







water in Sea Floor

Magma chamber

water out

gabbroicdike




750degC

500degC

1200degC


hydrothermal cracks

hydrothermal cracks

VHT

plastic mantle flow

maficdike

Moho

microgabbrodike

HT



1183






GABBRO SECTION


Alteration facies








1184



(a) (b)

(c) (d)

(e) (f)

olopx

kel

pl

ol

hbol

amcpx

cpx

hb

chl

am+pl+mt

idg

am

hb

pl

hb

ol

cpx

opx

mt

pl



1185





2 Km

3

4

5

6

7


High T

Very High T

0 High T

Upper Crust

LID

Lower Crust

MohoMTZ

DEPTH1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27


0

10

20

30

40

50

60

70

80

90

100

SD root

zone

upper

gabbros

middle

gabbros

lower

gabbros

MTZ

BHb-GHb CPX

Chl-Amph core OL

Chl-Amph rim OL

0

5

10

15

20

25

30

SD root

zone

upper

gabbros

middle

gabbros

lower

gabbros

MTZ

Opx OL

BHb OL

No VHTHT

Unaltered OL core

HT

VHT

(a)

(b)

Plst def

gabbros



1186







(b) (c)(a)

(d) (e)

thulite

pistacite

white microvein

white vein

green vein

green vein

gabbroic dike

epidote vein

gabbroic dike



1187





(a) (b) (c)

g(e)(d)


hwhite vein

hblpl

pcpx


eediabasedikdike







1188







O---Sr isotopes







1189


Oxygen isotopes


RESULTS











1190




Sam

ple

nam

eSite

Locationin

gab

broic

section

Typ

eofrock

Distance

to

Moho(km)

Parag

enesis

Alteration

87Sr

86Srinitial1

d18O

()2

94MA2

Maq

sad

From

MTZ

Layered

gab

bro

0Olivine(M

gno74---75)3

OPXco

ronas

(Mgno78---79)

WRfrac14

070322

WRfrac14

thorn495

CPX

Palegreen

Am

(cumact)

CPXfrac14

070324

nd

Plagioclase(A


Nolow-T

alteration

Plfrac14

070322

Plfrac14

thorn479

Solidfluid

inclusionsin

Pl

97OA128b

Wad

iWaryiah

From

lower

gab

bro

Layered

gab

bro

1CPX

Low-T

alteration

WRfrac14

070333

nd

Plagioclase(A

n85---87)

Prehnitemicroveins

CPXfrac14

070422

CPXfrac14

thorn523

Plfrac14

070328

Plfrac14

thorn414

01OA41d2

Wad

iGideah

From

upper

gab

bro

Gab

bro

patch

in

laminated

gab

bro

36

CPXrecrystallized


(An57---87)norm

alzoning

Black

pargasitic

honblende

WRfrac14

070351

CPXfrac14

070378

Plfrac14

070426

WRfrac14

thorn480

nd

Plfrac14

thorn504

Hbdfrac14

070355

nd

01OA19aamp

dWad

iWaryiah

Inlayeredgab

bro

Gab

broic

dyke

01

Olivine

OPXpoikilitic

WRfrac14

070341

WRfrac14

thorn567

CPX

Black

pargasite

Hbdfrac14

070324

Hbdfrac14

thorn287

Plagioclase(A

n73---95)


Plfrac14

nd

Plfrac14

thorn10 09

Hem

atite

WRfrac14

070418

nd

Green

Mg-hornblende

Acthornblende

Epidote

02OA90b

Wad

iAl-Abyad

Inlayeredgab

bro

Dioriticdyke

015

Green

Mg-hornblende

Hbdfrac14

070427

Hbdfrac14

thorn239

Plagioclase(A

n83---87)

Plfrac14

070387

Plfrac14

thorn498

Solidfluid

inclusionsin

plagioclase

01OA15f

Wad

iWaryiah

Inlayeredgab

bro

Comb-textured

gab

broic

dyke

025

CPXidiomorphic

Plagioclase(A

n95---99)norm

alzoning

BrownMg-H

ornblende

WRfrac14

070458

nd

02OA43a

Wad

iMayah

Inlayeredgab

bro

vein

Green

amphibole

1Palegreen


Plagioclase(A

n91---97)in

reactionmargin

Hbdfrac14

070431

Hbdfrac14

thorn310

01OA36b

Wad

iGideah

Inlayeredgab

bro

epidosite

dyke

25

CPX

Epidote

WRfrac14

070519

nd

Plagioclase

Epfrac14

070554

nd

CPXclinopyroxene

Plplagioclase

OPXorthopyroxene

Amam

phibolecu

mcu

mmingtonite

actactinolite


Epep

idotend

notdetermined

187Sr


95Ma(H

acker1994)Errors


inTab

le4

2Analyticalerrors

oftheoxygen

isotopevalues

are02

(2s)

3Mgnumber


Fe)

4Percentageofan

orthitein

plagioclase


1191







Blundy (1994)


rim core rim core

01 OA41d2 878 953 ------- -------

01 OA19a 935 974 825 869

01 OA19d 890 933 789 -------

02 OA37b ------- ------- 816 849

02 OA90b ------- ------- 859 833


1192










(wt )



gabb dyke


(margin)

SiO2 4830 4815 4749 4524 4339 4799 389 4371

Al2O3 2785 2032 2438 1474 1246 1192 2752 1646

Fe2O3 328 266 404 981 1204 592 381 623

MnO 003 004 005 014 016 006 008 014

MgO 405 737 427 1031 1686 1326 187 739

CaO 1289 1908 1477 1235 1156 166 2471 2339

Na2O 292 123 257 258 111 075 000 013

K2O 000 000 009 006 000 000 000 000

TiO2 005 017 063 230 064 086 013 042

P2O5 008 007 013 018 009 013 007 010

LOI 033 076 138 216 161 237 274 190

Total 9978 9985 998 9987 9992 9986 9983 9987



1193


aofselectedam

phibolespaired


Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

01OA19a

Mg-hornblende

core

45 60

26

10 78

009

860

015

16 56

12 00

212

007

96 72

6552

1448

0366

0083

0552

0004

3409

0594

0016

0611

0018

1843

0903

899

Mg-hornblende

core

47 99

263

850

002

897

011

16 61

12 10

160

020

96 36

6894

1106

0334

0028

0483

0002

3557

0594

0014

0446

0036

1862

0892

834

Mg-hornblende

rim

51 17

247

596

001

761

014

18 11

12 19

103

010

96 47

7257

0743

0253

0016

0414

0001

3828

0488

0016

0284

0018

1853

0894

820

Mg-hornblende

rim

47 50

291

920

004

880

014

16 46

11 95

174

008

96 07

6835

1165

0396

0015

0506

0005

3529

0552

0017

0486

0015

1843

0887

825

Mg-hornblende

rim

49 57

269

742

000

799

017

18 07

12 02

133

014

96 88

7013

0987

0261

0018

0575

0000

3811

0371

0020

0365

0026

1821

0860

831

Mg-hornblende

core

47 83

181

872

003

840

011

14 48

12 18

159

008

93 59

6814

1186

0279

0018

0644

0004

3711

0357

0013

0438

0015

1859

0907

874

Pargasite

rim

42 15

249

11 87

024

10 07

013

13 84

11 43

263

032

96 61

6188

1812

0242

0434

0299

0028

3028

0937

0016

0749

0059

1797

0804

972

Pargasite

rim

42 22

260

11 86

026

10 21

011

13 71

11 48

253

032

96 59

6201

1799

0254

0429

0299

0030

3001

0955

0014

0720

0060

1807

0803

962

Pargasite

core

42 05

263

11 45

030

10 19

011

13 80

11 47

246

032

96 46

6189

1811

0175

0478

0299

0035

3029

0956

0014

0702

0060

1809

0767

974

Pargasite

rim

42 36

247

11 90

016

945

013

14 16

11 76

249

026

95 98

6239

1761

0305

0366

0276

0019

3109

0888

0016

0710

0049

1856

0818

926

Pargasite

core

42 50

291

11 64

016

984

015

14 22

11 41

256

034

96 69

6219

1781

0227

0426

0322

0018

3103

0883

0018

0727

0063

1789

0812

974

Pargasite

rim

42 76

270

12 03

017

920

012

14 87

11 82

244

025

96 73

6224

1776

0880

0335

0368

0020

3226

0752

0015

0689

0047

1843

0841

941

Pargasite

rim

42 13

181

13 54

016

921

009

12 77

12 13

254

032

96 98

6172

1828

0510

0450

0000

0018

2788

1129

0011

0721

0059

1905

0841

874

01OA19d

Mg-hornblende

49 26

047

624

011

11 46

017

15 39

12 21

108

009

96 48

7137

0863

0202

0051

0437

0013

3323

0951

0021

0302

0018

1896

0768

771

Mg-hornblende

46 03

287

932

018

906

017

14 77

12 87

193

007

97 28

6672

1328

0265

0313

0046

0021

3191

1053

0021

0542

0012

1999

0758

808

Pargasite

41 89

429

11 65

008

11 03

017

13 52

11 37

259

017

96 77

6159

1841

0179

0474

0345

0010

2963

1012

0021

0739

0032

1791

0770

975

Pargasite

rim

42 80

340

11 16

009

11 01

018

13 73

11 67

240

022

96 67

6293

1707

0226

0376

0322

0010

3009

1032

0022

0684

0041

1839

0605

880

Pargasite

core

42 58

351

11 27

006

11 63

018

13 51

11 46

239

022

96 82

6257

1743

0209

0387

0391

0007

2959

1039

0023

0680

0042

1804

0595

893

Pargasite

rim

42 14

393

11 28

006

11 71

014

13 35

11 33

235

033

96 62

6214

1786

0174

0435

0391

0007

2935

1054

0018

0673

0062

1790

0519

901

Pargasite

core

41 56

420

12 05

006

11 57

016

12 51

11 35

249

027

96 24

6168

1832

0277

0469

0276

0007

2768

1160

0021

0718

0052

1805

0537

882

Pargasite

core

41 33

438

11 49

008

11 66

015

13 35

11 45

264

026

96 80

6105

1894

0107

0487

0368

0009

2941

1073

0019

0757

0048

1813

0537

942

Pargasite

41 08

446

12 39

012

11 35

017

13 13

11 36

263

015

96 85

6049

1951

0199

0494

0368

0014

2882

1030

0021

0752

0027

1792

0758

975

02OA37b

Mg-hornblende

rim

45 15

260

984

002

13 28

019

14 01

10 87

128

009

97 33

6527

1473

0203

0283

0690

0002

3018

0915

0023

0360

0016

1683

0562

828

Mg-hornblende

rim

44 72

263

988

004

13 23

021

14 01

10 78

133

009

96 92

6494

1506

0185

0287

0713

0005

3032

0894

0025

0374

0018

1677

0593

854

Mg-hornblende

rim

45 68

247

935

004

12 87

020

14 10

11 00

121

011

97 02

6621

1379

0218

0269

0598

0004

3045

0962

0024

0341

0020

1708

0562

815

Mg-hornblende

core

43 94

291

10 87

001

12 60

023

13 73

10 59

142

011

96 39

6410

1590

0278

0319

0644

0001

2985

0893

0028

0401

0021

1655

0710

860

Mg-hornblende

core

44 62

270

10 37

001

12 66

019

14 12

10 58

140

008

96 73

6479

1521

0253

0294

0644

0001

3057

0893

0023

0395

0014

1646

0674

851

Mg-hornblende

rim

47 79

181

796

002

12 09

025

15 22

11 09

100

009

97 33

6866

1134

0214

0196

0506

0002

3260

0947

0030

0280

0016

1706

0503

767

Mg-hornblende

core

45 43

249

10 3

000

11 99

022

14 50

11 14

133

008

97 48

6524

1476

0267

0269

0644

0000

3103

0796

0027

0370

0015

1715

0703

838


1194

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein


alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam


Blundythermometer

(1994)Errors

are40

C


1195






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208







water in Sea Floor

Magma chamber

water out

gabbroicdike




750degC

500degC

1200degC


hydrothermal cracks

hydrothermal cracks

VHT

plastic mantle flow

maficdike

Moho

microgabbrodike

HT



1183






GABBRO SECTION


Alteration facies








1184



(a) (b)

(c) (d)

(e) (f)

olopx

kel

pl

ol

hbol

amcpx

cpx

hb

chl

am+pl+mt

idg

am

hb

pl

hb

ol

cpx

opx

mt

pl



1185





2 Km

3

4

5

6

7


High T

Very High T

0 High T

Upper Crust

LID

Lower Crust

MohoMTZ

DEPTH1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27


0

10

20

30

40

50

60

70

80

90

100

SD root

zone

upper

gabbros

middle

gabbros

lower

gabbros

MTZ

BHb-GHb CPX

Chl-Amph core OL

Chl-Amph rim OL

0

5

10

15

20

25

30

SD root

zone

upper

gabbros

middle

gabbros

lower

gabbros

MTZ

Opx OL

BHb OL

No VHTHT

Unaltered OL core

HT

VHT

(a)

(b)

Plst def

gabbros



1186







(b) (c)(a)

(d) (e)

thulite

pistacite

white microvein

white vein

green vein

green vein

gabbroic dike

epidote vein

gabbroic dike



1187





(a) (b) (c)

g(e)(d)


hwhite vein

hblpl

pcpx


eediabasedikdike







1188







O---Sr isotopes







1189


Oxygen isotopes


RESULTS











1190




Sam

ple

nam

eSite

Locationin

gab

broic

section

Typ

eofrock

Distance

to

Moho(km)

Parag

enesis

Alteration

87Sr

86Srinitial1

d18O

()2

94MA2

Maq

sad

From

MTZ

Layered

gab

bro

0Olivine(M

gno74---75)3

OPXco

ronas

(Mgno78---79)

WRfrac14

070322

WRfrac14

thorn495

CPX

Palegreen

Am

(cumact)

CPXfrac14

070324

nd

Plagioclase(A


Nolow-T

alteration

Plfrac14

070322

Plfrac14

thorn479

Solidfluid

inclusionsin

Pl

97OA128b

Wad

iWaryiah

From

lower

gab

bro

Layered

gab

bro

1CPX

Low-T

alteration

WRfrac14

070333

nd

Plagioclase(A

n85---87)

Prehnitemicroveins

CPXfrac14

070422

CPXfrac14

thorn523

Plfrac14

070328

Plfrac14

thorn414

01OA41d2

Wad

iGideah

From

upper

gab

bro

Gab

bro

patch

in

laminated

gab

bro

36

CPXrecrystallized


(An57---87)norm

alzoning

Black

pargasitic

honblende

WRfrac14

070351

CPXfrac14

070378

Plfrac14

070426

WRfrac14

thorn480

nd

Plfrac14

thorn504

Hbdfrac14

070355

nd

01OA19aamp

dWad

iWaryiah

Inlayeredgab

bro

Gab

broic

dyke

01

Olivine

OPXpoikilitic

WRfrac14

070341

WRfrac14

thorn567

CPX

Black

pargasite

Hbdfrac14

070324

Hbdfrac14

thorn287

Plagioclase(A

n73---95)


Plfrac14

nd

Plfrac14

thorn10 09

Hem

atite

WRfrac14

070418

nd

Green

Mg-hornblende

Acthornblende

Epidote

02OA90b

Wad

iAl-Abyad

Inlayeredgab

bro

Dioriticdyke

015

Green

Mg-hornblende

Hbdfrac14

070427

Hbdfrac14

thorn239

Plagioclase(A

n83---87)

Plfrac14

070387

Plfrac14

thorn498

Solidfluid

inclusionsin

plagioclase

01OA15f

Wad

iWaryiah

Inlayeredgab

bro

Comb-textured

gab

broic

dyke

025

CPXidiomorphic

Plagioclase(A

n95---99)norm

alzoning

BrownMg-H

ornblende

WRfrac14

070458

nd

02OA43a

Wad

iMayah

Inlayeredgab

bro

vein

Green

amphibole

1Palegreen


Plagioclase(A

n91---97)in

reactionmargin

Hbdfrac14

070431

Hbdfrac14

thorn310

01OA36b

Wad

iGideah

Inlayeredgab

bro

epidosite

dyke

25

CPX

Epidote

WRfrac14

070519

nd

Plagioclase

Epfrac14

070554

nd

CPXclinopyroxene

Plplagioclase

OPXorthopyroxene

Amam

phibolecu

mcu

mmingtonite

actactinolite


Epep

idotend

notdetermined

187Sr


95Ma(H

acker1994)Errors


inTab

le4

2Analyticalerrors

oftheoxygen

isotopevalues

are02

(2s)

3Mgnumber


Fe)

4Percentageofan

orthitein

plagioclase


1191







Blundy (1994)


rim core rim core

01 OA41d2 878 953 ------- -------

01 OA19a 935 974 825 869

01 OA19d 890 933 789 -------

02 OA37b ------- ------- 816 849

02 OA90b ------- ------- 859 833


1192










(wt )



gabb dyke


(margin)

SiO2 4830 4815 4749 4524 4339 4799 389 4371

Al2O3 2785 2032 2438 1474 1246 1192 2752 1646

Fe2O3 328 266 404 981 1204 592 381 623

MnO 003 004 005 014 016 006 008 014

MgO 405 737 427 1031 1686 1326 187 739

CaO 1289 1908 1477 1235 1156 166 2471 2339

Na2O 292 123 257 258 111 075 000 013

K2O 000 000 009 006 000 000 000 000

TiO2 005 017 063 230 064 086 013 042

P2O5 008 007 013 018 009 013 007 010

LOI 033 076 138 216 161 237 274 190

Total 9978 9985 998 9987 9992 9986 9983 9987



1193


aofselectedam

phibolespaired


Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

01OA19a

Mg-hornblende

core

45 60

26

10 78

009

860

015

16 56

12 00

212

007

96 72

6552

1448

0366

0083

0552

0004

3409

0594

0016

0611

0018

1843

0903

899

Mg-hornblende

core

47 99

263

850

002

897

011

16 61

12 10

160

020

96 36

6894

1106

0334

0028

0483

0002

3557

0594

0014

0446

0036

1862

0892

834

Mg-hornblende

rim

51 17

247

596

001

761

014

18 11

12 19

103

010

96 47

7257

0743

0253

0016

0414

0001

3828

0488

0016

0284

0018

1853

0894

820

Mg-hornblende

rim

47 50

291

920

004

880

014

16 46

11 95

174

008

96 07

6835

1165

0396

0015

0506

0005

3529

0552

0017

0486

0015

1843

0887

825

Mg-hornblende

rim

49 57

269

742

000

799

017

18 07

12 02

133

014

96 88

7013

0987

0261

0018

0575

0000

3811

0371

0020

0365

0026

1821

0860

831

Mg-hornblende

core

47 83

181

872

003

840

011

14 48

12 18

159

008

93 59

6814

1186

0279

0018

0644

0004

3711

0357

0013

0438

0015

1859

0907

874

Pargasite

rim

42 15

249

11 87

024

10 07

013

13 84

11 43

263

032

96 61

6188

1812

0242

0434

0299

0028

3028

0937

0016

0749

0059

1797

0804

972

Pargasite

rim

42 22

260

11 86

026

10 21

011

13 71

11 48

253

032

96 59

6201

1799

0254

0429

0299

0030

3001

0955

0014

0720

0060

1807

0803

962

Pargasite

core

42 05

263

11 45

030

10 19

011

13 80

11 47

246

032

96 46

6189

1811

0175

0478

0299

0035

3029

0956

0014

0702

0060

1809

0767

974

Pargasite

rim

42 36

247

11 90

016

945

013

14 16

11 76

249

026

95 98

6239

1761

0305

0366

0276

0019

3109

0888

0016

0710

0049

1856

0818

926

Pargasite

core

42 50

291

11 64

016

984

015

14 22

11 41

256

034

96 69

6219

1781

0227

0426

0322

0018

3103

0883

0018

0727

0063

1789

0812

974

Pargasite

rim

42 76

270

12 03

017

920

012

14 87

11 82

244

025

96 73

6224

1776

0880

0335

0368

0020

3226

0752

0015

0689

0047

1843

0841

941

Pargasite

rim

42 13

181

13 54

016

921

009

12 77

12 13

254

032

96 98

6172

1828

0510

0450

0000

0018

2788

1129

0011

0721

0059

1905

0841

874

01OA19d

Mg-hornblende

49 26

047

624

011

11 46

017

15 39

12 21

108

009

96 48

7137

0863

0202

0051

0437

0013

3323

0951

0021

0302

0018

1896

0768

771

Mg-hornblende

46 03

287

932

018

906

017

14 77

12 87

193

007

97 28

6672

1328

0265

0313

0046

0021

3191

1053

0021

0542

0012

1999

0758

808

Pargasite

41 89

429

11 65

008

11 03

017

13 52

11 37

259

017

96 77

6159

1841

0179

0474

0345

0010

2963

1012

0021

0739

0032

1791

0770

975

Pargasite

rim

42 80

340

11 16

009

11 01

018

13 73

11 67

240

022

96 67

6293

1707

0226

0376

0322

0010

3009

1032

0022

0684

0041

1839

0605

880

Pargasite

core

42 58

351

11 27

006

11 63

018

13 51

11 46

239

022

96 82

6257

1743

0209

0387

0391

0007

2959

1039

0023

0680

0042

1804

0595

893

Pargasite

rim

42 14

393

11 28

006

11 71

014

13 35

11 33

235

033

96 62

6214

1786

0174

0435

0391

0007

2935

1054

0018

0673

0062

1790

0519

901

Pargasite

core

41 56

420

12 05

006

11 57

016

12 51

11 35

249

027

96 24

6168

1832

0277

0469

0276

0007

2768

1160

0021

0718

0052

1805

0537

882

Pargasite

core

41 33

438

11 49

008

11 66

015

13 35

11 45

264

026

96 80

6105

1894

0107

0487

0368

0009

2941

1073

0019

0757

0048

1813

0537

942

Pargasite

41 08

446

12 39

012

11 35

017

13 13

11 36

263

015

96 85

6049

1951

0199

0494

0368

0014

2882

1030

0021

0752

0027

1792

0758

975

02OA37b

Mg-hornblende

rim

45 15

260

984

002

13 28

019

14 01

10 87

128

009

97 33

6527

1473

0203

0283

0690

0002

3018

0915

0023

0360

0016

1683

0562

828

Mg-hornblende

rim

44 72

263

988

004

13 23

021

14 01

10 78

133

009

96 92

6494

1506

0185

0287

0713

0005

3032

0894

0025

0374

0018

1677

0593

854

Mg-hornblende

rim

45 68

247

935

004

12 87

020

14 10

11 00

121

011

97 02

6621

1379

0218

0269

0598

0004

3045

0962

0024

0341

0020

1708

0562

815

Mg-hornblende

core

43 94

291

10 87

001

12 60

023

13 73

10 59

142

011

96 39

6410

1590

0278

0319

0644

0001

2985

0893

0028

0401

0021

1655

0710

860

Mg-hornblende

core

44 62

270

10 37

001

12 66

019

14 12

10 58

140

008

96 73

6479

1521

0253

0294

0644

0001

3057

0893

0023

0395

0014

1646

0674

851

Mg-hornblende

rim

47 79

181

796

002

12 09

025

15 22

11 09

100

009

97 33

6866

1134

0214

0196

0506

0002

3260

0947

0030

0280

0016

1706

0503

767

Mg-hornblende

core

45 43

249

10 3

000

11 99

022

14 50

11 14

133

008

97 48

6524

1476

0267

0269

0644

0000

3103

0796

0027

0370

0015

1715

0703

838


1194

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein


alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam


Blundythermometer

(1994)Errors

are40

C


1195






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208






GABBRO SECTION


Alteration facies








1184



(a) (b)

(c) (d)

(e) (f)

olopx

kel

pl

ol

hbol

amcpx

cpx

hb

chl

am+pl+mt

idg

am

hb

pl

hb

ol

cpx

opx

mt

pl



1185





2 Km

3

4

5

6

7


High T

Very High T

0 High T

Upper Crust

LID

Lower Crust

MohoMTZ

DEPTH1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27


0

10

20

30

40

50

60

70

80

90

100

SD root

zone

upper

gabbros

middle

gabbros

lower

gabbros

MTZ

BHb-GHb CPX

Chl-Amph core OL

Chl-Amph rim OL

0

5

10

15

20

25

30

SD root

zone

upper

gabbros

middle

gabbros

lower

gabbros

MTZ

Opx OL

BHb OL

No VHTHT

Unaltered OL core

HT

VHT

(a)

(b)

Plst def

gabbros



1186







(b) (c)(a)

(d) (e)

thulite

pistacite

white microvein

white vein

green vein

green vein

gabbroic dike

epidote vein

gabbroic dike



1187





(a) (b) (c)

g(e)(d)


hwhite vein

hblpl

pcpx


eediabasedikdike







1188







O---Sr isotopes







1189


Oxygen isotopes


RESULTS











1190




Sam

ple

nam

eSite

Locationin

gab

broic

section

Typ

eofrock

Distance

to

Moho(km)

Parag

enesis

Alteration

87Sr

86Srinitial1

d18O

()2

94MA2

Maq

sad

From

MTZ

Layered

gab

bro

0Olivine(M

gno74---75)3

OPXco

ronas

(Mgno78---79)

WRfrac14

070322

WRfrac14

thorn495

CPX

Palegreen

Am

(cumact)

CPXfrac14

070324

nd

Plagioclase(A


Nolow-T

alteration

Plfrac14

070322

Plfrac14

thorn479

Solidfluid

inclusionsin

Pl

97OA128b

Wad

iWaryiah

From

lower

gab

bro

Layered

gab

bro

1CPX

Low-T

alteration

WRfrac14

070333

nd

Plagioclase(A

n85---87)

Prehnitemicroveins

CPXfrac14

070422

CPXfrac14

thorn523

Plfrac14

070328

Plfrac14

thorn414

01OA41d2

Wad

iGideah

From

upper

gab

bro

Gab

bro

patch

in

laminated

gab

bro

36

CPXrecrystallized


(An57---87)norm

alzoning

Black

pargasitic

honblende

WRfrac14

070351

CPXfrac14

070378

Plfrac14

070426

WRfrac14

thorn480

nd

Plfrac14

thorn504

Hbdfrac14

070355

nd

01OA19aamp

dWad

iWaryiah

Inlayeredgab

bro

Gab

broic

dyke

01

Olivine

OPXpoikilitic

WRfrac14

070341

WRfrac14

thorn567

CPX

Black

pargasite

Hbdfrac14

070324

Hbdfrac14

thorn287

Plagioclase(A

n73---95)


Plfrac14

nd

Plfrac14

thorn10 09

Hem

atite

WRfrac14

070418

nd

Green

Mg-hornblende

Acthornblende

Epidote

02OA90b

Wad

iAl-Abyad

Inlayeredgab

bro

Dioriticdyke

015

Green

Mg-hornblende

Hbdfrac14

070427

Hbdfrac14

thorn239

Plagioclase(A

n83---87)

Plfrac14

070387

Plfrac14

thorn498

Solidfluid

inclusionsin

plagioclase

01OA15f

Wad

iWaryiah

Inlayeredgab

bro

Comb-textured

gab

broic

dyke

025

CPXidiomorphic

Plagioclase(A

n95---99)norm

alzoning

BrownMg-H

ornblende

WRfrac14

070458

nd

02OA43a

Wad

iMayah

Inlayeredgab

bro

vein

Green

amphibole

1Palegreen


Plagioclase(A

n91---97)in

reactionmargin

Hbdfrac14

070431

Hbdfrac14

thorn310

01OA36b

Wad

iGideah

Inlayeredgab

bro

epidosite

dyke

25

CPX

Epidote

WRfrac14

070519

nd

Plagioclase

Epfrac14

070554

nd

CPXclinopyroxene

Plplagioclase

OPXorthopyroxene

Amam

phibolecu

mcu

mmingtonite

actactinolite


Epep

idotend

notdetermined

187Sr


95Ma(H

acker1994)Errors


inTab

le4

2Analyticalerrors

oftheoxygen

isotopevalues

are02

(2s)

3Mgnumber


Fe)

4Percentageofan

orthitein

plagioclase


1191







Blundy (1994)


rim core rim core

01 OA41d2 878 953 ------- -------

01 OA19a 935 974 825 869

01 OA19d 890 933 789 -------

02 OA37b ------- ------- 816 849

02 OA90b ------- ------- 859 833


1192










(wt )



gabb dyke


(margin)

SiO2 4830 4815 4749 4524 4339 4799 389 4371

Al2O3 2785 2032 2438 1474 1246 1192 2752 1646

Fe2O3 328 266 404 981 1204 592 381 623

MnO 003 004 005 014 016 006 008 014

MgO 405 737 427 1031 1686 1326 187 739

CaO 1289 1908 1477 1235 1156 166 2471 2339

Na2O 292 123 257 258 111 075 000 013

K2O 000 000 009 006 000 000 000 000

TiO2 005 017 063 230 064 086 013 042

P2O5 008 007 013 018 009 013 007 010

LOI 033 076 138 216 161 237 274 190

Total 9978 9985 998 9987 9992 9986 9983 9987



1193


aofselectedam

phibolespaired


Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

01OA19a

Mg-hornblende

core

45 60

26

10 78

009

860

015

16 56

12 00

212

007

96 72

6552

1448

0366

0083

0552

0004

3409

0594

0016

0611

0018

1843

0903

899

Mg-hornblende

core

47 99

263

850

002

897

011

16 61

12 10

160

020

96 36

6894

1106

0334

0028

0483

0002

3557

0594

0014

0446

0036

1862

0892

834

Mg-hornblende

rim

51 17

247

596

001

761

014

18 11

12 19

103

010

96 47

7257

0743

0253

0016

0414

0001

3828

0488

0016

0284

0018

1853

0894

820

Mg-hornblende

rim

47 50

291

920

004

880

014

16 46

11 95

174

008

96 07

6835

1165

0396

0015

0506

0005

3529

0552

0017

0486

0015

1843

0887

825

Mg-hornblende

rim

49 57

269

742

000

799

017

18 07

12 02

133

014

96 88

7013

0987

0261

0018

0575

0000

3811

0371

0020

0365

0026

1821

0860

831

Mg-hornblende

core

47 83

181

872

003

840

011

14 48

12 18

159

008

93 59

6814

1186

0279

0018

0644

0004

3711

0357

0013

0438

0015

1859

0907

874

Pargasite

rim

42 15

249

11 87

024

10 07

013

13 84

11 43

263

032

96 61

6188

1812

0242

0434

0299

0028

3028

0937

0016

0749

0059

1797

0804

972

Pargasite

rim

42 22

260

11 86

026

10 21

011

13 71

11 48

253

032

96 59

6201

1799

0254

0429

0299

0030

3001

0955

0014

0720

0060

1807

0803

962

Pargasite

core

42 05

263

11 45

030

10 19

011

13 80

11 47

246

032

96 46

6189

1811

0175

0478

0299

0035

3029

0956

0014

0702

0060

1809

0767

974

Pargasite

rim

42 36

247

11 90

016

945

013

14 16

11 76

249

026

95 98

6239

1761

0305

0366

0276

0019

3109

0888

0016

0710

0049

1856

0818

926

Pargasite

core

42 50

291

11 64

016

984

015

14 22

11 41

256

034

96 69

6219

1781

0227

0426

0322

0018

3103

0883

0018

0727

0063

1789

0812

974

Pargasite

rim

42 76

270

12 03

017

920

012

14 87

11 82

244

025

96 73

6224

1776

0880

0335

0368

0020

3226

0752

0015

0689

0047

1843

0841

941

Pargasite

rim

42 13

181

13 54

016

921

009

12 77

12 13

254

032

96 98

6172

1828

0510

0450

0000

0018

2788

1129

0011

0721

0059

1905

0841

874

01OA19d

Mg-hornblende

49 26

047

624

011

11 46

017

15 39

12 21

108

009

96 48

7137

0863

0202

0051

0437

0013

3323

0951

0021

0302

0018

1896

0768

771

Mg-hornblende

46 03

287

932

018

906

017

14 77

12 87

193

007

97 28

6672

1328

0265

0313

0046

0021

3191

1053

0021

0542

0012

1999

0758

808

Pargasite

41 89

429

11 65

008

11 03

017

13 52

11 37

259

017

96 77

6159

1841

0179

0474

0345

0010

2963

1012

0021

0739

0032

1791

0770

975

Pargasite

rim

42 80

340

11 16

009

11 01

018

13 73

11 67

240

022

96 67

6293

1707

0226

0376

0322

0010

3009

1032

0022

0684

0041

1839

0605

880

Pargasite

core

42 58

351

11 27

006

11 63

018

13 51

11 46

239

022

96 82

6257

1743

0209

0387

0391

0007

2959

1039

0023

0680

0042

1804

0595

893

Pargasite

rim

42 14

393

11 28

006

11 71

014

13 35

11 33

235

033

96 62

6214

1786

0174

0435

0391

0007

2935

1054

0018

0673

0062

1790

0519

901

Pargasite

core

41 56

420

12 05

006

11 57

016

12 51

11 35

249

027

96 24

6168

1832

0277

0469

0276

0007

2768

1160

0021

0718

0052

1805

0537

882

Pargasite

core

41 33

438

11 49

008

11 66

015

13 35

11 45

264

026

96 80

6105

1894

0107

0487

0368

0009

2941

1073

0019

0757

0048

1813

0537

942

Pargasite

41 08

446

12 39

012

11 35

017

13 13

11 36

263

015

96 85

6049

1951

0199

0494

0368

0014

2882

1030

0021

0752

0027

1792

0758

975

02OA37b

Mg-hornblende

rim

45 15

260

984

002

13 28

019

14 01

10 87

128

009

97 33

6527

1473

0203

0283

0690

0002

3018

0915

0023

0360

0016

1683

0562

828

Mg-hornblende

rim

44 72

263

988

004

13 23

021

14 01

10 78

133

009

96 92

6494

1506

0185

0287

0713

0005

3032

0894

0025

0374

0018

1677

0593

854

Mg-hornblende

rim

45 68

247

935

004

12 87

020

14 10

11 00

121

011

97 02

6621

1379

0218

0269

0598

0004

3045

0962

0024

0341

0020

1708

0562

815

Mg-hornblende

core

43 94

291

10 87

001

12 60

023

13 73

10 59

142

011

96 39

6410

1590

0278

0319

0644

0001

2985

0893

0028

0401

0021

1655

0710

860

Mg-hornblende

core

44 62

270

10 37

001

12 66

019

14 12

10 58

140

008

96 73

6479

1521

0253

0294

0644

0001

3057

0893

0023

0395

0014

1646

0674

851

Mg-hornblende

rim

47 79

181

796

002

12 09

025

15 22

11 09

100

009

97 33

6866

1134

0214

0196

0506

0002

3260

0947

0030

0280

0016

1706

0503

767

Mg-hornblende

core

45 43

249

10 3

000

11 99

022

14 50

11 14

133

008

97 48

6524

1476

0267

0269

0644

0000

3103

0796

0027

0370

0015

1715

0703

838


1194

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein


alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam


Blundythermometer

(1994)Errors

are40

C


1195






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208



(a) (b)

(c) (d)

(e) (f)

olopx

kel

pl

ol

hbol

amcpx

cpx

hb

chl

am+pl+mt

idg

am

hb

pl

hb

ol

cpx

opx

mt

pl



1185





2 Km

3

4

5

6

7


High T

Very High T

0 High T

Upper Crust

LID

Lower Crust

MohoMTZ

DEPTH1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27


0

10

20

30

40

50

60

70

80

90

100

SD root

zone

upper

gabbros

middle

gabbros

lower

gabbros

MTZ

BHb-GHb CPX

Chl-Amph core OL

Chl-Amph rim OL

0

5

10

15

20

25

30

SD root

zone

upper

gabbros

middle

gabbros

lower

gabbros

MTZ

Opx OL

BHb OL

No VHTHT

Unaltered OL core

HT

VHT

(a)

(b)

Plst def

gabbros



1186







(b) (c)(a)

(d) (e)

thulite

pistacite

white microvein

white vein

green vein

green vein

gabbroic dike

epidote vein

gabbroic dike



1187





(a) (b) (c)

g(e)(d)


hwhite vein

hblpl

pcpx


eediabasedikdike







1188







O---Sr isotopes







1189


Oxygen isotopes


RESULTS











1190




Sam

ple

nam

eSite

Locationin

gab

broic

section

Typ

eofrock

Distance

to

Moho(km)

Parag

enesis

Alteration

87Sr

86Srinitial1

d18O

()2

94MA2

Maq

sad

From

MTZ

Layered

gab

bro

0Olivine(M

gno74---75)3

OPXco

ronas

(Mgno78---79)

WRfrac14

070322

WRfrac14

thorn495

CPX

Palegreen

Am

(cumact)

CPXfrac14

070324

nd

Plagioclase(A


Nolow-T

alteration

Plfrac14

070322

Plfrac14

thorn479

Solidfluid

inclusionsin

Pl

97OA128b

Wad

iWaryiah

From

lower

gab

bro

Layered

gab

bro

1CPX

Low-T

alteration

WRfrac14

070333

nd

Plagioclase(A

n85---87)

Prehnitemicroveins

CPXfrac14

070422

CPXfrac14

thorn523

Plfrac14

070328

Plfrac14

thorn414

01OA41d2

Wad

iGideah

From

upper

gab

bro

Gab

bro

patch

in

laminated

gab

bro

36

CPXrecrystallized


(An57---87)norm

alzoning

Black

pargasitic

honblende

WRfrac14

070351

CPXfrac14

070378

Plfrac14

070426

WRfrac14

thorn480

nd

Plfrac14

thorn504

Hbdfrac14

070355

nd

01OA19aamp

dWad

iWaryiah

Inlayeredgab

bro

Gab

broic

dyke

01

Olivine

OPXpoikilitic

WRfrac14

070341

WRfrac14

thorn567

CPX

Black

pargasite

Hbdfrac14

070324

Hbdfrac14

thorn287

Plagioclase(A

n73---95)


Plfrac14

nd

Plfrac14

thorn10 09

Hem

atite

WRfrac14

070418

nd

Green

Mg-hornblende

Acthornblende

Epidote

02OA90b

Wad

iAl-Abyad

Inlayeredgab

bro

Dioriticdyke

015

Green

Mg-hornblende

Hbdfrac14

070427

Hbdfrac14

thorn239

Plagioclase(A

n83---87)

Plfrac14

070387

Plfrac14

thorn498

Solidfluid

inclusionsin

plagioclase

01OA15f

Wad

iWaryiah

Inlayeredgab

bro

Comb-textured

gab

broic

dyke

025

CPXidiomorphic

Plagioclase(A

n95---99)norm

alzoning

BrownMg-H

ornblende

WRfrac14

070458

nd

02OA43a

Wad

iMayah

Inlayeredgab

bro

vein

Green

amphibole

1Palegreen


Plagioclase(A

n91---97)in

reactionmargin

Hbdfrac14

070431

Hbdfrac14

thorn310

01OA36b

Wad

iGideah

Inlayeredgab

bro

epidosite

dyke

25

CPX

Epidote

WRfrac14

070519

nd

Plagioclase

Epfrac14

070554

nd

CPXclinopyroxene

Plplagioclase

OPXorthopyroxene

Amam

phibolecu

mcu

mmingtonite

actactinolite


Epep

idotend

notdetermined

187Sr


95Ma(H

acker1994)Errors


inTab

le4

2Analyticalerrors

oftheoxygen

isotopevalues

are02

(2s)

3Mgnumber


Fe)

4Percentageofan

orthitein

plagioclase


1191







Blundy (1994)


rim core rim core

01 OA41d2 878 953 ------- -------

01 OA19a 935 974 825 869

01 OA19d 890 933 789 -------

02 OA37b ------- ------- 816 849

02 OA90b ------- ------- 859 833


1192










(wt )



gabb dyke


(margin)

SiO2 4830 4815 4749 4524 4339 4799 389 4371

Al2O3 2785 2032 2438 1474 1246 1192 2752 1646

Fe2O3 328 266 404 981 1204 592 381 623

MnO 003 004 005 014 016 006 008 014

MgO 405 737 427 1031 1686 1326 187 739

CaO 1289 1908 1477 1235 1156 166 2471 2339

Na2O 292 123 257 258 111 075 000 013

K2O 000 000 009 006 000 000 000 000

TiO2 005 017 063 230 064 086 013 042

P2O5 008 007 013 018 009 013 007 010

LOI 033 076 138 216 161 237 274 190

Total 9978 9985 998 9987 9992 9986 9983 9987



1193


aofselectedam

phibolespaired


Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

01OA19a

Mg-hornblende

core

45 60

26

10 78

009

860

015

16 56

12 00

212

007

96 72

6552

1448

0366

0083

0552

0004

3409

0594

0016

0611

0018

1843

0903

899

Mg-hornblende

core

47 99

263

850

002

897

011

16 61

12 10

160

020

96 36

6894

1106

0334

0028

0483

0002

3557

0594

0014

0446

0036

1862

0892

834

Mg-hornblende

rim

51 17

247

596

001

761

014

18 11

12 19

103

010

96 47

7257

0743

0253

0016

0414

0001

3828

0488

0016

0284

0018

1853

0894

820

Mg-hornblende

rim

47 50

291

920

004

880

014

16 46

11 95

174

008

96 07

6835

1165

0396

0015

0506

0005

3529

0552

0017

0486

0015

1843

0887

825

Mg-hornblende

rim

49 57

269

742

000

799

017

18 07

12 02

133

014

96 88

7013

0987

0261

0018

0575

0000

3811

0371

0020

0365

0026

1821

0860

831

Mg-hornblende

core

47 83

181

872

003

840

011

14 48

12 18

159

008

93 59

6814

1186

0279

0018

0644

0004

3711

0357

0013

0438

0015

1859

0907

874

Pargasite

rim

42 15

249

11 87

024

10 07

013

13 84

11 43

263

032

96 61

6188

1812

0242

0434

0299

0028

3028

0937

0016

0749

0059

1797

0804

972

Pargasite

rim

42 22

260

11 86

026

10 21

011

13 71

11 48

253

032

96 59

6201

1799

0254

0429

0299

0030

3001

0955

0014

0720

0060

1807

0803

962

Pargasite

core

42 05

263

11 45

030

10 19

011

13 80

11 47

246

032

96 46

6189

1811

0175

0478

0299

0035

3029

0956

0014

0702

0060

1809

0767

974

Pargasite

rim

42 36

247

11 90

016

945

013

14 16

11 76

249

026

95 98

6239

1761

0305

0366

0276

0019

3109

0888

0016

0710

0049

1856

0818

926

Pargasite

core

42 50

291

11 64

016

984

015

14 22

11 41

256

034

96 69

6219

1781

0227

0426

0322

0018

3103

0883

0018

0727

0063

1789

0812

974

Pargasite

rim

42 76

270

12 03

017

920

012

14 87

11 82

244

025

96 73

6224

1776

0880

0335

0368

0020

3226

0752

0015

0689

0047

1843

0841

941

Pargasite

rim

42 13

181

13 54

016

921

009

12 77

12 13

254

032

96 98

6172

1828

0510

0450

0000

0018

2788

1129

0011

0721

0059

1905

0841

874

01OA19d

Mg-hornblende

49 26

047

624

011

11 46

017

15 39

12 21

108

009

96 48

7137

0863

0202

0051

0437

0013

3323

0951

0021

0302

0018

1896

0768

771

Mg-hornblende

46 03

287

932

018

906

017

14 77

12 87

193

007

97 28

6672

1328

0265

0313

0046

0021

3191

1053

0021

0542

0012

1999

0758

808

Pargasite

41 89

429

11 65

008

11 03

017

13 52

11 37

259

017

96 77

6159

1841

0179

0474

0345

0010

2963

1012

0021

0739

0032

1791

0770

975

Pargasite

rim

42 80

340

11 16

009

11 01

018

13 73

11 67

240

022

96 67

6293

1707

0226

0376

0322

0010

3009

1032

0022

0684

0041

1839

0605

880

Pargasite

core

42 58

351

11 27

006

11 63

018

13 51

11 46

239

022

96 82

6257

1743

0209

0387

0391

0007

2959

1039

0023

0680

0042

1804

0595

893

Pargasite

rim

42 14

393

11 28

006

11 71

014

13 35

11 33

235

033

96 62

6214

1786

0174

0435

0391

0007

2935

1054

0018

0673

0062

1790

0519

901

Pargasite

core

41 56

420

12 05

006

11 57

016

12 51

11 35

249

027

96 24

6168

1832

0277

0469

0276

0007

2768

1160

0021

0718

0052

1805

0537

882

Pargasite

core

41 33

438

11 49

008

11 66

015

13 35

11 45

264

026

96 80

6105

1894

0107

0487

0368

0009

2941

1073

0019

0757

0048

1813

0537

942

Pargasite

41 08

446

12 39

012

11 35

017

13 13

11 36

263

015

96 85

6049

1951

0199

0494

0368

0014

2882

1030

0021

0752

0027

1792

0758

975

02OA37b

Mg-hornblende

rim

45 15

260

984

002

13 28

019

14 01

10 87

128

009

97 33

6527

1473

0203

0283

0690

0002

3018

0915

0023

0360

0016

1683

0562

828

Mg-hornblende

rim

44 72

263

988

004

13 23

021

14 01

10 78

133

009

96 92

6494

1506

0185

0287

0713

0005

3032

0894

0025

0374

0018

1677

0593

854

Mg-hornblende

rim

45 68

247

935

004

12 87

020

14 10

11 00

121

011

97 02

6621

1379

0218

0269

0598

0004

3045

0962

0024

0341

0020

1708

0562

815

Mg-hornblende

core

43 94

291

10 87

001

12 60

023

13 73

10 59

142

011

96 39

6410

1590

0278

0319

0644

0001

2985

0893

0028

0401

0021

1655

0710

860

Mg-hornblende

core

44 62

270

10 37

001

12 66

019

14 12

10 58

140

008

96 73

6479

1521

0253

0294

0644

0001

3057

0893

0023

0395

0014

1646

0674

851

Mg-hornblende

rim

47 79

181

796

002

12 09

025

15 22

11 09

100

009

97 33

6866

1134

0214

0196

0506

0002

3260

0947

0030

0280

0016

1706

0503

767

Mg-hornblende

core

45 43

249

10 3

000

11 99

022

14 50

11 14

133

008

97 48

6524

1476

0267

0269

0644

0000

3103

0796

0027

0370

0015

1715

0703

838


1194

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein


alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam


Blundythermometer

(1994)Errors

are40

C


1195






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208





2 Km

3

4

5

6

7


High T

Very High T

0 High T

Upper Crust

LID

Lower Crust

MohoMTZ

DEPTH1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27


0

10

20

30

40

50

60

70

80

90

100

SD root

zone

upper

gabbros

middle

gabbros

lower

gabbros

MTZ

BHb-GHb CPX

Chl-Amph core OL

Chl-Amph rim OL

0

5

10

15

20

25

30

SD root

zone

upper

gabbros

middle

gabbros

lower

gabbros

MTZ

Opx OL

BHb OL

No VHTHT

Unaltered OL core

HT

VHT

(a)

(b)

Plst def

gabbros



1186







(b) (c)(a)

(d) (e)

thulite

pistacite

white microvein

white vein

green vein

green vein

gabbroic dike

epidote vein

gabbroic dike



1187





(a) (b) (c)

g(e)(d)


hwhite vein

hblpl

pcpx


eediabasedikdike







1188







O---Sr isotopes







1189


Oxygen isotopes


RESULTS











1190




Sam

ple

nam

eSite

Locationin

gab

broic

section

Typ

eofrock

Distance

to

Moho(km)

Parag

enesis

Alteration

87Sr

86Srinitial1

d18O

()2

94MA2

Maq

sad

From

MTZ

Layered

gab

bro

0Olivine(M

gno74---75)3

OPXco

ronas

(Mgno78---79)

WRfrac14

070322

WRfrac14

thorn495

CPX

Palegreen

Am

(cumact)

CPXfrac14

070324

nd

Plagioclase(A


Nolow-T

alteration

Plfrac14

070322

Plfrac14

thorn479

Solidfluid

inclusionsin

Pl

97OA128b

Wad

iWaryiah

From

lower

gab

bro

Layered

gab

bro

1CPX

Low-T

alteration

WRfrac14

070333

nd

Plagioclase(A

n85---87)

Prehnitemicroveins

CPXfrac14

070422

CPXfrac14

thorn523

Plfrac14

070328

Plfrac14

thorn414

01OA41d2

Wad

iGideah

From

upper

gab

bro

Gab

bro

patch

in

laminated

gab

bro

36

CPXrecrystallized


(An57---87)norm

alzoning

Black

pargasitic

honblende

WRfrac14

070351

CPXfrac14

070378

Plfrac14

070426

WRfrac14

thorn480

nd

Plfrac14

thorn504

Hbdfrac14

070355

nd

01OA19aamp

dWad

iWaryiah

Inlayeredgab

bro

Gab

broic

dyke

01

Olivine

OPXpoikilitic

WRfrac14

070341

WRfrac14

thorn567

CPX

Black

pargasite

Hbdfrac14

070324

Hbdfrac14

thorn287

Plagioclase(A

n73---95)


Plfrac14

nd

Plfrac14

thorn10 09

Hem

atite

WRfrac14

070418

nd

Green

Mg-hornblende

Acthornblende

Epidote

02OA90b

Wad

iAl-Abyad

Inlayeredgab

bro

Dioriticdyke

015

Green

Mg-hornblende

Hbdfrac14

070427

Hbdfrac14

thorn239

Plagioclase(A

n83---87)

Plfrac14

070387

Plfrac14

thorn498

Solidfluid

inclusionsin

plagioclase

01OA15f

Wad

iWaryiah

Inlayeredgab

bro

Comb-textured

gab

broic

dyke

025

CPXidiomorphic

Plagioclase(A

n95---99)norm

alzoning

BrownMg-H

ornblende

WRfrac14

070458

nd

02OA43a

Wad

iMayah

Inlayeredgab

bro

vein

Green

amphibole

1Palegreen


Plagioclase(A

n91---97)in

reactionmargin

Hbdfrac14

070431

Hbdfrac14

thorn310

01OA36b

Wad

iGideah

Inlayeredgab

bro

epidosite

dyke

25

CPX

Epidote

WRfrac14

070519

nd

Plagioclase

Epfrac14

070554

nd

CPXclinopyroxene

Plplagioclase

OPXorthopyroxene

Amam

phibolecu

mcu

mmingtonite

actactinolite


Epep

idotend

notdetermined

187Sr


95Ma(H

acker1994)Errors


inTab

le4

2Analyticalerrors

oftheoxygen

isotopevalues

are02

(2s)

3Mgnumber


Fe)

4Percentageofan

orthitein

plagioclase


1191







Blundy (1994)


rim core rim core

01 OA41d2 878 953 ------- -------

01 OA19a 935 974 825 869

01 OA19d 890 933 789 -------

02 OA37b ------- ------- 816 849

02 OA90b ------- ------- 859 833


1192










(wt )



gabb dyke


(margin)

SiO2 4830 4815 4749 4524 4339 4799 389 4371

Al2O3 2785 2032 2438 1474 1246 1192 2752 1646

Fe2O3 328 266 404 981 1204 592 381 623

MnO 003 004 005 014 016 006 008 014

MgO 405 737 427 1031 1686 1326 187 739

CaO 1289 1908 1477 1235 1156 166 2471 2339

Na2O 292 123 257 258 111 075 000 013

K2O 000 000 009 006 000 000 000 000

TiO2 005 017 063 230 064 086 013 042

P2O5 008 007 013 018 009 013 007 010

LOI 033 076 138 216 161 237 274 190

Total 9978 9985 998 9987 9992 9986 9983 9987



1193


aofselectedam

phibolespaired


Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

01OA19a

Mg-hornblende

core

45 60

26

10 78

009

860

015

16 56

12 00

212

007

96 72

6552

1448

0366

0083

0552

0004

3409

0594

0016

0611

0018

1843

0903

899

Mg-hornblende

core

47 99

263

850

002

897

011

16 61

12 10

160

020

96 36

6894

1106

0334

0028

0483

0002

3557

0594

0014

0446

0036

1862

0892

834

Mg-hornblende

rim

51 17

247

596

001

761

014

18 11

12 19

103

010

96 47

7257

0743

0253

0016

0414

0001

3828

0488

0016

0284

0018

1853

0894

820

Mg-hornblende

rim

47 50

291

920

004

880

014

16 46

11 95

174

008

96 07

6835

1165

0396

0015

0506

0005

3529

0552

0017

0486

0015

1843

0887

825

Mg-hornblende

rim

49 57

269

742

000

799

017

18 07

12 02

133

014

96 88

7013

0987

0261

0018

0575

0000

3811

0371

0020

0365

0026

1821

0860

831

Mg-hornblende

core

47 83

181

872

003

840

011

14 48

12 18

159

008

93 59

6814

1186

0279

0018

0644

0004

3711

0357

0013

0438

0015

1859

0907

874

Pargasite

rim

42 15

249

11 87

024

10 07

013

13 84

11 43

263

032

96 61

6188

1812

0242

0434

0299

0028

3028

0937

0016

0749

0059

1797

0804

972

Pargasite

rim

42 22

260

11 86

026

10 21

011

13 71

11 48

253

032

96 59

6201

1799

0254

0429

0299

0030

3001

0955

0014

0720

0060

1807

0803

962

Pargasite

core

42 05

263

11 45

030

10 19

011

13 80

11 47

246

032

96 46

6189

1811

0175

0478

0299

0035

3029

0956

0014

0702

0060

1809

0767

974

Pargasite

rim

42 36

247

11 90

016

945

013

14 16

11 76

249

026

95 98

6239

1761

0305

0366

0276

0019

3109

0888

0016

0710

0049

1856

0818

926

Pargasite

core

42 50

291

11 64

016

984

015

14 22

11 41

256

034

96 69

6219

1781

0227

0426

0322

0018

3103

0883

0018

0727

0063

1789

0812

974

Pargasite

rim

42 76

270

12 03

017

920

012

14 87

11 82

244

025

96 73

6224

1776

0880

0335

0368

0020

3226

0752

0015

0689

0047

1843

0841

941

Pargasite

rim

42 13

181

13 54

016

921

009

12 77

12 13

254

032

96 98

6172

1828

0510

0450

0000

0018

2788

1129

0011

0721

0059

1905

0841

874

01OA19d

Mg-hornblende

49 26

047

624

011

11 46

017

15 39

12 21

108

009

96 48

7137

0863

0202

0051

0437

0013

3323

0951

0021

0302

0018

1896

0768

771

Mg-hornblende

46 03

287

932

018

906

017

14 77

12 87

193

007

97 28

6672

1328

0265

0313

0046

0021

3191

1053

0021

0542

0012

1999

0758

808

Pargasite

41 89

429

11 65

008

11 03

017

13 52

11 37

259

017

96 77

6159

1841

0179

0474

0345

0010

2963

1012

0021

0739

0032

1791

0770

975

Pargasite

rim

42 80

340

11 16

009

11 01

018

13 73

11 67

240

022

96 67

6293

1707

0226

0376

0322

0010

3009

1032

0022

0684

0041

1839

0605

880

Pargasite

core

42 58

351

11 27

006

11 63

018

13 51

11 46

239

022

96 82

6257

1743

0209

0387

0391

0007

2959

1039

0023

0680

0042

1804

0595

893

Pargasite

rim

42 14

393

11 28

006

11 71

014

13 35

11 33

235

033

96 62

6214

1786

0174

0435

0391

0007

2935

1054

0018

0673

0062

1790

0519

901

Pargasite

core

41 56

420

12 05

006

11 57

016

12 51

11 35

249

027

96 24

6168

1832

0277

0469

0276

0007

2768

1160

0021

0718

0052

1805

0537

882

Pargasite

core

41 33

438

11 49

008

11 66

015

13 35

11 45

264

026

96 80

6105

1894

0107

0487

0368

0009

2941

1073

0019

0757

0048

1813

0537

942

Pargasite

41 08

446

12 39

012

11 35

017

13 13

11 36

263

015

96 85

6049

1951

0199

0494

0368

0014

2882

1030

0021

0752

0027

1792

0758

975

02OA37b

Mg-hornblende

rim

45 15

260

984

002

13 28

019

14 01

10 87

128

009

97 33

6527

1473

0203

0283

0690

0002

3018

0915

0023

0360

0016

1683

0562

828

Mg-hornblende

rim

44 72

263

988

004

13 23

021

14 01

10 78

133

009

96 92

6494

1506

0185

0287

0713

0005

3032

0894

0025

0374

0018

1677

0593

854

Mg-hornblende

rim

45 68

247

935

004

12 87

020

14 10

11 00

121

011

97 02

6621

1379

0218

0269

0598

0004

3045

0962

0024

0341

0020

1708

0562

815

Mg-hornblende

core

43 94

291

10 87

001

12 60

023

13 73

10 59

142

011

96 39

6410

1590

0278

0319

0644

0001

2985

0893

0028

0401

0021

1655

0710

860

Mg-hornblende

core

44 62

270

10 37

001

12 66

019

14 12

10 58

140

008

96 73

6479

1521

0253

0294

0644

0001

3057

0893

0023

0395

0014

1646

0674

851

Mg-hornblende

rim

47 79

181

796

002

12 09

025

15 22

11 09

100

009

97 33

6866

1134

0214

0196

0506

0002

3260

0947

0030

0280

0016

1706

0503

767

Mg-hornblende

core

45 43

249

10 3

000

11 99

022

14 50

11 14

133

008

97 48

6524

1476

0267

0269

0644

0000

3103

0796

0027

0370

0015

1715

0703

838


1194

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein


alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam


Blundythermometer

(1994)Errors

are40

C


1195






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208







(b) (c)(a)

(d) (e)

thulite

pistacite

white microvein

white vein

green vein

green vein

gabbroic dike

epidote vein

gabbroic dike



1187





(a) (b) (c)

g(e)(d)


hwhite vein

hblpl

pcpx


eediabasedikdike







1188







O---Sr isotopes







1189


Oxygen isotopes


RESULTS











1190




Sam

ple

nam

eSite

Locationin

gab

broic

section

Typ

eofrock

Distance

to

Moho(km)

Parag

enesis

Alteration

87Sr

86Srinitial1

d18O

()2

94MA2

Maq

sad

From

MTZ

Layered

gab

bro

0Olivine(M

gno74---75)3

OPXco

ronas

(Mgno78---79)

WRfrac14

070322

WRfrac14

thorn495

CPX

Palegreen

Am

(cumact)

CPXfrac14

070324

nd

Plagioclase(A


Nolow-T

alteration

Plfrac14

070322

Plfrac14

thorn479

Solidfluid

inclusionsin

Pl

97OA128b

Wad

iWaryiah

From

lower

gab

bro

Layered

gab

bro

1CPX

Low-T

alteration

WRfrac14

070333

nd

Plagioclase(A

n85---87)

Prehnitemicroveins

CPXfrac14

070422

CPXfrac14

thorn523

Plfrac14

070328

Plfrac14

thorn414

01OA41d2

Wad

iGideah

From

upper

gab

bro

Gab

bro

patch

in

laminated

gab

bro

36

CPXrecrystallized


(An57---87)norm

alzoning

Black

pargasitic

honblende

WRfrac14

070351

CPXfrac14

070378

Plfrac14

070426

WRfrac14

thorn480

nd

Plfrac14

thorn504

Hbdfrac14

070355

nd

01OA19aamp

dWad

iWaryiah

Inlayeredgab

bro

Gab

broic

dyke

01

Olivine

OPXpoikilitic

WRfrac14

070341

WRfrac14

thorn567

CPX

Black

pargasite

Hbdfrac14

070324

Hbdfrac14

thorn287

Plagioclase(A

n73---95)


Plfrac14

nd

Plfrac14

thorn10 09

Hem

atite

WRfrac14

070418

nd

Green

Mg-hornblende

Acthornblende

Epidote

02OA90b

Wad

iAl-Abyad

Inlayeredgab

bro

Dioriticdyke

015

Green

Mg-hornblende

Hbdfrac14

070427

Hbdfrac14

thorn239

Plagioclase(A

n83---87)

Plfrac14

070387

Plfrac14

thorn498

Solidfluid

inclusionsin

plagioclase

01OA15f

Wad

iWaryiah

Inlayeredgab

bro

Comb-textured

gab

broic

dyke

025

CPXidiomorphic

Plagioclase(A

n95---99)norm

alzoning

BrownMg-H

ornblende

WRfrac14

070458

nd

02OA43a

Wad

iMayah

Inlayeredgab

bro

vein

Green

amphibole

1Palegreen


Plagioclase(A

n91---97)in

reactionmargin

Hbdfrac14

070431

Hbdfrac14

thorn310

01OA36b

Wad

iGideah

Inlayeredgab

bro

epidosite

dyke

25

CPX

Epidote

WRfrac14

070519

nd

Plagioclase

Epfrac14

070554

nd

CPXclinopyroxene

Plplagioclase

OPXorthopyroxene

Amam

phibolecu

mcu

mmingtonite

actactinolite


Epep

idotend

notdetermined

187Sr


95Ma(H

acker1994)Errors


inTab

le4

2Analyticalerrors

oftheoxygen

isotopevalues

are02

(2s)

3Mgnumber


Fe)

4Percentageofan

orthitein

plagioclase


1191







Blundy (1994)


rim core rim core

01 OA41d2 878 953 ------- -------

01 OA19a 935 974 825 869

01 OA19d 890 933 789 -------

02 OA37b ------- ------- 816 849

02 OA90b ------- ------- 859 833


1192










(wt )



gabb dyke


(margin)

SiO2 4830 4815 4749 4524 4339 4799 389 4371

Al2O3 2785 2032 2438 1474 1246 1192 2752 1646

Fe2O3 328 266 404 981 1204 592 381 623

MnO 003 004 005 014 016 006 008 014

MgO 405 737 427 1031 1686 1326 187 739

CaO 1289 1908 1477 1235 1156 166 2471 2339

Na2O 292 123 257 258 111 075 000 013

K2O 000 000 009 006 000 000 000 000

TiO2 005 017 063 230 064 086 013 042

P2O5 008 007 013 018 009 013 007 010

LOI 033 076 138 216 161 237 274 190

Total 9978 9985 998 9987 9992 9986 9983 9987



1193


aofselectedam

phibolespaired


Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

01OA19a

Mg-hornblende

core

45 60

26

10 78

009

860

015

16 56

12 00

212

007

96 72

6552

1448

0366

0083

0552

0004

3409

0594

0016

0611

0018

1843

0903

899

Mg-hornblende

core

47 99

263

850

002

897

011

16 61

12 10

160

020

96 36

6894

1106

0334

0028

0483

0002

3557

0594

0014

0446

0036

1862

0892

834

Mg-hornblende

rim

51 17

247

596

001

761

014

18 11

12 19

103

010

96 47

7257

0743

0253

0016

0414

0001

3828

0488

0016

0284

0018

1853

0894

820

Mg-hornblende

rim

47 50

291

920

004

880

014

16 46

11 95

174

008

96 07

6835

1165

0396

0015

0506

0005

3529

0552

0017

0486

0015

1843

0887

825

Mg-hornblende

rim

49 57

269

742

000

799

017

18 07

12 02

133

014

96 88

7013

0987

0261

0018

0575

0000

3811

0371

0020

0365

0026

1821

0860

831

Mg-hornblende

core

47 83

181

872

003

840

011

14 48

12 18

159

008

93 59

6814

1186

0279

0018

0644

0004

3711

0357

0013

0438

0015

1859

0907

874

Pargasite

rim

42 15

249

11 87

024

10 07

013

13 84

11 43

263

032

96 61

6188

1812

0242

0434

0299

0028

3028

0937

0016

0749

0059

1797

0804

972

Pargasite

rim

42 22

260

11 86

026

10 21

011

13 71

11 48

253

032

96 59

6201

1799

0254

0429

0299

0030

3001

0955

0014

0720

0060

1807

0803

962

Pargasite

core

42 05

263

11 45

030

10 19

011

13 80

11 47

246

032

96 46

6189

1811

0175

0478

0299

0035

3029

0956

0014

0702

0060

1809

0767

974

Pargasite

rim

42 36

247

11 90

016

945

013

14 16

11 76

249

026

95 98

6239

1761

0305

0366

0276

0019

3109

0888

0016

0710

0049

1856

0818

926

Pargasite

core

42 50

291

11 64

016

984

015

14 22

11 41

256

034

96 69

6219

1781

0227

0426

0322

0018

3103

0883

0018

0727

0063

1789

0812

974

Pargasite

rim

42 76

270

12 03

017

920

012

14 87

11 82

244

025

96 73

6224

1776

0880

0335

0368

0020

3226

0752

0015

0689

0047

1843

0841

941

Pargasite

rim

42 13

181

13 54

016

921

009

12 77

12 13

254

032

96 98

6172

1828

0510

0450

0000

0018

2788

1129

0011

0721

0059

1905

0841

874

01OA19d

Mg-hornblende

49 26

047

624

011

11 46

017

15 39

12 21

108

009

96 48

7137

0863

0202

0051

0437

0013

3323

0951

0021

0302

0018

1896

0768

771

Mg-hornblende

46 03

287

932

018

906

017

14 77

12 87

193

007

97 28

6672

1328

0265

0313

0046

0021

3191

1053

0021

0542

0012

1999

0758

808

Pargasite

41 89

429

11 65

008

11 03

017

13 52

11 37

259

017

96 77

6159

1841

0179

0474

0345

0010

2963

1012

0021

0739

0032

1791

0770

975

Pargasite

rim

42 80

340

11 16

009

11 01

018

13 73

11 67

240

022

96 67

6293

1707

0226

0376

0322

0010

3009

1032

0022

0684

0041

1839

0605

880

Pargasite

core

42 58

351

11 27

006

11 63

018

13 51

11 46

239

022

96 82

6257

1743

0209

0387

0391

0007

2959

1039

0023

0680

0042

1804

0595

893

Pargasite

rim

42 14

393

11 28

006

11 71

014

13 35

11 33

235

033

96 62

6214

1786

0174

0435

0391

0007

2935

1054

0018

0673

0062

1790

0519

901

Pargasite

core

41 56

420

12 05

006

11 57

016

12 51

11 35

249

027

96 24

6168

1832

0277

0469

0276

0007

2768

1160

0021

0718

0052

1805

0537

882

Pargasite

core

41 33

438

11 49

008

11 66

015

13 35

11 45

264

026

96 80

6105

1894

0107

0487

0368

0009

2941

1073

0019

0757

0048

1813

0537

942

Pargasite

41 08

446

12 39

012

11 35

017

13 13

11 36

263

015

96 85

6049

1951

0199

0494

0368

0014

2882

1030

0021

0752

0027

1792

0758

975

02OA37b

Mg-hornblende

rim

45 15

260

984

002

13 28

019

14 01

10 87

128

009

97 33

6527

1473

0203

0283

0690

0002

3018

0915

0023

0360

0016

1683

0562

828

Mg-hornblende

rim

44 72

263

988

004

13 23

021

14 01

10 78

133

009

96 92

6494

1506

0185

0287

0713

0005

3032

0894

0025

0374

0018

1677

0593

854

Mg-hornblende

rim

45 68

247

935

004

12 87

020

14 10

11 00

121

011

97 02

6621

1379

0218

0269

0598

0004

3045

0962

0024

0341

0020

1708

0562

815

Mg-hornblende

core

43 94

291

10 87

001

12 60

023

13 73

10 59

142

011

96 39

6410

1590

0278

0319

0644

0001

2985

0893

0028

0401

0021

1655

0710

860

Mg-hornblende

core

44 62

270

10 37

001

12 66

019

14 12

10 58

140

008

96 73

6479

1521

0253

0294

0644

0001

3057

0893

0023

0395

0014

1646

0674

851

Mg-hornblende

rim

47 79

181

796

002

12 09

025

15 22

11 09

100

009

97 33

6866

1134

0214

0196

0506

0002

3260

0947

0030

0280

0016

1706

0503

767

Mg-hornblende

core

45 43

249

10 3

000

11 99

022

14 50

11 14

133

008

97 48

6524

1476

0267

0269

0644

0000

3103

0796

0027

0370

0015

1715

0703

838


1194

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein


alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam


Blundythermometer

(1994)Errors

are40

C


1195






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208





(a) (b) (c)

g(e)(d)


hwhite vein

hblpl

pcpx


eediabasedikdike







1188







O---Sr isotopes







1189


Oxygen isotopes


RESULTS











1190




Sam

ple

nam

eSite

Locationin

gab

broic

section

Typ

eofrock

Distance

to

Moho(km)

Parag

enesis

Alteration

87Sr

86Srinitial1

d18O

()2

94MA2

Maq

sad

From

MTZ

Layered

gab

bro

0Olivine(M

gno74---75)3

OPXco

ronas

(Mgno78---79)

WRfrac14

070322

WRfrac14

thorn495

CPX

Palegreen

Am

(cumact)

CPXfrac14

070324

nd

Plagioclase(A


Nolow-T

alteration

Plfrac14

070322

Plfrac14

thorn479

Solidfluid

inclusionsin

Pl

97OA128b

Wad

iWaryiah

From

lower

gab

bro

Layered

gab

bro

1CPX

Low-T

alteration

WRfrac14

070333

nd

Plagioclase(A

n85---87)

Prehnitemicroveins

CPXfrac14

070422

CPXfrac14

thorn523

Plfrac14

070328

Plfrac14

thorn414

01OA41d2

Wad

iGideah

From

upper

gab

bro

Gab

bro

patch

in

laminated

gab

bro

36

CPXrecrystallized


(An57---87)norm

alzoning

Black

pargasitic

honblende

WRfrac14

070351

CPXfrac14

070378

Plfrac14

070426

WRfrac14

thorn480

nd

Plfrac14

thorn504

Hbdfrac14

070355

nd

01OA19aamp

dWad

iWaryiah

Inlayeredgab

bro

Gab

broic

dyke

01

Olivine

OPXpoikilitic

WRfrac14

070341

WRfrac14

thorn567

CPX

Black

pargasite

Hbdfrac14

070324

Hbdfrac14

thorn287

Plagioclase(A

n73---95)


Plfrac14

nd

Plfrac14

thorn10 09

Hem

atite

WRfrac14

070418

nd

Green

Mg-hornblende

Acthornblende

Epidote

02OA90b

Wad

iAl-Abyad

Inlayeredgab

bro

Dioriticdyke

015

Green

Mg-hornblende

Hbdfrac14

070427

Hbdfrac14

thorn239

Plagioclase(A

n83---87)

Plfrac14

070387

Plfrac14

thorn498

Solidfluid

inclusionsin

plagioclase

01OA15f

Wad

iWaryiah

Inlayeredgab

bro

Comb-textured

gab

broic

dyke

025

CPXidiomorphic

Plagioclase(A

n95---99)norm

alzoning

BrownMg-H

ornblende

WRfrac14

070458

nd

02OA43a

Wad

iMayah

Inlayeredgab

bro

vein

Green

amphibole

1Palegreen


Plagioclase(A

n91---97)in

reactionmargin

Hbdfrac14

070431

Hbdfrac14

thorn310

01OA36b

Wad

iGideah

Inlayeredgab

bro

epidosite

dyke

25

CPX

Epidote

WRfrac14

070519

nd

Plagioclase

Epfrac14

070554

nd

CPXclinopyroxene

Plplagioclase

OPXorthopyroxene

Amam

phibolecu

mcu

mmingtonite

actactinolite


Epep

idotend

notdetermined

187Sr


95Ma(H

acker1994)Errors


inTab

le4

2Analyticalerrors

oftheoxygen

isotopevalues

are02

(2s)

3Mgnumber


Fe)

4Percentageofan

orthitein

plagioclase


1191







Blundy (1994)


rim core rim core

01 OA41d2 878 953 ------- -------

01 OA19a 935 974 825 869

01 OA19d 890 933 789 -------

02 OA37b ------- ------- 816 849

02 OA90b ------- ------- 859 833


1192










(wt )



gabb dyke


(margin)

SiO2 4830 4815 4749 4524 4339 4799 389 4371

Al2O3 2785 2032 2438 1474 1246 1192 2752 1646

Fe2O3 328 266 404 981 1204 592 381 623

MnO 003 004 005 014 016 006 008 014

MgO 405 737 427 1031 1686 1326 187 739

CaO 1289 1908 1477 1235 1156 166 2471 2339

Na2O 292 123 257 258 111 075 000 013

K2O 000 000 009 006 000 000 000 000

TiO2 005 017 063 230 064 086 013 042

P2O5 008 007 013 018 009 013 007 010

LOI 033 076 138 216 161 237 274 190

Total 9978 9985 998 9987 9992 9986 9983 9987



1193


aofselectedam

phibolespaired


Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

01OA19a

Mg-hornblende

core

45 60

26

10 78

009

860

015

16 56

12 00

212

007

96 72

6552

1448

0366

0083

0552

0004

3409

0594

0016

0611

0018

1843

0903

899

Mg-hornblende

core

47 99

263

850

002

897

011

16 61

12 10

160

020

96 36

6894

1106

0334

0028

0483

0002

3557

0594

0014

0446

0036

1862

0892

834

Mg-hornblende

rim

51 17

247

596

001

761

014

18 11

12 19

103

010

96 47

7257

0743

0253

0016

0414

0001

3828

0488

0016

0284

0018

1853

0894

820

Mg-hornblende

rim

47 50

291

920

004

880

014

16 46

11 95

174

008

96 07

6835

1165

0396

0015

0506

0005

3529

0552

0017

0486

0015

1843

0887

825

Mg-hornblende

rim

49 57

269

742

000

799

017

18 07

12 02

133

014

96 88

7013

0987

0261

0018

0575

0000

3811

0371

0020

0365

0026

1821

0860

831

Mg-hornblende

core

47 83

181

872

003

840

011

14 48

12 18

159

008

93 59

6814

1186

0279

0018

0644

0004

3711

0357

0013

0438

0015

1859

0907

874

Pargasite

rim

42 15

249

11 87

024

10 07

013

13 84

11 43

263

032

96 61

6188

1812

0242

0434

0299

0028

3028

0937

0016

0749

0059

1797

0804

972

Pargasite

rim

42 22

260

11 86

026

10 21

011

13 71

11 48

253

032

96 59

6201

1799

0254

0429

0299

0030

3001

0955

0014

0720

0060

1807

0803

962

Pargasite

core

42 05

263

11 45

030

10 19

011

13 80

11 47

246

032

96 46

6189

1811

0175

0478

0299

0035

3029

0956

0014

0702

0060

1809

0767

974

Pargasite

rim

42 36

247

11 90

016

945

013

14 16

11 76

249

026

95 98

6239

1761

0305

0366

0276

0019

3109

0888

0016

0710

0049

1856

0818

926

Pargasite

core

42 50

291

11 64

016

984

015

14 22

11 41

256

034

96 69

6219

1781

0227

0426

0322

0018

3103

0883

0018

0727

0063

1789

0812

974

Pargasite

rim

42 76

270

12 03

017

920

012

14 87

11 82

244

025

96 73

6224

1776

0880

0335

0368

0020

3226

0752

0015

0689

0047

1843

0841

941

Pargasite

rim

42 13

181

13 54

016

921

009

12 77

12 13

254

032

96 98

6172

1828

0510

0450

0000

0018

2788

1129

0011

0721

0059

1905

0841

874

01OA19d

Mg-hornblende

49 26

047

624

011

11 46

017

15 39

12 21

108

009

96 48

7137

0863

0202

0051

0437

0013

3323

0951

0021

0302

0018

1896

0768

771

Mg-hornblende

46 03

287

932

018

906

017

14 77

12 87

193

007

97 28

6672

1328

0265

0313

0046

0021

3191

1053

0021

0542

0012

1999

0758

808

Pargasite

41 89

429

11 65

008

11 03

017

13 52

11 37

259

017

96 77

6159

1841

0179

0474

0345

0010

2963

1012

0021

0739

0032

1791

0770

975

Pargasite

rim

42 80

340

11 16

009

11 01

018

13 73

11 67

240

022

96 67

6293

1707

0226

0376

0322

0010

3009

1032

0022

0684

0041

1839

0605

880

Pargasite

core

42 58

351

11 27

006

11 63

018

13 51

11 46

239

022

96 82

6257

1743

0209

0387

0391

0007

2959

1039

0023

0680

0042

1804

0595

893

Pargasite

rim

42 14

393

11 28

006

11 71

014

13 35

11 33

235

033

96 62

6214

1786

0174

0435

0391

0007

2935

1054

0018

0673

0062

1790

0519

901

Pargasite

core

41 56

420

12 05

006

11 57

016

12 51

11 35

249

027

96 24

6168

1832

0277

0469

0276

0007

2768

1160

0021

0718

0052

1805

0537

882

Pargasite

core

41 33

438

11 49

008

11 66

015

13 35

11 45

264

026

96 80

6105

1894

0107

0487

0368

0009

2941

1073

0019

0757

0048

1813

0537

942

Pargasite

41 08

446

12 39

012

11 35

017

13 13

11 36

263

015

96 85

6049

1951

0199

0494

0368

0014

2882

1030

0021

0752

0027

1792

0758

975

02OA37b

Mg-hornblende

rim

45 15

260

984

002

13 28

019

14 01

10 87

128

009

97 33

6527

1473

0203

0283

0690

0002

3018

0915

0023

0360

0016

1683

0562

828

Mg-hornblende

rim

44 72

263

988

004

13 23

021

14 01

10 78

133

009

96 92

6494

1506

0185

0287

0713

0005

3032

0894

0025

0374

0018

1677

0593

854

Mg-hornblende

rim

45 68

247

935

004

12 87

020

14 10

11 00

121

011

97 02

6621

1379

0218

0269

0598

0004

3045

0962

0024

0341

0020

1708

0562

815

Mg-hornblende

core

43 94

291

10 87

001

12 60

023

13 73

10 59

142

011

96 39

6410

1590

0278

0319

0644

0001

2985

0893

0028

0401

0021

1655

0710

860

Mg-hornblende

core

44 62

270

10 37

001

12 66

019

14 12

10 58

140

008

96 73

6479

1521

0253

0294

0644

0001

3057

0893

0023

0395

0014

1646

0674

851

Mg-hornblende

rim

47 79

181

796

002

12 09

025

15 22

11 09

100

009

97 33

6866

1134

0214

0196

0506

0002

3260

0947

0030

0280

0016

1706

0503

767

Mg-hornblende

core

45 43

249

10 3

000

11 99

022

14 50

11 14

133

008

97 48

6524

1476

0267

0269

0644

0000

3103

0796

0027

0370

0015

1715

0703

838


1194

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein


alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam


Blundythermometer

(1994)Errors

are40

C


1195






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208







O---Sr isotopes







1189


Oxygen isotopes


RESULTS











1190




Sam

ple

nam

eSite

Locationin

gab

broic

section

Typ

eofrock

Distance

to

Moho(km)

Parag

enesis

Alteration

87Sr

86Srinitial1

d18O

()2

94MA2

Maq

sad

From

MTZ

Layered

gab

bro

0Olivine(M

gno74---75)3

OPXco

ronas

(Mgno78---79)

WRfrac14

070322

WRfrac14

thorn495

CPX

Palegreen

Am

(cumact)

CPXfrac14

070324

nd

Plagioclase(A


Nolow-T

alteration

Plfrac14

070322

Plfrac14

thorn479

Solidfluid

inclusionsin

Pl

97OA128b

Wad

iWaryiah

From

lower

gab

bro

Layered

gab

bro

1CPX

Low-T

alteration

WRfrac14

070333

nd

Plagioclase(A

n85---87)

Prehnitemicroveins

CPXfrac14

070422

CPXfrac14

thorn523

Plfrac14

070328

Plfrac14

thorn414

01OA41d2

Wad

iGideah

From

upper

gab

bro

Gab

bro

patch

in

laminated

gab

bro

36

CPXrecrystallized


(An57---87)norm

alzoning

Black

pargasitic

honblende

WRfrac14

070351

CPXfrac14

070378

Plfrac14

070426

WRfrac14

thorn480

nd

Plfrac14

thorn504

Hbdfrac14

070355

nd

01OA19aamp

dWad

iWaryiah

Inlayeredgab

bro

Gab

broic

dyke

01

Olivine

OPXpoikilitic

WRfrac14

070341

WRfrac14

thorn567

CPX

Black

pargasite

Hbdfrac14

070324

Hbdfrac14

thorn287

Plagioclase(A

n73---95)


Plfrac14

nd

Plfrac14

thorn10 09

Hem

atite

WRfrac14

070418

nd

Green

Mg-hornblende

Acthornblende

Epidote

02OA90b

Wad

iAl-Abyad

Inlayeredgab

bro

Dioriticdyke

015

Green

Mg-hornblende

Hbdfrac14

070427

Hbdfrac14

thorn239

Plagioclase(A

n83---87)

Plfrac14

070387

Plfrac14

thorn498

Solidfluid

inclusionsin

plagioclase

01OA15f

Wad

iWaryiah

Inlayeredgab

bro

Comb-textured

gab

broic

dyke

025

CPXidiomorphic

Plagioclase(A

n95---99)norm

alzoning

BrownMg-H

ornblende

WRfrac14

070458

nd

02OA43a

Wad

iMayah

Inlayeredgab

bro

vein

Green

amphibole

1Palegreen


Plagioclase(A

n91---97)in

reactionmargin

Hbdfrac14

070431

Hbdfrac14

thorn310

01OA36b

Wad

iGideah

Inlayeredgab

bro

epidosite

dyke

25

CPX

Epidote

WRfrac14

070519

nd

Plagioclase

Epfrac14

070554

nd

CPXclinopyroxene

Plplagioclase

OPXorthopyroxene

Amam

phibolecu

mcu

mmingtonite

actactinolite


Epep

idotend

notdetermined

187Sr


95Ma(H

acker1994)Errors


inTab

le4

2Analyticalerrors

oftheoxygen

isotopevalues

are02

(2s)

3Mgnumber


Fe)

4Percentageofan

orthitein

plagioclase


1191







Blundy (1994)


rim core rim core

01 OA41d2 878 953 ------- -------

01 OA19a 935 974 825 869

01 OA19d 890 933 789 -------

02 OA37b ------- ------- 816 849

02 OA90b ------- ------- 859 833


1192










(wt )



gabb dyke


(margin)

SiO2 4830 4815 4749 4524 4339 4799 389 4371

Al2O3 2785 2032 2438 1474 1246 1192 2752 1646

Fe2O3 328 266 404 981 1204 592 381 623

MnO 003 004 005 014 016 006 008 014

MgO 405 737 427 1031 1686 1326 187 739

CaO 1289 1908 1477 1235 1156 166 2471 2339

Na2O 292 123 257 258 111 075 000 013

K2O 000 000 009 006 000 000 000 000

TiO2 005 017 063 230 064 086 013 042

P2O5 008 007 013 018 009 013 007 010

LOI 033 076 138 216 161 237 274 190

Total 9978 9985 998 9987 9992 9986 9983 9987



1193


aofselectedam

phibolespaired


Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

01OA19a

Mg-hornblende

core

45 60

26

10 78

009

860

015

16 56

12 00

212

007

96 72

6552

1448

0366

0083

0552

0004

3409

0594

0016

0611

0018

1843

0903

899

Mg-hornblende

core

47 99

263

850

002

897

011

16 61

12 10

160

020

96 36

6894

1106

0334

0028

0483

0002

3557

0594

0014

0446

0036

1862

0892

834

Mg-hornblende

rim

51 17

247

596

001

761

014

18 11

12 19

103

010

96 47

7257

0743

0253

0016

0414

0001

3828

0488

0016

0284

0018

1853

0894

820

Mg-hornblende

rim

47 50

291

920

004

880

014

16 46

11 95

174

008

96 07

6835

1165

0396

0015

0506

0005

3529

0552

0017

0486

0015

1843

0887

825

Mg-hornblende

rim

49 57

269

742

000

799

017

18 07

12 02

133

014

96 88

7013

0987

0261

0018

0575

0000

3811

0371

0020

0365

0026

1821

0860

831

Mg-hornblende

core

47 83

181

872

003

840

011

14 48

12 18

159

008

93 59

6814

1186

0279

0018

0644

0004

3711

0357

0013

0438

0015

1859

0907

874

Pargasite

rim

42 15

249

11 87

024

10 07

013

13 84

11 43

263

032

96 61

6188

1812

0242

0434

0299

0028

3028

0937

0016

0749

0059

1797

0804

972

Pargasite

rim

42 22

260

11 86

026

10 21

011

13 71

11 48

253

032

96 59

6201

1799

0254

0429

0299

0030

3001

0955

0014

0720

0060

1807

0803

962

Pargasite

core

42 05

263

11 45

030

10 19

011

13 80

11 47

246

032

96 46

6189

1811

0175

0478

0299

0035

3029

0956

0014

0702

0060

1809

0767

974

Pargasite

rim

42 36

247

11 90

016

945

013

14 16

11 76

249

026

95 98

6239

1761

0305

0366

0276

0019

3109

0888

0016

0710

0049

1856

0818

926

Pargasite

core

42 50

291

11 64

016

984

015

14 22

11 41

256

034

96 69

6219

1781

0227

0426

0322

0018

3103

0883

0018

0727

0063

1789

0812

974

Pargasite

rim

42 76

270

12 03

017

920

012

14 87

11 82

244

025

96 73

6224

1776

0880

0335

0368

0020

3226

0752

0015

0689

0047

1843

0841

941

Pargasite

rim

42 13

181

13 54

016

921

009

12 77

12 13

254

032

96 98

6172

1828

0510

0450

0000

0018

2788

1129

0011

0721

0059

1905

0841

874

01OA19d

Mg-hornblende

49 26

047

624

011

11 46

017

15 39

12 21

108

009

96 48

7137

0863

0202

0051

0437

0013

3323

0951

0021

0302

0018

1896

0768

771

Mg-hornblende

46 03

287

932

018

906

017

14 77

12 87

193

007

97 28

6672

1328

0265

0313

0046

0021

3191

1053

0021

0542

0012

1999

0758

808

Pargasite

41 89

429

11 65

008

11 03

017

13 52

11 37

259

017

96 77

6159

1841

0179

0474

0345

0010

2963

1012

0021

0739

0032

1791

0770

975

Pargasite

rim

42 80

340

11 16

009

11 01

018

13 73

11 67

240

022

96 67

6293

1707

0226

0376

0322

0010

3009

1032

0022

0684

0041

1839

0605

880

Pargasite

core

42 58

351

11 27

006

11 63

018

13 51

11 46

239

022

96 82

6257

1743

0209

0387

0391

0007

2959

1039

0023

0680

0042

1804

0595

893

Pargasite

rim

42 14

393

11 28

006

11 71

014

13 35

11 33

235

033

96 62

6214

1786

0174

0435

0391

0007

2935

1054

0018

0673

0062

1790

0519

901

Pargasite

core

41 56

420

12 05

006

11 57

016

12 51

11 35

249

027

96 24

6168

1832

0277

0469

0276

0007

2768

1160

0021

0718

0052

1805

0537

882

Pargasite

core

41 33

438

11 49

008

11 66

015

13 35

11 45

264

026

96 80

6105

1894

0107

0487

0368

0009

2941

1073

0019

0757

0048

1813

0537

942

Pargasite

41 08

446

12 39

012

11 35

017

13 13

11 36

263

015

96 85

6049

1951

0199

0494

0368

0014

2882

1030

0021

0752

0027

1792

0758

975

02OA37b

Mg-hornblende

rim

45 15

260

984

002

13 28

019

14 01

10 87

128

009

97 33

6527

1473

0203

0283

0690

0002

3018

0915

0023

0360

0016

1683

0562

828

Mg-hornblende

rim

44 72

263

988

004

13 23

021

14 01

10 78

133

009

96 92

6494

1506

0185

0287

0713

0005

3032

0894

0025

0374

0018

1677

0593

854

Mg-hornblende

rim

45 68

247

935

004

12 87

020

14 10

11 00

121

011

97 02

6621

1379

0218

0269

0598

0004

3045

0962

0024

0341

0020

1708

0562

815

Mg-hornblende

core

43 94

291

10 87

001

12 60

023

13 73

10 59

142

011

96 39

6410

1590

0278

0319

0644

0001

2985

0893

0028

0401

0021

1655

0710

860

Mg-hornblende

core

44 62

270

10 37

001

12 66

019

14 12

10 58

140

008

96 73

6479

1521

0253

0294

0644

0001

3057

0893

0023

0395

0014

1646

0674

851

Mg-hornblende

rim

47 79

181

796

002

12 09

025

15 22

11 09

100

009

97 33

6866

1134

0214

0196

0506

0002

3260

0947

0030

0280

0016

1706

0503

767

Mg-hornblende

core

45 43

249

10 3

000

11 99

022

14 50

11 14

133

008

97 48

6524

1476

0267

0269

0644

0000

3103

0796

0027

0370

0015

1715

0703

838


1194

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein


alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam


Blundythermometer

(1994)Errors

are40

C


1195






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208


Oxygen isotopes


RESULTS











1190




Sam

ple

nam

eSite

Locationin

gab

broic

section

Typ

eofrock

Distance

to

Moho(km)

Parag

enesis

Alteration

87Sr

86Srinitial1

d18O

()2

94MA2

Maq

sad

From

MTZ

Layered

gab

bro

0Olivine(M

gno74---75)3

OPXco

ronas

(Mgno78---79)

WRfrac14

070322

WRfrac14

thorn495

CPX

Palegreen

Am

(cumact)

CPXfrac14

070324

nd

Plagioclase(A


Nolow-T

alteration

Plfrac14

070322

Plfrac14

thorn479

Solidfluid

inclusionsin

Pl

97OA128b

Wad

iWaryiah

From

lower

gab

bro

Layered

gab

bro

1CPX

Low-T

alteration

WRfrac14

070333

nd

Plagioclase(A

n85---87)

Prehnitemicroveins

CPXfrac14

070422

CPXfrac14

thorn523

Plfrac14

070328

Plfrac14

thorn414

01OA41d2

Wad

iGideah

From

upper

gab

bro

Gab

bro

patch

in

laminated

gab

bro

36

CPXrecrystallized


(An57---87)norm

alzoning

Black

pargasitic

honblende

WRfrac14

070351

CPXfrac14

070378

Plfrac14

070426

WRfrac14

thorn480

nd

Plfrac14

thorn504

Hbdfrac14

070355

nd

01OA19aamp

dWad

iWaryiah

Inlayeredgab

bro

Gab

broic

dyke

01

Olivine

OPXpoikilitic

WRfrac14

070341

WRfrac14

thorn567

CPX

Black

pargasite

Hbdfrac14

070324

Hbdfrac14

thorn287

Plagioclase(A

n73---95)


Plfrac14

nd

Plfrac14

thorn10 09

Hem

atite

WRfrac14

070418

nd

Green

Mg-hornblende

Acthornblende

Epidote

02OA90b

Wad

iAl-Abyad

Inlayeredgab

bro

Dioriticdyke

015

Green

Mg-hornblende

Hbdfrac14

070427

Hbdfrac14

thorn239

Plagioclase(A

n83---87)

Plfrac14

070387

Plfrac14

thorn498

Solidfluid

inclusionsin

plagioclase

01OA15f

Wad

iWaryiah

Inlayeredgab

bro

Comb-textured

gab

broic

dyke

025

CPXidiomorphic

Plagioclase(A

n95---99)norm

alzoning

BrownMg-H

ornblende

WRfrac14

070458

nd

02OA43a

Wad

iMayah

Inlayeredgab

bro

vein

Green

amphibole

1Palegreen


Plagioclase(A

n91---97)in

reactionmargin

Hbdfrac14

070431

Hbdfrac14

thorn310

01OA36b

Wad

iGideah

Inlayeredgab

bro

epidosite

dyke

25

CPX

Epidote

WRfrac14

070519

nd

Plagioclase

Epfrac14

070554

nd

CPXclinopyroxene

Plplagioclase

OPXorthopyroxene

Amam

phibolecu

mcu

mmingtonite

actactinolite


Epep

idotend

notdetermined

187Sr


95Ma(H

acker1994)Errors


inTab

le4

2Analyticalerrors

oftheoxygen

isotopevalues

are02

(2s)

3Mgnumber


Fe)

4Percentageofan

orthitein

plagioclase


1191







Blundy (1994)


rim core rim core

01 OA41d2 878 953 ------- -------

01 OA19a 935 974 825 869

01 OA19d 890 933 789 -------

02 OA37b ------- ------- 816 849

02 OA90b ------- ------- 859 833


1192










(wt )



gabb dyke


(margin)

SiO2 4830 4815 4749 4524 4339 4799 389 4371

Al2O3 2785 2032 2438 1474 1246 1192 2752 1646

Fe2O3 328 266 404 981 1204 592 381 623

MnO 003 004 005 014 016 006 008 014

MgO 405 737 427 1031 1686 1326 187 739

CaO 1289 1908 1477 1235 1156 166 2471 2339

Na2O 292 123 257 258 111 075 000 013

K2O 000 000 009 006 000 000 000 000

TiO2 005 017 063 230 064 086 013 042

P2O5 008 007 013 018 009 013 007 010

LOI 033 076 138 216 161 237 274 190

Total 9978 9985 998 9987 9992 9986 9983 9987



1193


aofselectedam

phibolespaired


Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

01OA19a

Mg-hornblende

core

45 60

26

10 78

009

860

015

16 56

12 00

212

007

96 72

6552

1448

0366

0083

0552

0004

3409

0594

0016

0611

0018

1843

0903

899

Mg-hornblende

core

47 99

263

850

002

897

011

16 61

12 10

160

020

96 36

6894

1106

0334

0028

0483

0002

3557

0594

0014

0446

0036

1862

0892

834

Mg-hornblende

rim

51 17

247

596

001

761

014

18 11

12 19

103

010

96 47

7257

0743

0253

0016

0414

0001

3828

0488

0016

0284

0018

1853

0894

820

Mg-hornblende

rim

47 50

291

920

004

880

014

16 46

11 95

174

008

96 07

6835

1165

0396

0015

0506

0005

3529

0552

0017

0486

0015

1843

0887

825

Mg-hornblende

rim

49 57

269

742

000

799

017

18 07

12 02

133

014

96 88

7013

0987

0261

0018

0575

0000

3811

0371

0020

0365

0026

1821

0860

831

Mg-hornblende

core

47 83

181

872

003

840

011

14 48

12 18

159

008

93 59

6814

1186

0279

0018

0644

0004

3711

0357

0013

0438

0015

1859

0907

874

Pargasite

rim

42 15

249

11 87

024

10 07

013

13 84

11 43

263

032

96 61

6188

1812

0242

0434

0299

0028

3028

0937

0016

0749

0059

1797

0804

972

Pargasite

rim

42 22

260

11 86

026

10 21

011

13 71

11 48

253

032

96 59

6201

1799

0254

0429

0299

0030

3001

0955

0014

0720

0060

1807

0803

962

Pargasite

core

42 05

263

11 45

030

10 19

011

13 80

11 47

246

032

96 46

6189

1811

0175

0478

0299

0035

3029

0956

0014

0702

0060

1809

0767

974

Pargasite

rim

42 36

247

11 90

016

945

013

14 16

11 76

249

026

95 98

6239

1761

0305

0366

0276

0019

3109

0888

0016

0710

0049

1856

0818

926

Pargasite

core

42 50

291

11 64

016

984

015

14 22

11 41

256

034

96 69

6219

1781

0227

0426

0322

0018

3103

0883

0018

0727

0063

1789

0812

974

Pargasite

rim

42 76

270

12 03

017

920

012

14 87

11 82

244

025

96 73

6224

1776

0880

0335

0368

0020

3226

0752

0015

0689

0047

1843

0841

941

Pargasite

rim

42 13

181

13 54

016

921

009

12 77

12 13

254

032

96 98

6172

1828

0510

0450

0000

0018

2788

1129

0011

0721

0059

1905

0841

874

01OA19d

Mg-hornblende

49 26

047

624

011

11 46

017

15 39

12 21

108

009

96 48

7137

0863

0202

0051

0437

0013

3323

0951

0021

0302

0018

1896

0768

771

Mg-hornblende

46 03

287

932

018

906

017

14 77

12 87

193

007

97 28

6672

1328

0265

0313

0046

0021

3191

1053

0021

0542

0012

1999

0758

808

Pargasite

41 89

429

11 65

008

11 03

017

13 52

11 37

259

017

96 77

6159

1841

0179

0474

0345

0010

2963

1012

0021

0739

0032

1791

0770

975

Pargasite

rim

42 80

340

11 16

009

11 01

018

13 73

11 67

240

022

96 67

6293

1707

0226

0376

0322

0010

3009

1032

0022

0684

0041

1839

0605

880

Pargasite

core

42 58

351

11 27

006

11 63

018

13 51

11 46

239

022

96 82

6257

1743

0209

0387

0391

0007

2959

1039

0023

0680

0042

1804

0595

893

Pargasite

rim

42 14

393

11 28

006

11 71

014

13 35

11 33

235

033

96 62

6214

1786

0174

0435

0391

0007

2935

1054

0018

0673

0062

1790

0519

901

Pargasite

core

41 56

420

12 05

006

11 57

016

12 51

11 35

249

027

96 24

6168

1832

0277

0469

0276

0007

2768

1160

0021

0718

0052

1805

0537

882

Pargasite

core

41 33

438

11 49

008

11 66

015

13 35

11 45

264

026

96 80

6105

1894

0107

0487

0368

0009

2941

1073

0019

0757

0048

1813

0537

942

Pargasite

41 08

446

12 39

012

11 35

017

13 13

11 36

263

015

96 85

6049

1951

0199

0494

0368

0014

2882

1030

0021

0752

0027

1792

0758

975

02OA37b

Mg-hornblende

rim

45 15

260

984

002

13 28

019

14 01

10 87

128

009

97 33

6527

1473

0203

0283

0690

0002

3018

0915

0023

0360

0016

1683

0562

828

Mg-hornblende

rim

44 72

263

988

004

13 23

021

14 01

10 78

133

009

96 92

6494

1506

0185

0287

0713

0005

3032

0894

0025

0374

0018

1677

0593

854

Mg-hornblende

rim

45 68

247

935

004

12 87

020

14 10

11 00

121

011

97 02

6621

1379

0218

0269

0598

0004

3045

0962

0024

0341

0020

1708

0562

815

Mg-hornblende

core

43 94

291

10 87

001

12 60

023

13 73

10 59

142

011

96 39

6410

1590

0278

0319

0644

0001

2985

0893

0028

0401

0021

1655

0710

860

Mg-hornblende

core

44 62

270

10 37

001

12 66

019

14 12

10 58

140

008

96 73

6479

1521

0253

0294

0644

0001

3057

0893

0023

0395

0014

1646

0674

851

Mg-hornblende

rim

47 79

181

796

002

12 09

025

15 22

11 09

100

009

97 33

6866

1134

0214

0196

0506

0002

3260

0947

0030

0280

0016

1706

0503

767

Mg-hornblende

core

45 43

249

10 3

000

11 99

022

14 50

11 14

133

008

97 48

6524

1476

0267

0269

0644

0000

3103

0796

0027

0370

0015

1715

0703

838


1194

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein


alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam


Blundythermometer

(1994)Errors

are40

C


1195






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208




Sam

ple

nam

eSite

Locationin

gab

broic

section

Typ

eofrock

Distance

to

Moho(km)

Parag

enesis

Alteration

87Sr

86Srinitial1

d18O

()2

94MA2

Maq

sad

From

MTZ

Layered

gab

bro

0Olivine(M

gno74---75)3

OPXco

ronas

(Mgno78---79)

WRfrac14

070322

WRfrac14

thorn495

CPX

Palegreen

Am

(cumact)

CPXfrac14

070324

nd

Plagioclase(A


Nolow-T

alteration

Plfrac14

070322

Plfrac14

thorn479

Solidfluid

inclusionsin

Pl

97OA128b

Wad

iWaryiah

From

lower

gab

bro

Layered

gab

bro

1CPX

Low-T

alteration

WRfrac14

070333

nd

Plagioclase(A

n85---87)

Prehnitemicroveins

CPXfrac14

070422

CPXfrac14

thorn523

Plfrac14

070328

Plfrac14

thorn414

01OA41d2

Wad

iGideah

From

upper

gab

bro

Gab

bro

patch

in

laminated

gab

bro

36

CPXrecrystallized


(An57---87)norm

alzoning

Black

pargasitic

honblende

WRfrac14

070351

CPXfrac14

070378

Plfrac14

070426

WRfrac14

thorn480

nd

Plfrac14

thorn504

Hbdfrac14

070355

nd

01OA19aamp

dWad

iWaryiah

Inlayeredgab

bro

Gab

broic

dyke

01

Olivine

OPXpoikilitic

WRfrac14

070341

WRfrac14

thorn567

CPX

Black

pargasite

Hbdfrac14

070324

Hbdfrac14

thorn287

Plagioclase(A

n73---95)


Plfrac14

nd

Plfrac14

thorn10 09

Hem

atite

WRfrac14

070418

nd

Green

Mg-hornblende

Acthornblende

Epidote

02OA90b

Wad

iAl-Abyad

Inlayeredgab

bro

Dioriticdyke

015

Green

Mg-hornblende

Hbdfrac14

070427

Hbdfrac14

thorn239

Plagioclase(A

n83---87)

Plfrac14

070387

Plfrac14

thorn498

Solidfluid

inclusionsin

plagioclase

01OA15f

Wad

iWaryiah

Inlayeredgab

bro

Comb-textured

gab

broic

dyke

025

CPXidiomorphic

Plagioclase(A

n95---99)norm

alzoning

BrownMg-H

ornblende

WRfrac14

070458

nd

02OA43a

Wad

iMayah

Inlayeredgab

bro

vein

Green

amphibole

1Palegreen


Plagioclase(A

n91---97)in

reactionmargin

Hbdfrac14

070431

Hbdfrac14

thorn310

01OA36b

Wad

iGideah

Inlayeredgab

bro

epidosite

dyke

25

CPX

Epidote

WRfrac14

070519

nd

Plagioclase

Epfrac14

070554

nd

CPXclinopyroxene

Plplagioclase

OPXorthopyroxene

Amam

phibolecu

mcu

mmingtonite

actactinolite


Epep

idotend

notdetermined

187Sr


95Ma(H

acker1994)Errors


inTab

le4

2Analyticalerrors

oftheoxygen

isotopevalues

are02

(2s)

3Mgnumber


Fe)

4Percentageofan

orthitein

plagioclase


1191







Blundy (1994)


rim core rim core

01 OA41d2 878 953 ------- -------

01 OA19a 935 974 825 869

01 OA19d 890 933 789 -------

02 OA37b ------- ------- 816 849

02 OA90b ------- ------- 859 833


1192










(wt )



gabb dyke


(margin)

SiO2 4830 4815 4749 4524 4339 4799 389 4371

Al2O3 2785 2032 2438 1474 1246 1192 2752 1646

Fe2O3 328 266 404 981 1204 592 381 623

MnO 003 004 005 014 016 006 008 014

MgO 405 737 427 1031 1686 1326 187 739

CaO 1289 1908 1477 1235 1156 166 2471 2339

Na2O 292 123 257 258 111 075 000 013

K2O 000 000 009 006 000 000 000 000

TiO2 005 017 063 230 064 086 013 042

P2O5 008 007 013 018 009 013 007 010

LOI 033 076 138 216 161 237 274 190

Total 9978 9985 998 9987 9992 9986 9983 9987



1193


aofselectedam

phibolespaired


Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

01OA19a

Mg-hornblende

core

45 60

26

10 78

009

860

015

16 56

12 00

212

007

96 72

6552

1448

0366

0083

0552

0004

3409

0594

0016

0611

0018

1843

0903

899

Mg-hornblende

core

47 99

263

850

002

897

011

16 61

12 10

160

020

96 36

6894

1106

0334

0028

0483

0002

3557

0594

0014

0446

0036

1862

0892

834

Mg-hornblende

rim

51 17

247

596

001

761

014

18 11

12 19

103

010

96 47

7257

0743

0253

0016

0414

0001

3828

0488

0016

0284

0018

1853

0894

820

Mg-hornblende

rim

47 50

291

920

004

880

014

16 46

11 95

174

008

96 07

6835

1165

0396

0015

0506

0005

3529

0552

0017

0486

0015

1843

0887

825

Mg-hornblende

rim

49 57

269

742

000

799

017

18 07

12 02

133

014

96 88

7013

0987

0261

0018

0575

0000

3811

0371

0020

0365

0026

1821

0860

831

Mg-hornblende

core

47 83

181

872

003

840

011

14 48

12 18

159

008

93 59

6814

1186

0279

0018

0644

0004

3711

0357

0013

0438

0015

1859

0907

874

Pargasite

rim

42 15

249

11 87

024

10 07

013

13 84

11 43

263

032

96 61

6188

1812

0242

0434

0299

0028

3028

0937

0016

0749

0059

1797

0804

972

Pargasite

rim

42 22

260

11 86

026

10 21

011

13 71

11 48

253

032

96 59

6201

1799

0254

0429

0299

0030

3001

0955

0014

0720

0060

1807

0803

962

Pargasite

core

42 05

263

11 45

030

10 19

011

13 80

11 47

246

032

96 46

6189

1811

0175

0478

0299

0035

3029

0956

0014

0702

0060

1809

0767

974

Pargasite

rim

42 36

247

11 90

016

945

013

14 16

11 76

249

026

95 98

6239

1761

0305

0366

0276

0019

3109

0888

0016

0710

0049

1856

0818

926

Pargasite

core

42 50

291

11 64

016

984

015

14 22

11 41

256

034

96 69

6219

1781

0227

0426

0322

0018

3103

0883

0018

0727

0063

1789

0812

974

Pargasite

rim

42 76

270

12 03

017

920

012

14 87

11 82

244

025

96 73

6224

1776

0880

0335

0368

0020

3226

0752

0015

0689

0047

1843

0841

941

Pargasite

rim

42 13

181

13 54

016

921

009

12 77

12 13

254

032

96 98

6172

1828

0510

0450

0000

0018

2788

1129

0011

0721

0059

1905

0841

874

01OA19d

Mg-hornblende

49 26

047

624

011

11 46

017

15 39

12 21

108

009

96 48

7137

0863

0202

0051

0437

0013

3323

0951

0021

0302

0018

1896

0768

771

Mg-hornblende

46 03

287

932

018

906

017

14 77

12 87

193

007

97 28

6672

1328

0265

0313

0046

0021

3191

1053

0021

0542

0012

1999

0758

808

Pargasite

41 89

429

11 65

008

11 03

017

13 52

11 37

259

017

96 77

6159

1841

0179

0474

0345

0010

2963

1012

0021

0739

0032

1791

0770

975

Pargasite

rim

42 80

340

11 16

009

11 01

018

13 73

11 67

240

022

96 67

6293

1707

0226

0376

0322

0010

3009

1032

0022

0684

0041

1839

0605

880

Pargasite

core

42 58

351

11 27

006

11 63

018

13 51

11 46

239

022

96 82

6257

1743

0209

0387

0391

0007

2959

1039

0023

0680

0042

1804

0595

893

Pargasite

rim

42 14

393

11 28

006

11 71

014

13 35

11 33

235

033

96 62

6214

1786

0174

0435

0391

0007

2935

1054

0018

0673

0062

1790

0519

901

Pargasite

core

41 56

420

12 05

006

11 57

016

12 51

11 35

249

027

96 24

6168

1832

0277

0469

0276

0007

2768

1160

0021

0718

0052

1805

0537

882

Pargasite

core

41 33

438

11 49

008

11 66

015

13 35

11 45

264

026

96 80

6105

1894

0107

0487

0368

0009

2941

1073

0019

0757

0048

1813

0537

942

Pargasite

41 08

446

12 39

012

11 35

017

13 13

11 36

263

015

96 85

6049

1951

0199

0494

0368

0014

2882

1030

0021

0752

0027

1792

0758

975

02OA37b

Mg-hornblende

rim

45 15

260

984

002

13 28

019

14 01

10 87

128

009

97 33

6527

1473

0203

0283

0690

0002

3018

0915

0023

0360

0016

1683

0562

828

Mg-hornblende

rim

44 72

263

988

004

13 23

021

14 01

10 78

133

009

96 92

6494

1506

0185

0287

0713

0005

3032

0894

0025

0374

0018

1677

0593

854

Mg-hornblende

rim

45 68

247

935

004

12 87

020

14 10

11 00

121

011

97 02

6621

1379

0218

0269

0598

0004

3045

0962

0024

0341

0020

1708

0562

815

Mg-hornblende

core

43 94

291

10 87

001

12 60

023

13 73

10 59

142

011

96 39

6410

1590

0278

0319

0644

0001

2985

0893

0028

0401

0021

1655

0710

860

Mg-hornblende

core

44 62

270

10 37

001

12 66

019

14 12

10 58

140

008

96 73

6479

1521

0253

0294

0644

0001

3057

0893

0023

0395

0014

1646

0674

851

Mg-hornblende

rim

47 79

181

796

002

12 09

025

15 22

11 09

100

009

97 33

6866

1134

0214

0196

0506

0002

3260

0947

0030

0280

0016

1706

0503

767

Mg-hornblende

core

45 43

249

10 3

000

11 99

022

14 50

11 14

133

008

97 48

6524

1476

0267

0269

0644

0000

3103

0796

0027

0370

0015

1715

0703

838


1194

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein


alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam


Blundythermometer

(1994)Errors

are40

C


1195






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208







Blundy (1994)


rim core rim core

01 OA41d2 878 953 ------- -------

01 OA19a 935 974 825 869

01 OA19d 890 933 789 -------

02 OA37b ------- ------- 816 849

02 OA90b ------- ------- 859 833


1192










(wt )



gabb dyke


(margin)

SiO2 4830 4815 4749 4524 4339 4799 389 4371

Al2O3 2785 2032 2438 1474 1246 1192 2752 1646

Fe2O3 328 266 404 981 1204 592 381 623

MnO 003 004 005 014 016 006 008 014

MgO 405 737 427 1031 1686 1326 187 739

CaO 1289 1908 1477 1235 1156 166 2471 2339

Na2O 292 123 257 258 111 075 000 013

K2O 000 000 009 006 000 000 000 000

TiO2 005 017 063 230 064 086 013 042

P2O5 008 007 013 018 009 013 007 010

LOI 033 076 138 216 161 237 274 190

Total 9978 9985 998 9987 9992 9986 9983 9987



1193


aofselectedam

phibolespaired


Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

01OA19a

Mg-hornblende

core

45 60

26

10 78

009

860

015

16 56

12 00

212

007

96 72

6552

1448

0366

0083

0552

0004

3409

0594

0016

0611

0018

1843

0903

899

Mg-hornblende

core

47 99

263

850

002

897

011

16 61

12 10

160

020

96 36

6894

1106

0334

0028

0483

0002

3557

0594

0014

0446

0036

1862

0892

834

Mg-hornblende

rim

51 17

247

596

001

761

014

18 11

12 19

103

010

96 47

7257

0743

0253

0016

0414

0001

3828

0488

0016

0284

0018

1853

0894

820

Mg-hornblende

rim

47 50

291

920

004

880

014

16 46

11 95

174

008

96 07

6835

1165

0396

0015

0506

0005

3529

0552

0017

0486

0015

1843

0887

825

Mg-hornblende

rim

49 57

269

742

000

799

017

18 07

12 02

133

014

96 88

7013

0987

0261

0018

0575

0000

3811

0371

0020

0365

0026

1821

0860

831

Mg-hornblende

core

47 83

181

872

003

840

011

14 48

12 18

159

008

93 59

6814

1186

0279

0018

0644

0004

3711

0357

0013

0438

0015

1859

0907

874

Pargasite

rim

42 15

249

11 87

024

10 07

013

13 84

11 43

263

032

96 61

6188

1812

0242

0434

0299

0028

3028

0937

0016

0749

0059

1797

0804

972

Pargasite

rim

42 22

260

11 86

026

10 21

011

13 71

11 48

253

032

96 59

6201

1799

0254

0429

0299

0030

3001

0955

0014

0720

0060

1807

0803

962

Pargasite

core

42 05

263

11 45

030

10 19

011

13 80

11 47

246

032

96 46

6189

1811

0175

0478

0299

0035

3029

0956

0014

0702

0060

1809

0767

974

Pargasite

rim

42 36

247

11 90

016

945

013

14 16

11 76

249

026

95 98

6239

1761

0305

0366

0276

0019

3109

0888

0016

0710

0049

1856

0818

926

Pargasite

core

42 50

291

11 64

016

984

015

14 22

11 41

256

034

96 69

6219

1781

0227

0426

0322

0018

3103

0883

0018

0727

0063

1789

0812

974

Pargasite

rim

42 76

270

12 03

017

920

012

14 87

11 82

244

025

96 73

6224

1776

0880

0335

0368

0020

3226

0752

0015

0689

0047

1843

0841

941

Pargasite

rim

42 13

181

13 54

016

921

009

12 77

12 13

254

032

96 98

6172

1828

0510

0450

0000

0018

2788

1129

0011

0721

0059

1905

0841

874

01OA19d

Mg-hornblende

49 26

047

624

011

11 46

017

15 39

12 21

108

009

96 48

7137

0863

0202

0051

0437

0013

3323

0951

0021

0302

0018

1896

0768

771

Mg-hornblende

46 03

287

932

018

906

017

14 77

12 87

193

007

97 28

6672

1328

0265

0313

0046

0021

3191

1053

0021

0542

0012

1999

0758

808

Pargasite

41 89

429

11 65

008

11 03

017

13 52

11 37

259

017

96 77

6159

1841

0179

0474

0345

0010

2963

1012

0021

0739

0032

1791

0770

975

Pargasite

rim

42 80

340

11 16

009

11 01

018

13 73

11 67

240

022

96 67

6293

1707

0226

0376

0322

0010

3009

1032

0022

0684

0041

1839

0605

880

Pargasite

core

42 58

351

11 27

006

11 63

018

13 51

11 46

239

022

96 82

6257

1743

0209

0387

0391

0007

2959

1039

0023

0680

0042

1804

0595

893

Pargasite

rim

42 14

393

11 28

006

11 71

014

13 35

11 33

235

033

96 62

6214

1786

0174

0435

0391

0007

2935

1054

0018

0673

0062

1790

0519

901

Pargasite

core

41 56

420

12 05

006

11 57

016

12 51

11 35

249

027

96 24

6168

1832

0277

0469

0276

0007

2768

1160

0021

0718

0052

1805

0537

882

Pargasite

core

41 33

438

11 49

008

11 66

015

13 35

11 45

264

026

96 80

6105

1894

0107

0487

0368

0009

2941

1073

0019

0757

0048

1813

0537

942

Pargasite

41 08

446

12 39

012

11 35

017

13 13

11 36

263

015

96 85

6049

1951

0199

0494

0368

0014

2882

1030

0021

0752

0027

1792

0758

975

02OA37b

Mg-hornblende

rim

45 15

260

984

002

13 28

019

14 01

10 87

128

009

97 33

6527

1473

0203

0283

0690

0002

3018

0915

0023

0360

0016

1683

0562

828

Mg-hornblende

rim

44 72

263

988

004

13 23

021

14 01

10 78

133

009

96 92

6494

1506

0185

0287

0713

0005

3032

0894

0025

0374

0018

1677

0593

854

Mg-hornblende

rim

45 68

247

935

004

12 87

020

14 10

11 00

121

011

97 02

6621

1379

0218

0269

0598

0004

3045

0962

0024

0341

0020

1708

0562

815

Mg-hornblende

core

43 94

291

10 87

001

12 60

023

13 73

10 59

142

011

96 39

6410

1590

0278

0319

0644

0001

2985

0893

0028

0401

0021

1655

0710

860

Mg-hornblende

core

44 62

270

10 37

001

12 66

019

14 12

10 58

140

008

96 73

6479

1521

0253

0294

0644

0001

3057

0893

0023

0395

0014

1646

0674

851

Mg-hornblende

rim

47 79

181

796

002

12 09

025

15 22

11 09

100

009

97 33

6866

1134

0214

0196

0506

0002

3260

0947

0030

0280

0016

1706

0503

767

Mg-hornblende

core

45 43

249

10 3

000

11 99

022

14 50

11 14

133

008

97 48

6524

1476

0267

0269

0644

0000

3103

0796

0027

0370

0015

1715

0703

838


1194

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein


alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam


Blundythermometer

(1994)Errors

are40

C


1195






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208










(wt )



gabb dyke


(margin)

SiO2 4830 4815 4749 4524 4339 4799 389 4371

Al2O3 2785 2032 2438 1474 1246 1192 2752 1646

Fe2O3 328 266 404 981 1204 592 381 623

MnO 003 004 005 014 016 006 008 014

MgO 405 737 427 1031 1686 1326 187 739

CaO 1289 1908 1477 1235 1156 166 2471 2339

Na2O 292 123 257 258 111 075 000 013

K2O 000 000 009 006 000 000 000 000

TiO2 005 017 063 230 064 086 013 042

P2O5 008 007 013 018 009 013 007 010

LOI 033 076 138 216 161 237 274 190

Total 9978 9985 998 9987 9992 9986 9983 9987



1193


aofselectedam

phibolespaired


Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

01OA19a

Mg-hornblende

core

45 60

26

10 78

009

860

015

16 56

12 00

212

007

96 72

6552

1448

0366

0083

0552

0004

3409

0594

0016

0611

0018

1843

0903

899

Mg-hornblende

core

47 99

263

850

002

897

011

16 61

12 10

160

020

96 36

6894

1106

0334

0028

0483

0002

3557

0594

0014

0446

0036

1862

0892

834

Mg-hornblende

rim

51 17

247

596

001

761

014

18 11

12 19

103

010

96 47

7257

0743

0253

0016

0414

0001

3828

0488

0016

0284

0018

1853

0894

820

Mg-hornblende

rim

47 50

291

920

004

880

014

16 46

11 95

174

008

96 07

6835

1165

0396

0015

0506

0005

3529

0552

0017

0486

0015

1843

0887

825

Mg-hornblende

rim

49 57

269

742

000

799

017

18 07

12 02

133

014

96 88

7013

0987

0261

0018

0575

0000

3811

0371

0020

0365

0026

1821

0860

831

Mg-hornblende

core

47 83

181

872

003

840

011

14 48

12 18

159

008

93 59

6814

1186

0279

0018

0644

0004

3711

0357

0013

0438

0015

1859

0907

874

Pargasite

rim

42 15

249

11 87

024

10 07

013

13 84

11 43

263

032

96 61

6188

1812

0242

0434

0299

0028

3028

0937

0016

0749

0059

1797

0804

972

Pargasite

rim

42 22

260

11 86

026

10 21

011

13 71

11 48

253

032

96 59

6201

1799

0254

0429

0299

0030

3001

0955

0014

0720

0060

1807

0803

962

Pargasite

core

42 05

263

11 45

030

10 19

011

13 80

11 47

246

032

96 46

6189

1811

0175

0478

0299

0035

3029

0956

0014

0702

0060

1809

0767

974

Pargasite

rim

42 36

247

11 90

016

945

013

14 16

11 76

249

026

95 98

6239

1761

0305

0366

0276

0019

3109

0888

0016

0710

0049

1856

0818

926

Pargasite

core

42 50

291

11 64

016

984

015

14 22

11 41

256

034

96 69

6219

1781

0227

0426

0322

0018

3103

0883

0018

0727

0063

1789

0812

974

Pargasite

rim

42 76

270

12 03

017

920

012

14 87

11 82

244

025

96 73

6224

1776

0880

0335

0368

0020

3226

0752

0015

0689

0047

1843

0841

941

Pargasite

rim

42 13

181

13 54

016

921

009

12 77

12 13

254

032

96 98

6172

1828

0510

0450

0000

0018

2788

1129

0011

0721

0059

1905

0841

874

01OA19d

Mg-hornblende

49 26

047

624

011

11 46

017

15 39

12 21

108

009

96 48

7137

0863

0202

0051

0437

0013

3323

0951

0021

0302

0018

1896

0768

771

Mg-hornblende

46 03

287

932

018

906

017

14 77

12 87

193

007

97 28

6672

1328

0265

0313

0046

0021

3191

1053

0021

0542

0012

1999

0758

808

Pargasite

41 89

429

11 65

008

11 03

017

13 52

11 37

259

017

96 77

6159

1841

0179

0474

0345

0010

2963

1012

0021

0739

0032

1791

0770

975

Pargasite

rim

42 80

340

11 16

009

11 01

018

13 73

11 67

240

022

96 67

6293

1707

0226

0376

0322

0010

3009

1032

0022

0684

0041

1839

0605

880

Pargasite

core

42 58

351

11 27

006

11 63

018

13 51

11 46

239

022

96 82

6257

1743

0209

0387

0391

0007

2959

1039

0023

0680

0042

1804

0595

893

Pargasite

rim

42 14

393

11 28

006

11 71

014

13 35

11 33

235

033

96 62

6214

1786

0174

0435

0391

0007

2935

1054

0018

0673

0062

1790

0519

901

Pargasite

core

41 56

420

12 05

006

11 57

016

12 51

11 35

249

027

96 24

6168

1832

0277

0469

0276

0007

2768

1160

0021

0718

0052

1805

0537

882

Pargasite

core

41 33

438

11 49

008

11 66

015

13 35

11 45

264

026

96 80

6105

1894

0107

0487

0368

0009

2941

1073

0019

0757

0048

1813

0537

942

Pargasite

41 08

446

12 39

012

11 35

017

13 13

11 36

263

015

96 85

6049

1951

0199

0494

0368

0014

2882

1030

0021

0752

0027

1792

0758

975

02OA37b

Mg-hornblende

rim

45 15

260

984

002

13 28

019

14 01

10 87

128

009

97 33

6527

1473

0203

0283

0690

0002

3018

0915

0023

0360

0016

1683

0562

828

Mg-hornblende

rim

44 72

263

988

004

13 23

021

14 01

10 78

133

009

96 92

6494

1506

0185

0287

0713

0005

3032

0894

0025

0374

0018

1677

0593

854

Mg-hornblende

rim

45 68

247

935

004

12 87

020

14 10

11 00

121

011

97 02

6621

1379

0218

0269

0598

0004

3045

0962

0024

0341

0020

1708

0562

815

Mg-hornblende

core

43 94

291

10 87

001

12 60

023

13 73

10 59

142

011

96 39

6410

1590

0278

0319

0644

0001

2985

0893

0028

0401

0021

1655

0710

860

Mg-hornblende

core

44 62

270

10 37

001

12 66

019

14 12

10 58

140

008

96 73

6479

1521

0253

0294

0644

0001

3057

0893

0023

0395

0014

1646

0674

851

Mg-hornblende

rim

47 79

181

796

002

12 09

025

15 22

11 09

100

009

97 33

6866

1134

0214

0196

0506

0002

3260

0947

0030

0280

0016

1706

0503

767

Mg-hornblende

core

45 43

249

10 3

000

11 99

022

14 50

11 14

133

008

97 48

6524

1476

0267

0269

0644

0000

3103

0796

0027

0370

0015

1715

0703

838


1194

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein


alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam


Blundythermometer

(1994)Errors

are40

C


1195






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208


aofselectedam

phibolespaired


Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

01OA19a

Mg-hornblende

core

45 60

26

10 78

009

860

015

16 56

12 00

212

007

96 72

6552

1448

0366

0083

0552

0004

3409

0594

0016

0611

0018

1843

0903

899

Mg-hornblende

core

47 99

263

850

002

897

011

16 61

12 10

160

020

96 36

6894

1106

0334

0028

0483

0002

3557

0594

0014

0446

0036

1862

0892

834

Mg-hornblende

rim

51 17

247

596

001

761

014

18 11

12 19

103

010

96 47

7257

0743

0253

0016

0414

0001

3828

0488

0016

0284

0018

1853

0894

820

Mg-hornblende

rim

47 50

291

920

004

880

014

16 46

11 95

174

008

96 07

6835

1165

0396

0015

0506

0005

3529

0552

0017

0486

0015

1843

0887

825

Mg-hornblende

rim

49 57

269

742

000

799

017

18 07

12 02

133

014

96 88

7013

0987

0261

0018

0575

0000

3811

0371

0020

0365

0026

1821

0860

831

Mg-hornblende

core

47 83

181

872

003

840

011

14 48

12 18

159

008

93 59

6814

1186

0279

0018

0644

0004

3711

0357

0013

0438

0015

1859

0907

874

Pargasite

rim

42 15

249

11 87

024

10 07

013

13 84

11 43

263

032

96 61

6188

1812

0242

0434

0299

0028

3028

0937

0016

0749

0059

1797

0804

972

Pargasite

rim

42 22

260

11 86

026

10 21

011

13 71

11 48

253

032

96 59

6201

1799

0254

0429

0299

0030

3001

0955

0014

0720

0060

1807

0803

962

Pargasite

core

42 05

263

11 45

030

10 19

011

13 80

11 47

246

032

96 46

6189

1811

0175

0478

0299

0035

3029

0956

0014

0702

0060

1809

0767

974

Pargasite

rim

42 36

247

11 90

016

945

013

14 16

11 76

249

026

95 98

6239

1761

0305

0366

0276

0019

3109

0888

0016

0710

0049

1856

0818

926

Pargasite

core

42 50

291

11 64

016

984

015

14 22

11 41

256

034

96 69

6219

1781

0227

0426

0322

0018

3103

0883

0018

0727

0063

1789

0812

974

Pargasite

rim

42 76

270

12 03

017

920

012

14 87

11 82

244

025

96 73

6224

1776

0880

0335

0368

0020

3226

0752

0015

0689

0047

1843

0841

941

Pargasite

rim

42 13

181

13 54

016

921

009

12 77

12 13

254

032

96 98

6172

1828

0510

0450

0000

0018

2788

1129

0011

0721

0059

1905

0841

874

01OA19d

Mg-hornblende

49 26

047

624

011

11 46

017

15 39

12 21

108

009

96 48

7137

0863

0202

0051

0437

0013

3323

0951

0021

0302

0018

1896

0768

771

Mg-hornblende

46 03

287

932

018

906

017

14 77

12 87

193

007

97 28

6672

1328

0265

0313

0046

0021

3191

1053

0021

0542

0012

1999

0758

808

Pargasite

41 89

429

11 65

008

11 03

017

13 52

11 37

259

017

96 77

6159

1841

0179

0474

0345

0010

2963

1012

0021

0739

0032

1791

0770

975

Pargasite

rim

42 80

340

11 16

009

11 01

018

13 73

11 67

240

022

96 67

6293

1707

0226

0376

0322

0010

3009

1032

0022

0684

0041

1839

0605

880

Pargasite

core

42 58

351

11 27

006

11 63

018

13 51

11 46

239

022

96 82

6257

1743

0209

0387

0391

0007

2959

1039

0023

0680

0042

1804

0595

893

Pargasite

rim

42 14

393

11 28

006

11 71

014

13 35

11 33

235

033

96 62

6214

1786

0174

0435

0391

0007

2935

1054

0018

0673

0062

1790

0519

901

Pargasite

core

41 56

420

12 05

006

11 57

016

12 51

11 35

249

027

96 24

6168

1832

0277

0469

0276

0007

2768

1160

0021

0718

0052

1805

0537

882

Pargasite

core

41 33

438

11 49

008

11 66

015

13 35

11 45

264

026

96 80

6105

1894

0107

0487

0368

0009

2941

1073

0019

0757

0048

1813

0537

942

Pargasite

41 08

446

12 39

012

11 35

017

13 13

11 36

263

015

96 85

6049

1951

0199

0494

0368

0014

2882

1030

0021

0752

0027

1792

0758

975

02OA37b

Mg-hornblende

rim

45 15

260

984

002

13 28

019

14 01

10 87

128

009

97 33

6527

1473

0203

0283

0690

0002

3018

0915

0023

0360

0016

1683

0562

828

Mg-hornblende

rim

44 72

263

988

004

13 23

021

14 01

10 78

133

009

96 92

6494

1506

0185

0287

0713

0005

3032

0894

0025

0374

0018

1677

0593

854

Mg-hornblende

rim

45 68

247

935

004

12 87

020

14 10

11 00

121

011

97 02

6621

1379

0218

0269

0598

0004

3045

0962

0024

0341

0020

1708

0562

815

Mg-hornblende

core

43 94

291

10 87

001

12 60

023

13 73

10 59

142

011

96 39

6410

1590

0278

0319

0644

0001

2985

0893

0028

0401

0021

1655

0710

860

Mg-hornblende

core

44 62

270

10 37

001

12 66

019

14 12

10 58

140

008

96 73

6479

1521

0253

0294

0644

0001

3057

0893

0023

0395

0014

1646

0674

851

Mg-hornblende

rim

47 79

181

796

002

12 09

025

15 22

11 09

100

009

97 33

6866

1134

0214

0196

0506

0002

3260

0947

0030

0280

0016

1706

0503

767

Mg-hornblende

core

45 43

249

10 3

000

11 99

022

14 50

11 14

133

008

97 48

6524

1476

0267

0269

0644

0000

3103

0796

0027

0370

0015

1715

0703

838


1194

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein


alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam


Blundythermometer

(1994)Errors

are40

C


1195






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208

Sam

ple

nam

e1Mode2

SiO

2TiO

2Al 2O3

Cr 2O3

FeO

MnO

MgO

CaO

Na 2O

K2O

Total

Si

AlIV

AlVI

Ti

Fe3

thornCr

Mg

Fe2

thornMn

Na

KCa

XAn3

T(C)4

02OA90b

Mg-hornblende

core

48 83

038

745

005

939

010

17 29

12 24

142

006

97 21

6931

1069

0041

0041

0667

0005

3657

0448

0011

0392

0010

1862

0840

856

Mg-hornblende

core

49 49

033

731

003

916

008

17 40

12 57

139

005

97 82

6987

1013

0035

0035

0552

0004

3662

0530

0010

0379

0009

1901

0830

811

Mg-hornblende

rim

48 90

040

753

005

932

013

17 15

12 22

154

005

97 29

6948

1052

0042

0042

0575

0006

3632

0533

0015

0424

0010

1861

0880

869

Mg-hornblende

rim

48 30

044

800

007

962

010

16 86

12 32

161

005

97 35

6873

1127

0047

0047

0598

0008

3576

0546

0012

0443

0010

1879

0870

862

Mg-hornblende

rim

49 12

032

742

010

922

011

17 36

12 29

142

006

97 43

6956

1044

0034

0034

0621

0011

3665

0471

0013

0391

0010

1865

0840

845

02OA43a

Mg-hornblende

rim

48 13

040

789

007

860

007

17 41

12 19

155

006

96 36

6882

1118

0212

0043

0621

0008

3710

0407

0008

0429

0010

1867

-------

-------

Mg-hornblende

rim

50 93

035

643

001

759

006

18 50

12 24

114

003

97 28

7152

0848

0217

0037

0506

0001

3873

0385

0007

0311

0005

1841

-------

-------

Mg-hornblende

rim

50 67

014

559

009

12 33

026

15 28

12 44

068

003

97 50

7260

0740

0204

015

0483

0010

3263

0994

0032

0189

0005

1909

-------

-------

Mg-hornblende

rim

50 34

013

621

009

12 49

027

15 07

12 51

064

003

97 78

7192

0810

0240

0010

0530

0010

3210

0960

0030

0180

0010

1910

-------

-------

Mg-hornblende

rim

45 17

060

11 14

013

988

008

15 78

12 33

211

009

97 31

6473

1527

0355

0640

0644

0015

3371

0540

0010

0588

0016

1892

-------

-------

Mg-hornblende

rim

49 25

032

712

014

845

009

17 84

12 32

137

004

96 95

6983

1020

0170

0030

0620

0020

3770

0380

0010

0380

0010

1870

-------

-------

Mg-hornblende

rim

48 61

032

775

014

975

011

16 81

12 57

139

004

97 50

6905

1950

0203

0034

0621

0016

3560

0537

0013

0382

0008

1914

-------

-------

94Ma2

Anthophyllite

54 98

000

259

001

12 65

037

23 35

199

034

000

96 28

7744

0256

0174

0000

0161

0001

4903

1330

0043

0092

0001

0301

-------

-------

Anthophyllite

55 11

000

296

003

14 09

032

23 66

063

038

000

97 18

7716

0284

0205

0000

0115

0003

4938

1535

0038

0104

0000

0095

-------

-------

Actinolite

48 58

004

954

002

960

014

17 67

999

139

005

97 02

6850

0150

0435

0004

0690

0002

3713

0442

0017

0379

0009

1510

-------

-------

Actinolite

51 54

004

585

000

890

022

20 28

930

090

002

97 05

7214

0786

0178

0005

0598

0000

4230

0444

0026

0244

0004

1395

-------

-------

01OA41d2

Pargasite

rim

43 05

342

10 71

008

11 46

012

13 50

11 54

179

067

96 34

6353

1647

0216

0380

0368

0009

2967

1046

0015

0512

0127

1824

0613

863

Pargasite

rim

42 61

354

11 59

001

10 59

010

13 52

11 87

160

076

96 19

6286

1714

0302

0392

0299

0001

2972

1007

0012

0458

0143

1877

0715

844

Pargasite

core

42 54

401

11 04

006

11 81

013

13 21

11 50

202

039

96 71

6266

1734

0182

0444

0368

0007

2901

1087

0017

0576

0073

1814

0854

979

Pargasite

rim

43 03

385

10 72

002

11 70

014

13 50

11 95

146

080

97 17

6314

1686

0168

0425

0345

0002

2953

1091

0018

0415

0149

1878

0634

852

Pargasite

rim

42 65

341

10 60

006

11 97

014

13 22

11 64

183

068

96 20

6332

1668

0186

0381

0345

0007

2926

1141

0018

0528

0129

1851

0620

869

Pargasite

core

42 82

367

10 60

007

11 93

012

13 42

11 44

206

047

96 60

6315

1685

0158

0407

0391

0008

2950

1080

0016

0588

0089

1808

0615

899

Pargasite

rim

42 2

362

11 10

007

11 42

016

13 09

11 72

179

072

95 89

6282

1718

0229

0405

0299

0009

2905

1123

0020

0518

0137

1869

0715

875

Pargasite

rim

42 42

380

11 03

006

11 77

012

13 00

11 72

188

069

96 49

6283

1717

0209

0423

0299

0007

2870

1158

0015

0539

0131

1860

0817

928

Pargasite

rim

42 21

364

11 14

006

10 73

011

13 53

11 68

177

072

95 59

6277

1723

0229

0407

0322

0007

2999

1012

0014

0511

0136

1862

0736

883

Pargasite

rim

42 25

376

11 03

008

10 93

015

13 66

11 72

185

064

96 07

6257

1743

0182

0418

0345

0009

3016

1009

0019

0531

0121

1860

0766

912

Pargasite

core

42 17

396

10 91

008

11 10

010

13 57

11 49

209

038

95 85

6253

1747

0159

0442

0368

0010

3000

1009

0013

0602

0073

1826

0841

981

aMajorelem

entco

mpositionsarein


alysed

andnotemperature

calculated

1Typ

eofam

phibolean

alysed

isalso

indicated

2Blankindicates

nozoningobserved

3Molefractionofan

orthitein

plagioclasead

jacentto

amphibolegrain

4Tem

perature

ofeq

uilibrium

fortheam


Blundythermometer

(1994)Errors

are40

C


1195






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208






GABBROS

01 km 025 km 1 km 36 km50

60

70

80

90

An

MA2

19d

19a 15f 128b

41d2

(a)

43a17b

15f

90b

37b

19a

19d

40

60

80

100

A

n

01 km 015 km 025 km 1 km

DYKES

(b)


ACTINOLITE

MAGNESIOHORNBLENDE

TSCHERMAKITE


19a d37b15f

90b43a

AlIV

150500

02

08

10

(Na

+ K

) A

(c)

04

06

950

900

850

800

750

70007 12 17

T degC

1000

(d)

AlIV



1196


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208


86Srandd1



andveinsfrom

theOman


waterrockratios(W

R)andLOIvalues

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

01OA41d2

Whole

rock

037

1792

0006

0703516

09

070351

thorn480

138

47

0703587

0703651

0703357

Plagioclase

025

1249

0003

0704261

22

070426

thorn504

-------

-------

Pargasite

-------

-------

-------

0703548

20

070355

-------

-------

-------

Clinopyroxene

045

26 0

0050

0703845

19

070378

-------

-------

-------

01OA36b

Dykewhole

rock

0005

7164

50001

0705186

17

070519

-------

274

21 9

0705207

0705112

-------

Epidote

0003

7645

0001

0705536

12

070554

-------

-------

-------

Wallwhole

rock

005

4254

0001

0704637

09

070464

-------

191

-------

0704945

0704675

0704593

02OA43a

Green

hornblende

004

98

0012

0704323

13

070431

thorn310

-------

-------

97OA128b

Whole

rock

003

1274

50001

0703327

17

070333

-------

076

37

-------

-------

-------

Plagioclase

002

1204

50001

0703285

09

070328

thorn414

-------

-------

Clinopyroxene

003

20 0

0004

0704230

09

070422

thorn523

-------

-------

01OA15f

Whole

rock

006

1077

0002

0704582

16

070458

-------

237

13 5

-------

-------

-------

01OA19a

Whole

rock

037

1303

0008

0704189

18

070418

-------

161

96

-------

-------

-------

01OA19d

Whole

rock

058

2032

0008

0703423

08

070341

thorn567

216

415

0703574

0703408

0703271

Pargasite

091

1058

0025

0703273

11

070324

thorn287

-------

-------

Plagioclase

-------

-------

-------

-------

-------

thorn10 09

-------

-------

02OA90b

Plagioclase

004

2385

50001

0703868

11

070387

thorn498

-------

-------

Green

hornblende

010

23 8

0012

0704288

15

070427

thorn239

-------

-------


1197

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208

Table5continued

Sam

ple

Rb(ppm)

Sr(ppm)

87Rb8

6Sr

87Sr

86Sr

(87Sr

86Sr)i1

d18O

()

LOI(

)2WR

3(87Sr

86Sr)L14

(87Sr

86Sr)L25

(87Sr

86Sr)R6

02OA37b

Plagioclase

023

3121

0002

0704204

15

070420

-------

-------

-------

Pargasite

031

41 6

0021

0703505

15

070348

thorn394

-------

-------

94OAMa2

Whole

rock

0016

1750

00003

0703219

15

070322

thorn495

033

31

0703264

0703177

0703158

Plagioclase

0014

1363

00003

0703219

11

070322

thorn479

-------

-------

Clinopyroxene

-------

-------

-------

0703236

13

070324

-------

-------

-------

1Initial8

7Sr


95Ma(H

acker1994)

2LOIisloss

onignition(in)

3Water---rock


TheeffectiveWR

ratiocanbeexpressed

bythefollowingeq

uation

W=Reffectivefrac14

frac12eth87Sr=

86SrrockTHORN fi

nal

eth87Sr=

86SrrockTHORN in

itial=frac12eth8

7Sr=


itial

eth87Sr=

86SrrockTHORN fi

nal

ethCrock

initial=C

seaw

ater

initial

THORNwhere(87Sr


thesample(87Sr

86Srrock) in

itialco

rrespondingto

theinitialm

antlevalue

istakenas

070295(Lan

phere

etal1981)(87Sr

86Srseawater) in


ater

Srisotopicco

mposition[87Sr

86Sr07073

at90

MaafterBurkeet

al(1982)]C

seaw

ater

initial

istheSrco

ntent

oflsquonorm

alrsquoseaw

ater

andis

takenas

8ppm

(deVilliers1999)

FortheCrock

initialitis

assumed

that

thepresentSrco


thesameas

theinitial

concentration




ent(6NHClfor8min

at70

C)



ndstep


ent(2 5NHClfor30

min

at70

C)



dL2leachates


1198


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208


Mineral chemistry

Plagioclase


Amphibole



Thermometry




1199


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208


DISCUSSION







Dykes and veins








1200



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208



-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b

0702 0703 0704 0705 0706 0707

87Sr86Srinitial

MO

RB-s

ou

rce

Seaw

ater


Epidote

(a)

-1000

1000

2000

3000

4000

5000

6000

7000

MOHO

MTZ

Dis

tan

ce a

bov

e th

e M

oh

o (

m)

pillow-basalt

sheeted-dike

gabbro

peridotite

01 OA 41d2

01 OA 36b

02 OA 43a97 OA 128b

01 OA15f

94 OA MA2

02 OA 90b01 OA 19ad

02 OA 37b


3 5 10

δ18O (permil)

41d2

Ma2

43a

90b 19d 19d37b

128b

90b

(b)



1201


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208


Mantle origin









1202





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208





0703

0705

0707

001 01 1

1 Sr (ppm)

MORB

(87Sr

86Sr)

init

ial

Seawater

VHT

HT

MT36b

36b

36b

43a 128b90b

41d2

37b19d

15f

128b

41d2

41d2

19a

Ma2Ma2

19d

90b

37b


Epidote

(a)

0 2 4 6 8

δ18O(permil)

0703

0705

0707Seawater

MORB-mantle

128b 41d2

90b 41d2

Ma2128b

37b

43a

19d

90b


Epidote

HT LT

19d

(87Sr

86Sr)

init

ial

(b)



1203









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208









1204






CONCLUSIONS




1205



ACKNOWLEDGEMENTS






























295---346








1171



173---187






623---634









Research 105 23537---23555





1206











473---489





Program












1563---1569















physics 151 167---197










Monograph 106 267---289

















2777---2782



Research 86(B4) 2709---2720















39---63























151 199---221









1207



2013---2016










499---451




2372






706---708




298 209---217






281 697---734

















49---64






1208

deep and high-temperature hydrothermal circulation in the oman … · 2007. 12. 13. · deep and...

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