northwest africa 773: lunar origin and iron-enrichment trend

Meteoritics amp Planetary Science 38 Nr 4 529ndash554 (2003)Abstract available online at httpmeteoriticsorg

529 copy Meteoritical Society 2003 Printed in USA

Northwest Africa 773 Lunar origin and iron-enrichment trend

T J FAGAN1dagger G J TAYLOR1 K KEIL1 T L HICKS1 M KILLGORE2 T E BUNCH3 J H WITTKE4 DW MITTLEFEHLDT5 R N CLAYTON6 T K MAYEDA6 O EUGSTER7

S LORENZETTI7 and M D NORMAN8

1Hawairsquoi Institute of Geophysics and Planetology School of Ocean and Earth Science and TechnologyUniversity of Hawairsquoi at Manoa Honolulu Hawairsquoi 96822 USA

2PO Box 95 Southwest Meteorite Lab Payson Arizona 85547 USA3Space Sciences Division NASA Ames Research Center Moffett Field California 94035 USA

4Department of Geology Northern Arizona University Flagstaff Arizona 86011 USA5NASA Johnson Space Center Houston Texas 77258 USA

6Enrico Fermi Institute University of Chicago Chicago Illinois 60637 USA7Physikalisches Institut University of Bern 3012 Bern Switzerland

8Research School of Earth Sciences Australian National University Canberra 0200 ACT AustraliadaggerPresent address Tokyo Institute of Technology 2ndash12ndash1 Ookayama Meguroku Tokyo 152ndash8551 Japan

Corresponding author E-mail fagangeotitechacjp

(Received 19 August 2002 revision accepted 9 October 2002)

AbstractndashThe meteorite Northwest Africa 773 (NWA 773) is a lunar sample with implications for theevolution of mafic magmas on the moon A combination of key parameters including whole-rockoxygen isotopic composition FeMn ratios in mafic silicates noble gas concentrations a KREEP-likerare earth element pattern and the presence of regolith agglutinate fragments indicate a lunar originfor NWA 773 Partial maskelynitization of feldspar and occasional twinning of pyroxene areattributed to shock deformation Terrestrial weathering has caused fracturing and precipitation of Ca-rich carbonates and sulfates in the fractures but lunar minerals appear fresh and unoxidized

The meteorite is composed of two distinct lithologies a two-pyroxene olivine gabbro withcumulate texture and a polymict fragmental regolith breccia The olivine gabbro is dominated bycumulate olivine with pigeonite augite and interstitial plagioclase feldspar The breccia consists ofseveral types of clasts but is dominated by clasts from the gabbro and more FeO-rich derivativesVariations in clast mineral assemblage and pyroxene Mg(Mg + Fe) and Ti(Ti + Cr) record anigneous Fe-enrichment trend that culminated in crystallization of fayalite + silica + hedenbergite-bearing symplectites

The Fe-enrichment trend and cumulate textures observed in NWA 773 are similar to features ofterrestrial ponded lava flows and shallow-level mafic intrusives indicating that NWA 773 may befrom a layered mafic intrusion or a thick differentiated lava flow NWA 773 and several other maficlunar meteorites have LREE-enriched patters distinct from Apollo and Luna mare basalts which tendto be LREE-depleted This is somewhat surprising in light of remote sensing data that indicates thatthe Apollo and Luna missions sampled a portion of the moon that was enriched in incompatible heat-producing elements

INTRODUCTION

Igneous rocks from the moon provide invaluable sourcesof information regarding planetary scale differentiation of themoon (Warren 1985 Schmitt 1991 Hess and Parmentier1995 Shearer and Papike 1999) and melting anddifferentiation processes that affected specific lunar rocksuites (Neal and Taylor 1992 Neal et al 1994 Ryder and

Schuraytz 2001) Most of the available lunar igneous rockscome from the Apollo and Luna missions (Warren 1993)Lunar meteorites comprise a much smaller data set than theApollo and Luna samples but the meteorites offset keylimitations of the return mission samples The Apollo andLuna missions are from a limited portion of the moonconcentrated on the lunar maria (Warren and Kallemeyn1991a) The mare basalts from these regions compose nearly

530 T J Fagan et al

one-fifth of the lunar near-side surface but only about 1 ofthe lunar crust (Head and Wilson 1992) Furthermore remotesensing studies show that the Apollo and Luna missionssampled a portion of the moon anomalously enriched inincompatible heat-producing elements (Jolliff et al 2000Lawrence et al 2000) The geochemically anomalous andspatially restricted nature of the areas sampled during theApollo and Luna missions results in a sample set thatalthough extraordinarily valuable cannot be consideredrepresentative of the lunar crust

In light of these limitations lunar meteorites provide animportant complement to the Apollo and Luna samplesObviously interpretation of the lunar meteorites is hinderedbecause we cannot specify a priori the precise location on themoon from which a given meteorite originates Lunarmeteorites may come from anywhere on the moon and thusare not necessarily restricted to a limited region of the near-side With continuing exploration of Antarctica and hotdeserts the number of identified lunar meteorites isincreasing to the point where geochemical patternscharacteristic of meteorites can be discussed and comparedwith systematics of the Apollo and Luna samples (Snyder etal 1999a Warrren and Kallemeyn 1991b Arai et al 2002)

In this paper we describe the lunar meteorite NorthwestAfrica (NWA) 773 document its lunar origin discuss itsimplications for petrogenesis of lunar mafic rocks and comparethis meteorite with geochemical patterns associated withspecific stages of magmatic evolution of the moon (Shearer andPapike 1999) The meteorite consists of two texturally distinctlithologies a dark gray fragmental regolith breccia and agreen two-pyroxene olivine gabbro (Fig 1) We argue that theolivine gabbro and clasts in the breccia record a complexigneous differentiation history The geochemistry of NWA 773is similar in some respects to other mafic lunar meteorites butdistinct from typical Apollo and Luna mare basalts (Snyder etal 1999b Shearer and Papike 1999)

ANALYTICAL METHODS

Petrography and Mineral Compositions

Three polished thin sections of NWA 773 were examinedusing petrographic microscopes Backscattered electron(BSE) images elemental X-ray maps and quantitativeanalyses of phases were collected using a Cameca SX-50electron microprobe at the University of Hawairsquoi and aCameca MBX electron microprobe at Northern ArizonaUniversity Two large-scale elemental maps of Na Mg Al SiP K Ca Ti Cr and Fe Ka were collected using a 15 keV 50nA focused electron beam with step sizes of 9 mm for onethin section and 18 mm for the other section The elementalmaps were combined using image processing software andwere used to estimate mineral modes (Hicks et al 20002002) Modal estimates were based on 13 times 105 counts from

approximately 81 mm2 from one thin section of the brecciaand 43 times 105 counts from 104 mm2 from two thin sections ofthe olivine gabbro Modes and mean mineral compositions(determined by electron microprobe analyses see below)were combined to provide an estimate of major elementalcomposition of the olivine gabbro Compositions of mineralsin the polymict breccia portion of NWA 773 vary over wideranges in different types of clasts thus the elementalcomposition of the breccia was not estimated by modalrecombination

Quantitative mineral compositions were determinedusing wavelength dispersive analyses based on well-characterized oxide and silicate standards A 15 keV voltageand peak and background counting times of 12 to 30 s wereused for all analyses but current and spot size varieddepending on the phase analyzed and the goal of the specificanalyses Most silicates and oxides were analyzed using afocused beam (~1 mm diameter) and 20 nA current Thecurrent was lowered to 10 nA for many feldspar and Ca-phosphate analyses A 10 nA beam rastering over an area ofapproximately 12 times 8 mm was used for analyses of glass inmelt inclusions a glass spherule and a fragment of regolithagglutinate We normalized oxide and silicate mineralformulae assuming that Ti and Cr are present as Ti4+ and Cr3+though we recognize that some Ti3+ and Cr2+ may be present

Bulk Elemental Composition

We initially obtained a small ~200 mg chip of NWA 773dominated by the breccia lithology with a small green clastsimilar to the olivine gabbro for whole-rock geochemicalanalysis We prepared two samples for geochemical analysisfrom this chip We separated an ~14 mg sample of pureolivine-gabbro-like material which we refer to as ldquoclastrdquo andthen ground and homogenized the remaining material as abreccia lithology sample An ~23 mg split of the breccialithology was taken for instrumental neutron activationanalysis (INAA) Subsequent to INAA on these samples wereceived a second ~325 mg chip of the olivine gabbro Thissample was ground and homogenized and an ~39 mg splitwas taken for INAA An ~20 mg split of the homogenizedpowder of the breccia was fused into a glass bead in an Aratmosphere following Brown (1977) for major elementanalysis via electron microprobe (FB-EMPA) A split of theolivine gabbro lithology failed to form a homogeneous glassbeadmdashquench crystals of olivine were ubiquitous on thesurface of the bead Analyses of the fused beads were done onthe JSC SX100 probe Analytical conditions were 15 kV and15 nA with a focused beam rastered over a 10 times 10 mm area

Samples standards and controls were sealed in puresilica glass tubes for INAA The INAA was done in twoirradiations using standard JSC procedures (Mittlefehldt1994) The breccia lithology and the clast sample wereirradiated at a flux of 55 times 1013 n cm-2 s-1 for 20 hr The

Northwest Africa 773 Lunar origin and iron-enrichment trend 531

samples were counted 4 times at roughly 05 1 4 and 8weeks after irradiation to obtain data for nuclides of differinghalf-lives The olivine gabbro lithology sample was irradiatedat a flux of 55 times 1013 n cm-2 s-1 for 16 hr and counted 3 timesat roughly 05 1 and 4 weeks after irradiation

Splits from the ldquoclastrdquo and breccia powders were alsoanalyzed by inductively-coupled plasma mass spectroscopy(ICP-MS) These analyses were completed after themanuscript was submitted for review and the data arepresented in the Appendix The ICP-MS results are consistentwith the INAA data which were submitted with the originalmanuscript for review The ICP-MS data were obtained by

solution aspiration of the dissolved sample into an Agilent7500 quadrupole ICP-MS using a quartz concentric nebulizerand a double pass spray chamber following proceduresdescribed by Norman et al (1998) and Norman andMittlefehldt (2002) Solutions were prepared by dissolving 50mg of sample in HF-HCl-HNO3 The sample was convertedto nitrates and brought up in 50 ml of 5 HNO3 for analysisDistilled reagents were used throughout Beryllium (50 ppb)As (10 ppb) In Re and Bi (5 ppb) were added to eachsolution as internal standards The analyses were calibratedagainst BHVO-1 with USGS reference materials W-2 BIR-1 BCR-2 and AGV-1 used for quality control

Fig 1 a) Photograph of a cut surface of Northwest Africa 773 and b) elemental X-ray map of a thin section with red = Mg Ka green = FeKa and blue = Ca Ka Both images show a sharp boundary dividing breccia matrix (dark gray in [a] Fe-rich composition evident in [b]) fromthe olivine gabbro lithology The olivine gabbro is considered a large lithic fragment in the breccia In the elemental map (b) minerals in theolivine gabbro lithology consist of olivine (yellow) pigeonite (orange) augite (purple) and feldspars (blue) with minor Fe-oxide sulfide andmetal (green) Minor compositions vary more widely in the breccia but the following generalizations hold for the breccia portion of (b) blue= feldspars yellow to yellow-orange = olivine orange = pigeonite green = fayalite or hedenbergite purple = augite black (rare) = silica

532 T J Fagan et al

Bulk Oxygen Isotopes and Noble Gases

A chip and a few fragments of breccia and olivine gabbrowere plucked from a sawed slab with no visible fusion crustand were prepared for oxygen isotopic and noble gasanalyses The oxygen isotopic compositions of the twolithologies of NWA 773 were determined using the methodsof Clayton and Mayeda (1963 1983) The noble gas isotopicabundances were determined from a sample of the olivinegabbro lithology of 184 mg and a sample of the cataclasticbreccia fraction of ~46 mg The breccia sample was crushedin a stainless steel mortar and separated into 3 grain-sizefractions by sieving in acetone 340ndash750 mm (1584 mg) 35ndash340 mm (1501 mg) and lt35 mm (1465 mg) The purpose ofthis separation was to check for enrichment of the surface-correlated trapped solar gases relative to the volume-correlated cosmic ray-produced and radiogenic gases Thesamples were heated in vacuum at 90degC for several days inthe extraction system to remove adsorbed atmospheric gasesHe Ne and Ar were extracted by radiofrequency heating in asingle step at 1700degC and then analyzed in the massspectrometer system B at the University of Bern All detailsconcerning the instrument analytical procedure backgroundand blank corrections have been described in detailpreviously (Eugster et al 1993)

MINERALOGY AND TEXTURES

The meteorite consists of three stones that werepurchased from nomads near Dchira Western Sahara inSeptember 2000 The nomads brought one of us (M Killgore)to the find site and showed the find location of each stone

within an area less than 5 m2 Prior to breakage into splits foranalyses the three stones had masses of 359 g 224 g and50 g and had interlocking surfaces suggesting that they werebroken from a common precursor The 2 larger stones consistof subequal proportions of dark gray fragmental breccia andgreen olivine gabbro The smallest stone consistspredominantly of the olivine gabbro lithology Of the 3 thinsections examined during this study 2 come from the largeststone and one is from the smallest No fusion crust wasidentified in thin section but a very thin crust appears to bepresent in places The external surface of the meteorite isbrown on the breccia lithology and black on the olivinegabbro lithology

The sharp boundary between the olivine gabbro andbreccia lithologies is apparent both on a fresh surface andfrom a thin-section-scale elemental map (Fig 1) whichreflects the higher olivine abundance and Mg(Mg + Fe) ofthe olivine gabbro (Tables 1 2 and 3) No chilled margin orbaked zone is observed along the contact between the olivinegabbro and the breccia In the hand sample green gabbroicfragments similar to the olivine gabbro lithology occur asclasts ranging up to several cm across in the brecciaBoundaries between these clasts and breccia matrix appear tobe identical to the boundary between the olivine gabbro andthe matrix Thus the olivine gabbro was likely simply alarge clast in the breccia and NWA 773 was broken along theinterior of the clast

Terrestrial weathering has resulted in the fracturing ofmost grains larger than about 100 mm across (Fig 2) and manyof the fractures are filled with Ca-carbonates and sulfatesExcept for fracturing and precipitation in the fractures lunarminerals in the meteorite show minimal alteration no hydrous

Fig 2 Backscattered electron images of the NWA 773 olivine gabbro lithology a) large cumulate olivine (olv) with adjacent pigeonite (pig)and plagioclase feldspar (fsp) The BSE-bright grain along the boundary of olivine and feldspar is Cr-spinel Two rounded pyroxene-phyric meltinclusions are trapped within the large olivine grain The weathering veins are black in this image and are dominated by voids and Ca-richcarbonate b) residual pocket of phases enriched in incompatible elements Mineral abbreviations kfs = K Ba-feldspar cph = Ca-phosphatesilm = ilmenite tr = troilite fsp = plagioclase feldspar cpx = augite The asterisk marks the location of the An-poor analysis (An75) in Table 5


alteration of lunar minerals was observed metal troilite andFe Ti-oxides appear free of rust in the thin section unfracturedgrain boundaries appear sharp and free of hydrous alteration orrust the rock is well-indurated

Olivine Gabbro Lithology

The olivine gabbro appears light green on a fresh surfacebecause of the abundance of coarse-grained olivine andpyroxenes (Fig 1) Our modal estimate (Table 1) indicatesthat this portion of NWA 773 should be classified as a two-pyroxene olivine gabbro A more olivine-rich compositionfrom another specimen of NWA 773 has been classified asfeldspathic lherzolite (Bridges et al 2002)

Olivine crystals are equant to slightly elongate euhedralto subhedral grains forming a loose aggregate characteristicof cumulate rocks Olivine occupies approximately 55 volof this lithology (Table 1) and individual crystals range up to1300 mm across in the thin section (Fig 2a) Undulatoryextinction is characteristic indicating deformation of thecrystal lattice Olivine compositions in the olivine gabbrovary over a limited range near Fo68 (Table 2 Fig 3) All of the120 analyses collected at the University of Hawairsquoi in thislithology yield compositions ranging between Fo66 and Fo72with a mean of Fo68 The individual olivine crystals appear tobe unzoned The ratios of FeMn are comparable to lunarolivines (Fig 3)

Two types of melt inclusions are trapped within theolivine crystals One type is characterized by fine-graineddendritic pyroxene in a glass matrix (Fig 2a) and is broadlyandesitic in composition with a mean SiO2 concentration of61 wt (Table 3) In some cases branches of dendriticpyroxene appear to radiate from common nucleation points inthe melt inclusions The other type of melt inclusion is muchmore silicic (Table 3) and is devoid of dendritic pyroxeneThese silica-rich inclusions are generally aphyric but in somecases 1 or 2 Ca-phosphate crystals may be present Multiplemelt inclusions of the same type are found in the same crystal(Fig 2a) but both types of inclusions have not been identifiedtogether in a single olivine host

Olivine crystals in the olivine gabbro are in contact withand in some cases rimmed by subhedral pigeonite Pigeonitein turn occurs in contact with and may be rimmed by augite

Pigeonite is more abundant (Table 1) and tends to be coarser-grained than augite but both types of pyroxene range up to1000 mm across Pyroxene crystals are equant with anhedralto subhedral form No exsolution lamellae were identified inour samples at the spatial resolution of SEM and EPMAobservations However 1-mm-scale lamellae in anotherspecimen of NWA 773 have been reported by Korotev et al(2002) Twin lamellae were identified in some of thepigeonite and all of the pyroxene exhibits undulatoryextinction indicating that NWA 773 was deformed aftercrystallization Pyroxenes in the olivine gabbro have limitedcompositional ranges near Wo11En65 and Wo36En50 and areseparated by a well-defined compositional gap (Table 4 Fig4) Mineral normalizations of EPMA data suggest that all theFe is ferrous unlike pyroxene from terrestrial mafic rocksRatios of FeMn in the pyroxene from the olivine gabbro areconsistent with a lunar or terrestrial origin (Fig 3) but theapparent absence of ferric iron indicates a non-terrestrialorigin

Aluminum Ti and Cr occur in the pyroxenes in minorconcentrations (Table 4) Most analyses of pyroxene from theolivine gabbro have TiAl = 025 and all results yield TiAllt05 (Fig 5) Analyses with relatively high TiAl also tend tohave high Ti(Ti + Cr) consistent with late-stagecrystallization in a system that fractionated compatible Cr andincompatible Ti Higher Ti(Ti + Cr) in pyroxene correlateswith more Fe-rich compositions but the variation in Fe

Table 1 Modal abundances of NWA 773Olivine gabbro Breccia

Olivine 555 21Pigeonite 189 39Augite 87 17Plagioclase 142 19K Ba feldspar 16 25Chromite 09 03Fe Ti oxides 03 01Silica 0 08Ca phosphate lt02 02

Table 2 Representative electron microprobe analyses (wt) of olivines from NWA 773

Olivine Gabbro Breccia

Clast type (breccia) Gabbro

Fe-rich lithic Symplectite

SiO2 372 359 292 296TiO2 lt003 006 013 012Al2O3 lt002 003 lt002 lt002Cr2O3 007 009 005 lt004FeO 285 336 683 644MnO 027 029 076 063MgO 338 299 094 423CaO 024 034 046 031Total 1002 1001 998 994

Structural formulae based on 4O

Si 0996 0988 0987 0984Ti bda 0001 0003 0003Al bd 0001 bd bdCr 0001 0002 0001 bdFe 0639 0774 193 179Mn 0006 0007 0022 0018Mg 135 123 0047 0209Ca 0007 0010 0017 0011Total 300 301 301 301Fo 68 61 2 10

abd = below detection

534 T J Fagan et al

Fig 3 Concentrations of Fe and Mn in olivine and pyroxene from NWA 773 The atoms per formula unit is based on 4 oxygen for olivine and6 oxygen for pyroxene The ratios of FeMn associated with specific parent bodies are from Papike (1998)

Table 3 Mean (plusmn1s and minimum ndash maximum) results of analyses of glassy phases in Northwest Africa 773

Yellow-green spherulen = 22

Agglutinate glassn = 12

Pyroxene phyric melt inclusions in olivinen = 66

Aphyric melt inclusions in olivinen = 16

SiO2 433 plusmn 03 440 plusmn 02 612 plusmn 38 791 plusmn 51427 - 438 436 - 445 548 - 699 708 - 870

TiO2 142 plusmn 005 019 plusmn 007 22 plusmn 05 039 plusmn 025133 - 152 010 - 035 12 - 32 022 - 129

Al2O3 150 plusmn 01 324 plusmn 05 143 plusmn 08 89 plusmn 20148 - 152 313 - 330 124 - 161 58 - 123

Cr2O3 029 plusmn 004 lt007 lt007 lt007021 - 037 lt007 - 010 lt007 - 018 lt007 - 008

FeO 156 plusmn 03 28 plusmn 04 45 plusmn 17 15 plusmn 14152 - 164 21 - 34 13 - 78 08 - 66

MnO 022 plusmn 003 lt006 007 plusmn 004 lt006016 - 028 lt006 - 008 lt006 - 014 lt006 - 007

MgO 111 plusmn 01 208 plusmn 015 20 plusmn 06 057 plusmn 151109 - 113 186 - 235 06 - 36 lt002 - 62

CaO 116 plusmn 01 178 plusmn 03 132 plusmn 18 32 plusmn 27113 - 117 171 - 181 89 - 160 11 - 102

Na2O 003 plusmn 001 036 plusmn 003 077 plusmn 026 10 plusmn 07lt003 - 006 032 - 041 037 - 177 04 - 24

K2O lt003 003 plusmn 002 016 plusmn 007 31 plusmn 24lt003 - 004 lt003 - 006 004 - 043 04 - 71

P2O5 lt006 lt006 034 plusmn 010 lt006lt006 - 007 lt006 - 008 014 - 060 lt006 - 34

Total 986 plusmn 05 997 plusmn 03 988 plusmn 05 982 plusmn 06978 - 996 990 - 1001 973 - 998 973 - 993


Table 4 Representative electron microprobe analyses (wt) of pyroxenes from NWA 773Olivine gabbro Breccia

Pyroxene Pigeonite Augite Pigeonite Pig-Auga Augite Hedenbergite Hedenbergite Pigeonite Augite Pigeonite Augiteclast type (breccia)

single mineral

single mineral gabbro

fayalite gabbro symplectite

zoned pyx

zoned pyx basalt basalt

SiO2 528 524 530 499 518 460 451 500 503 518 486TiO2 040 022 015 034 031 103 137 037 039 067 146Al2O3 150 168 098 114 241 108 143 132 220 185 397Cr2O3 062 077 055 025 108 006 lt004 059 104 124 161FeO 156 840 190 255 875 305 3196 2387 136 1746 142MnO 025 022 034 038 023 033 037 042 027 025 028MgO 233 179 225 131 178 158 124 147 151 223 151CaO 560 175 323 886 170 181 168 850 163 383 139Na2O lt002 004 lt002 lt002 003 003 lt002 lt002 003 lt002 lt002Total 1001 991 997 995 994 993 984 997 992 994 991


Si 194 194 197 195 192 193 191 194 191 192 185ivAl 0064 0055 0035 0046 0080 0053 0071 0060 0089 0076 0153Total tetb 200 200 200 200 200 198 198 200 200 200 200Ti 0011 0006 0004 0010 0009 0033 0044 0011 0011 0019 0042viAl 0065 0074 0043 0053 0105 0053 0071 0060 0098 0081 0178Cr 0018 0022 0016 0008 0032 0002 bdc 0018 0031 0036 0048Fe 0477 0261 0589 0834 0271 1068 1131 0773 0430 0542 0450Mn 0008 0007 0011 0013 0007 0012 0013 0014 0009 0008 0009Mg 1275 0990 1244 0764 0983 0099 0078 0847 0855 1236 0857Ca 0220 0696 0129 0371 0675 0811 0762 0353 0664 0153 0567Na bd 0003 bd bd 0002 bd bd bd 0002 bd bdTotal 401 400 400 401 400 401 401 401 401 400 400Wo 11 36 7 19 35 41 39 18 34 8 30En 65 51 63 39 51 5 4 43 44 64 46

aldquoPig-Augrdquo refers to pyroxenes with Wo~20bTotal tet = total of tetrahedral cationscbd = below detection

Fig 4 Quadrilateral compositions of pyroxenes from NWA 773 Note the well-defined separation of low- and high-Ca pyroxenes in the olivinegabbro lithology

536 T J Fagan et al

content is very slight with Mg(Mg + Fe) from ~076 to 072(see Fig 5) The analysis with Ti(Ti + Cr) ~087 is actuallydepleted in high field strength elements and constitutes aspecial case as it is from a rare equant pyroxene trapped in amelt inclusion in olivine The other analyses with high Ti(Ti+ Cr) have relatively high Ti concentrations (gt015 atoms performula unit) and were determined in domains close toincompatible-element-rich residual melt pockets (see below)

Feldspars are anhedral conforming to crystal margins ofolivine and pyroxene and occupy only 14 vol of the olivinegabbro lithology in comparison to approximately 80 volmafic silicates (Table 1) In general the feldspars aremaskelynitized but some feldspar domains exhibitbirefringence Plagioclase is by far the more abundantfeldspar (Table 1) and occurs as relatively inclusion-freecrystals up to several hundred mm across In contrast mostalkali feldspar crystals are 50 to 100 mm across with somecrystals ranging up to 300 mm long and are characterized bymultiple inclusions of Ca-phosphates ilmenite and troilite(Fig 2b) These minerals occur as inclusions entirely withinalkali feldspar along grain boundaries and as inclusionsclustered within 100 mm of alkali feldspar but hosted inadjacent pyroxene or plagioclase (Fig 2b)

Most analyses of plagioclase in the olivine gabbrolithology indicate compositions near An90Ab10 (Table 5)However plagioclase in close proximity to alkali feldspar has

higher alkali contents (Table 5 An as low as An75 Or as highas Or09) Alkali feldspar is cathodoluminescent and isenriched in Ba as well as K (Table 5) During initial exposureto the electron beam the K Ba-feldspar luminesces a brightwhite or blue and luminescence fades during exposure to thebeam over the course of an analysis (15 min) Bariumconcentrations from 32 analyses of K Ba-feldspar in theolivine gabbro range from 079ndash360 wt BaO with a meanof 22 wt (mean celsian content Cs04)

The K Ba-feldspar crystals together with associatedsplays of fine Ca-phosphates ilmenite and troilite compriseincompatible-element-rich residual pockets enclosed withinthe framework of mafic silicates (Fig 2b) Grains of Fe Ni-metal also occur in the residual pockets but are rare Ilmeniteand Ca-phosphates occur as elongate prisms typically on theorder of 50 to 100 mm in length while troilite grains tend to beequant and under 30 mm across Significant MgO is present inthe ilmenite (Table 6) similar to many lunar ilmenites TheCa-phosphate prisms frequently consist of both apatite andwhitlockite separated by a curved or irregular boundary Thehigh F contents of apatite (Table 7) are similar to apatitesfrom the moon

Chromian spinel occurs as equant euhedral grains on theorder of 100 mm across included in pyroxene and alongpyroxene-olivine grain boundaries In some cases Cr-spinelconforms to the crystal outlines of adjacent olivine rare Cr-

Fig 5 Main ldquooff-quadrilateralrdquo components of pyroxenes from NWA 773 a) Ti versus Al in atoms per 6 oxygen formula unit b) Ti versusMg with Mg reversed so that crystal fractionation drives compositions away from the origin on both axes (see Arai et al 1996) Note theTi Cr-rich compositions of pyroxene from the basaltic clast shown in Fig 6d


spinel grains are included in olivine The Cr-spinel is a solidsolution with significant TiO2 and MgO and yieldsstoichiometric compositions with all Fe assumed to be ferrous(Table 6)

Breccia Lithology

The breccia matrix appears dark gray to black on a freshsurface but coarse clasts in the breccia exhibit a variety ofshades of green and gray (Fig 1) The breccia consists of avariety of types of fragments many similar or plausiblylinked to the adjacent olivine gabbro lithology In spite of thesimilarities modal abundances of the two lithologies clearlydiffer The breccia has lower modal olivine and higherabundances of plagioclase feldspar and pyroxenes (Table 1Fig 1)

The breccia has a fragmental texture with a continuum ingrain size from fine matrix grains (~5 mm) to coarse clasts(gt1000 mm) Unlike many of the fragmental brecciascollected during Apollo missions the NWA 773 breccia iswell-indurated and has minimal porosity The breccia is

polymict and the matrix appears to consist of fragmentssimilar in lithology to the breccia clasts but broken into finergrain sizes No whole-rock shock-melt glass was identifiedHowever mineral grains show clear signs of shockdeformation including maskelynitization of feldspar andundulatory extinction in olivine and pyroxene similar todeformation of the olivine gabbro lithology Theseobservations are not repeated in the clast type descriptionsthat follow

The description below is organized according to clasttype This description is representative but not exhaustiveand focuses on the largest and most abundant clast typesidentified in the breccia

GabbroGabbroic clasts are characterized by coarse interlocking

(ldquoplutonicrdquo) textures plagioclase feldspar with compositionsranging between An80 and An96 and mafic silicates with Mg(Mg + Fe) gt02 but no higher than Mg(Mg + Fe) valuesdetermined in the olivine gabbro lithology (Tables 2 4 and5) Most clasts that are considered ldquogabbroicrdquo do not have the

Table 5 Representative electron microprobe analyses (wt) of feldspars and silica-rich glass from NWA 773Olivine gabbro Breccia

PhasePlagio-clasea

Plagio-claseb

K Ba feldspar

Plagio-clase

Plagio-clase

K Ba feldspar

Plagio-clase

Silica-rich glass

Silica-rich glass

Silica-rich glass

Silica-rich glass

clast type (breccia) gabbro gabbro gabbro

symplec-tite mineral

fayalite granite

symplec-tite

symplec-tite

SiO2 4587 4954 6275 4637 5051 6159 5067 9680 9922 9723 7778TiO2 lt005 008 022 lt005 lt005 031 lt005 033 025 017 012Al2O3 3474 3213 1951 3403 3106 2006 3091 037 067 059 1269FeO 030 033 lt007 049 088 033 111 075 015 109 108MgO 017 017 lt002 027 lt002 lt002 lt002 lt002 lt002 lt002 lt002CaO 1795 1500 040 1797 1441 089 1401 005 lt004 011 021Na2O 105 179 042 101 267 058 258 lt004 018 lt004 030K2O 014 138 1510 011 051 1419 058 022 024 014 459BaO nac 013 197 lt006 011 221 na na na na naTotal 1003 1005 1004 1003 1002 1002 999 985 1007 994 968

Structural formulae based on 8O (feldspars) and 2O (silica-rich glass)

Si 211 226 293 213 231 288 232 0990 0990 0987 0852Al 188 173 107 184 167 111 167 0005 0008 0007 0164Total tetd 399 399 399 397 398 399 399 099 100 099 102Ti bde 0003 0008 bd bd 0011 bd 0003 0002 0001 0001Fe 0012 0013 bd 0019 0034 0013 0043 0006 0001 0009 0010Mg 0012 0012 bd 0018 bd bd bd bd bd bd bdCa 0884 0734 0020 0885 0705 0045 0687 0001 bd 0001 0003Na 0094 0159 0038 0090 0237 0053 0229 bd 0003 bd 0006K 0009 0080 0898 0007 0030 0848 0034 0003 0003 0002 0064Ba na 0002 0036 bd 0002 0041 na na na na naTotal 500 499 500 499 499 500 498 101 101 101 110An 90 75 2 90 73 5 72 ndash ndash ndash ndashAb 10 16 4 9 24 5 24 ndash ndash ndash ndashOr 1 8 90 1 3 86 4 ndash ndash ndash ndashCs na 0 4 0 0 4 na ndash ndash ndash ndash

aAnalysis from most common petrographic setting for plagioclase interstitial to pyroxenes and olivines and not in close proximity to K-feldsparbAnalysis located in close proximity to adjacent K-feldspar crystal (150 mm see Fig 3b)cna = not analyzeddTotal tet = Total tetrahedral cationsebd = below detection

538 T J Fagan et al

full suite of major silicate minerals observed in the olivinegabbro lithology namely olivine pigeonite augite andplagioclase feldspar However many polymineralic gabbroicclasts have textures similar to those observed in the olivinegabbro olivine appears to be rimmed by pigeonite pigeoniteand augite occur together along interlocking grain boundarieswith no exsolution lamellae observed in pigeonite sphericalandesitic melt inclusions with dendritic pyroxene are presentin some coarse olivine crystals and interstitial K Ba-feldsparcrystals occur in some polycrystalline clasts The grain sizesof the mafic silicates are comparable to those in the olivinegabbro but do not range up to the coarsest sizes observed inthe olivine gabbro lithology Plagioclase feldspar grains in thegabbroic clasts are as coarse or coarser (up to ~1000 mmacross see Fig 1) than their counterparts in the olivinegabbro lithology Many coarse single-mineral fragments aresimilar in composition grain size and grain shape to thepolycrystalline gabbroic clasts and probably share a similarorigin

Olivine in gabbroic clasts in the breccia are broadlysimilar in composition to olivine from the olivine gabbrolithology but range to somewhat more Fe-rich compositions(minimum of Fo55 compared to a minimum of Fo66 in theolivine gabbro see Fig 3) In contrast gabbroic pyroxenefrom the breccia exhibits a much wider range in compositionthan pyroxene from the olivine gabbro lithology As is thecase for olivine some analyses of pyroxene from gabbroic

clasts duplicate results from the olivine gabbro howeverseveral analyses of gabbroic pyroxene from the breccia showa trend toward much higher FeMg (maximum of Fs60 fromthe breccia maximum of Fs33 from the olivine gabbrolithology) The trend toward higher FeMg is accompanied bya shift toward Ca-contents near Wo20 intermediate betweenthe high-Ca augite and low-Ca pigeonite compositionscharacteristic of the olivine gabbro (Fig 4) Pyroxene with

Table 6 Representative electron microprobe analyses (wt) of oxides from NWA 773

Olivine gabbro BrecciaMineral Cr-spinel Ilmenite Ulvouml-spinel Ilmeniteclast type (breccia) gabbro gabbro

TiO2 118 557 299 524Al2O3 883 lt002 260 003Cr2O3 347 058 627 030FeO 386 388 598 459MnO 030 037 028 031MgO 432 525 058 065CaO 006 lt002 008 008SiO2 015 018 019 011Total 987 1008 997 997

Structural formulae based on

4O 3O 4O 3OTi 0311 1002 0828 0992Al 0366 bda 0113 0001Cr 0964 0011 0183 0006Fe 1135 0776 184 0966Mn 0009 0007 0009 0007Mg 0226 0187 0032 0024Ca 0002 bd 0003 0002Si 0005 0004 0007 0003Total 302 199 302 200


Table 7 Representative electron microprobe analyses (wt) of Ca-phosphates from NWA 773

Olivine gabbro Breccia

Mineral Whitlockitea Apatiteb Apatitea Apatitea

clast type (breccia) symplectite symplectite

CaO 417 533 543 547P2O5 417 415 413 406FeO 076 068 056 046MgO 261 011 lt002 lt002Na2O 037 nac lt003 lt003K2O 005 na lt003 lt003SiO2 084 054 033 039Al2O3 043 007 lt003 lt003SrO 005 na 008 010La2O3 084 na lt005 lt005Ce2O3 240 na 003 02SO3 005 na 005 005Cl lt004 016 013 02F 375 382 360 375Total 956 1002 1007 1005Nd2O3

d 25 na na naTotal 981 1002 1007 1005O == Cl F 158 164 155 162Total 965 986 991 988


8O 125O 125O 125OCa 249 486 495 502P 197 299 297 294Fe 0035 0048 0040 0033Mg 0217 0014 bde bdNa 0040 na bd bdK 0002 na bd bdSi 0047 0046 0028 0033Al 0028 0007 bd bdSr 0002 na 0004 0005La 0017 na bd bdCe 0049 na 0009 0006S 0002 na 0003 0003Nd 0050 na na naCations 495 797 800 804Cl bd 0022 0019 0029F 0661 1027 0968 1015

aAnalysis from University of Northern ArizonabAnalysis from University of Hawairsquoi at Manoacna = not analyzeddNd2O3 estimated from energy dispersive spectrumebd = below detection


higher FeMg also tends to be enriched in Ti and depleted inCr (Fig 5) Analyses of plagioclase from the gabbroic clastsrange in composition from An96 to An80 covering the samerange as plagioclase distant from and proximal to residualpockets in the olivine gabbro lithology (Table 5)

Fe-Rich Lithic Clasts Fayalite-Bearing Gabbroic and Granitic Rocks

Fayalitic olivine K Ba-feldspar and minor whitlockiteand apatite are characteristic of the Fe-rich lithic clasts in thebreccia (Tables 2 5 and 7) Hedenbergite silica plagioclasefeldspar troilite and baddeleyite may also be present Thelargest most abundant Fe-rich lithic clasts are composedmostly (gt60) of hedenbergite and fayalite and are referredto here as fayalite gabbros (Fig 6a) they are unusual gabbroshowever in that the dominant feldspar is K Ba-feldsparOther Fe-rich lithic clasts have abundant (gt60) silica +

feldspars minimal hedenbergite and significant plagioclaseas well as alkali feldspar (Fig 6b) and are referred to here asfayalite granites Abundances of silica plagioclase and alkalifeldspar vary beyond granitic ratios sensu stricto but theclasts are broadly granitic in composition in that they areenriched in silica and feldspars

In spite of the range of modal abundances from gabbroicto granitic rocks mineral textures and compositions in the Fe-rich lithic clasts are similar in many respects Hedenbergiteand fayalite tend to have equant to prismatic subhedralcrystal form with crystal sizes ranging up to several hundredmicrometers across (Figs 6a and 6b) The K Ba-feldspar isfiner-grained and interstitial to mafic silicates in gabbroicclasts in granitic clasts feldspars are intergrown with thinblades of silica (Fig 6b) Silica in the Fe-rich lithic clastsoften has a prismatic shape but appears to be isotropicWhether or not the isotropic structure of silica is original or a

Fig 6 Backscattered electron images from NWA 773 breccia lithology a) Fe-rich lithic gabbroic clast b) Fe-rich lithic granitic clast c)symplectite d) clast of pyroxene phyric basalt Mineral abbreviations bad = baddeleyite cph = Ca-phosphate fa = fayalite fsp = plagioclasefeldspar hd = hedenbergite kfs = K Ba-feldspar sil = silica glass tr = troilite The dark gray phase with hedenbergite and fayalite insymplectite (c) is silica

540 T J Fagan et al

consequence of shock deformation is not known Wherepresent plagioclase feldspar has equant or tabularmorphologies and occurs in crystals on the order of 100 mmacross Ca-phosphates are fine-grained with prismatic oranhedral form and in the fayalite granites occur as very fine-grained anhedral crystals interstitial to the bladedintergrowths of K Ba-feldspar and silica (Fig 6b)

The fayalitic composition of olivine in the Fe-rich lithicclasts constitutes a discontinuous break from the more Mg-rich compositions of olivines from the olivine gabbrolithology and from gabbroic fragments in the breccia (Fig 3)The hedenbergitic pyroxene is much more Fe-rich than augiteand pigeonite characteristic of the olivine gabbro and themost Mg-rich gabbroic clasts in the breccia However severalanalyses of gabbroic pyroxene have intermediate FeMg andTiCr ratios (Figs 4 5) Compositions of feldspars from theFe-rich lithic clasts fall in the same range as those fromgabbroic clasts and the olivine gabbro lithology but onaverage are more enriched in alkalis All 7 analyses ofplagioclase from the Fe-rich lithic clasts fall between An72

and An75 compositions enriched in albite compared toplagioclase from the olivine gabbro and the gabbroic clastsThe K Ba-feldspar in Fe-rich lithic clasts ranges to higher Bacontents (Cs13) than the olivine gabbro K Ba-feldspar

SymplectiteSymplectic clasts are composed of silicates similar to the

Fe-rich lithic clasts but with abundant fine-grainedintergrowths of symplectic hedenbergite fayalite and silica-rich phases (Fig 6c) The symplectite is characterized byfine-grained worm-like intergrowths of fayalite andhedenbergite with silica-rich glass or feldspar plusmn Fe Ti-oxideMassive (ldquononsymplecticrdquo) domains of fayalite andhedenbergite occur in the same clasts adjacent to symplecticdomains In addition to these phases coarse-grained equantapatite and euhedral plagioclase feldspar are present in somesymplectic clasts This occurrence of plagioclase has acomposition near An70ndash75 similar to plagioclase from the Fe-rich lithic clasts and plagioclase adjacent to the incompatible-element-rich residual pockets in the olivine gabbro lithology(Table 5) A transitional symplectite texture is present in somehedenbergitic pyroxene crystals which host multipleclosely-spaced spherical to irregularly shaped inclusions offayalite and a silica-rich phase plusmn Fe Ti-oxide (Fig 6c)

Symplectic olivine is fayalitic similar in composition toolivine from the Fe-rich lithic clasts but with a rangeextending to lower FeMg (Table 2 Fig 3) Likewisesymplectic pyroxene is generally similar in composition tohedenbergite from the Fe-rich lithic clasts but with a rangeextending to lower FeMg and TiMg ratios (Table 4 Figs 4and 5) Analyses of the silica-rich phase intergrown withsymplectic fayalite and hedenbergite yield results rangingfrom nearly stoichiometric silica to non-stoichiometricAl2O3- and K2O-bearing compositions (Table 5) Because of

the fine grain size whether the symplectic silica is crystallineor amorphous is difficult to ascertain The presence of non-stoichiometric silica-rich material in the symplectite suggeststhat at least some of the silica-rich phase formed initially as aglass

Silica GlassRelatively small angular fragments of silica glass are

widespread in the breccia The silica clasts are typically nomore than 100 to 200 mm in longest dimension and occur asequant and shard-like angular clasts Some clasts are coarseenough to exhibit isotropic optics in the thin sectionindicative of amorphous silica A few clasts were analyzedand yielded stoichiometric compositions (Table 5) indicatingthat the silica may have originally been a crystalline phasethat was transformed to glass as a result of shock deformationHowever the silica was also possibly an amorphous phaseprior to shock

Pyroxene-Phyric BasaltA large clast of texturally distinct basalt was identified in

one thin section of NWA 773 The clast is characterized byprismatic phenocrysts of pyroxene up to 150 mm in width anda groundmass of finely-intergrown elongate pyroxene andfeldspar (Fig 6d) Some pyroxene phenocrysts enclose meltinclusions or channels that might have crystallized in contactwith the surrounding groundmass The pyroxene phenocrystshave BSE-bright Fe-rich chilled margins along the externalcrystal faces and along the internal margins against the meltinclusions (Fig 2)

The pyroxene phenocrysts exhibit a wide range ofcomposition with both augite and pigeonite present andsome variation in FeMg (Table 4) The augite and pigeoniteare more Fe-rich than pyroxenes from the olivine gabbrolithology (Fig 4) and the augite is enriched in Ti and Crrelative to pyroxene from both the olivine gabbro and gabbroclasts in the breccia (Fig 5) The major-element zoning ofindividual pyroxene phenocrysts in this basaltic clastcontrasts with the unzoned pyroxenes characteristic of theolivine gabbro lithology gabbroic clasts and Fe-rich lithicclasts The zoned pigeonite-augite phenocrysts with ldquohollowrdquocentral cores and the groundmass ldquosoda-strawrdquo texture ofalternating elongate pyroxene and feldspar are similar to thetextures observed in low-Ti basalts from Apollo 12 and 15(Bence et al 1971 Bence and Papike 1972)

Zoned PyroxeneOne large clast is composed of two very coarse crystals

of pyroxene (800 mm across) with zoning and distinctdomains of pigeonite and augite (Table 4) The augite exhibitsa narrow range of composition with Mg(Mg + Fe) lower thanthat of pyroxene from the olivine gabbro lithology andgabbroic clasts in the breccia (Fig 4) The augite is similar inWo-En-Fs content to augite from the pyroxene-phyric basaltic


clast (Fig 4) but contains significantly less Ti and Cr (Fig 5)Pigeonite is zoned over a range from Mg(Mg + Fe) = 062 to025 The Fe-rich pigeonite occurs in patchy BSE-brightdomains on the order of 100 mm across Some of the Fe-richpatches are cored by tiny BSE-bright inclusions of Fe Ti-oxide

AgglutinateOne coarse clast (~400 mm across) and several smaller

fragments of lunar agglutinate were identified in the brecciaThe agglutinate fragments are characterized by a frothyisotropic material with discontinuous schlieren and multipletiny mineral inclusions Broad-beam EPMA analyses of thelargest agglutinate fragment were concentrated on glassyareas within the agglutinate The results show a narrow rangeof compositions with significant SiO2 Al2O3 and CaO andminor FeO and MgO (Table 3) The anorthositic compositionof the agglutinate glass is in striking contrast to the maficcomposition of the olivine gabbro and lithic clasts in thebreccia

Yellow-Green SpheruleOne yellow-green spherule in the breccia is nearly

circular in the plane of the thin section with a diameter ofapproximately 180 mm The spherule is composed ofhomogeneous-appearing isotropic material with uniformcolor and is devoid of inclusions and internal structures suchas schlieren Broad beam EPMA analyses indicate that thespherule is also homogeneous in major elements and has analkali-depleted basaltic composition with 43 wt SiO2 and15 wt Al2O3 (Table 3) The homogeneity of the compositionand the absence of schlieren and inclusions are consistentwith a volcanic rather than an impact-related origin for thespherule (Delano 1986) however the spherule is unusuallyAl2O3-rich in comparison to melt spherules from the Apollosample collection (Delano 1986 Steele et al 1992) Using theclassification scheme of Neal and Taylor (1992) for marebasalts the spherule is low in TiO2 and K2O high in Al2O3and could be classified as ldquohigh-Al basaltrdquo similar to basaltsfrom Apollo 14 and Luna 16 However the spherule Al2O3

content is somewhat high even compared to these high-Albasalts and Na2O and K2O are depleted The pyroxene phyricmelt inclusions in olivine in NWA 773 have comparableAl2O3 contents but are much more silica-rich and have anorder of magnitude more Na2O (Table 3) Obvious differencesin most major elements distinguish the spherule from theaphyric melt inclusions in olivine and glass from anagglutinate clast in the breccia (Table 3)

A rough fit to the spherule major element composition isapproximated by a mixture of 25 agglutinate glass and 75breccia suggesting that the spherule may be an impact glassin spite of its homogeneous appearance Concentrations ofSiO2 Na2O and K2O in the spherule are all lower than thecorresponding values for the calculated mixture In fact Na2O

and K2O concentrations in the spherule are at or below ourEPMA detection limits (Table 3) and the spherule SiO2 islower than values associated with regoliths of comparableTiO2 and FeO contents (Korotev et al 2000) Theseobservations indicate that the spherule might have beenheated to temperatures high enough to homogenize and causeevaporative loss of Si Na and K during an impact event(Naney et al 1976)

WHOLE-ROCK ELEMENTAL AND OXYGEN ISOTOPIC COMPOSITION

Major element concentrations were estimated by modalrecombination for the olivine gabbro and fused bead EPMA(FB-EPMA) for the breccia (Table 8) Concentrations ofNa2O K2O CaO Cr2O3 and FeO were also determined byINAA (Table 9) and comparison of the INAA data withresults from modal recombination and FB-EPMA providessome assessment of data quality The INAA data closelyduplicate the FB-EPMA results showing internal consistencyof results for the breccia (Table 8) As might be expectedgreater discrepancies separate the modal recombinationresults from INAA data for the olivine gabbro The greatestrelative discrepancies are for K2O and Cr2O3 componentsconcentrated in phases that occur in minor abundanceAbsolute errors in modal estimates and non-representativesampling for INAA analysis may lead to substantial errors inestimating concentrations of these components The whole-rock concentrations of Na2O CaO and FeO are controlled bymodes of the major silicates The estimates of theconcentrations of these oxides are less sensitive to absoluteerrors in mode or sampling and exhibit smaller discrepancies(within about 10 relative) between the INAA and modalrecombination data (Table 8)

The major element results show low-TiO2 maficcompositions for both the olivine gabbro and breccia (Table8) High concentrations of MgO and FeO coupled with lowCaO and Al2O3 abundances suggest an affinity with mare orhighland Mg-rich rocks The olivine gabbro and the brecciahave similar concentrations of FeO but the breccia has lowerMgO consistent with the lower Mg(Mg + Fe) of maficsilicates in the breccia (Fig 3)

Taken at face value the modal recombination and FB-EPMA data suggest that K2O is more abundant in the olivinegabbro than the breccia (Table 8) but this is probably due to adiscrepancy in the two data sets most likely an overestimateof K-feldspar in the mode Abundances of K2O were alsoanalyzed by INAA (Table 8) and indicate the opposite trendnamely that the breccia is more K2O-rich than the cumulateWe favor the INAA results because these data were collectedusing the same method and because other incompatibleelements such as Ba and the rare earth elements (REE) arealso enriched in the breccia (Table 9 Fig 7)

Analyses by INAA and ICP-MS show that incompatible

542 T J Fagan et al

Table 8 Major element composition (wt) of NWA 773 olivine gabbro and breccia lithologiesa

Olivine gabbro BrecciaMethod Modal recombination INAA Fused bead EPMA INAA

SiO2 42 ndash 457 plusmn 02 ndashTiO2 04 ndash 084 plusmn 005 ndashAl2O3 53 ndash 816 plusmn 018 ndashCr2O3 08 0363 plusmn 0004 043 plusmn 003 0402 plusmn 0004FeO 205 196 plusmn 02 198 plusmn 03 199 plusmn 02MnO 024 ndash 0272 plusmn 0009 ndashMgO 255 ndash 1416 plusmn 015 ndashCaO 48 50 plusmn 03 892 plusmn 008 86 plusmn 03Na2O 015 0153 plusmn 0002 0216 plusmn 0009 0224 plusmn 0003K2O 025 0073 plusmn 0014 0111 plusmn 0008 0117 plusmn 0010P2O5 na ndash 012 plusmn 002 ndashTotal 100 ndash 987 ndash

Mg(Mg + Fe) 69 ndash 561 plusmn 02 ndashFeMn 84 ndash 72 plusmn 2 ndash

aReported uncertainties for fused bead EPMA are standard deviations of 48 analyses See the text for the discussion of uncertainties in modal recombinationdata INAA data (see Table 9) are shown for comparison The total of 100 for modal recombination data is a consequence of normalization and does not reflectthe accuracy of the compositional estimates

Table 9 INAA results from NWA 773 olivine gabbro and breccia lithologies and a gabbroic clast from the brecciaa

Olivine gabbro ldquoClastrdquob Brecciab BHVO-1c

Mass (mg) 3941 1446 2347 JSC Lit

Na2O wt 0153 plusmn 0002 0160 plusmn 0002 0224 plusmn 0003 230 226K2O wt 0073 plusmn 001 0066 plusmn 000 0117 plusmn 0010 057 052CaO wt 50 plusmn 03 54 plusmn 04 86 plusmn 03 108 114Sc mgg 231 plusmn 02 222 plusmn 02 385 plusmn 04 312 318Cr2O3 wt 0363 plusmn 0004 0238 plusmn 0003 0402 plusmn 0004 00420 0042FeO wt 196 plusmn 02 188 plusmn 02 200 plusmn 02 108 110Co mgg 860 plusmn 09 869 plusmn 09 617 plusmn 07 445 45Ni mgg 195 plusmn 17 219 plusmn 19 115 plusmn 16 127 121Sr mgg 40 plusmn 16 lt90 71 plusmn 16 398 403Zr mgg 157 plusmn 26 110 plusmn 24 183 plusmn 27 181 179Cs ngg lt150 lt90 136 plusmn 21 93 130Ba mgg 147 plusmn 8 98 plusmn 14 156 plusmn 14 130 139La mgg 863 plusmn 01 854 plusmn 010 126 plusmn 01 153 158Ce mgg 241 plusmn 04 232 plusmn 04 341 plusmn 06 375 39Nd mgg 136 plusmn 21 15 plusmn 3 23 plusmn 4 27 252Sm mgg 406 plusmn 005 405 plusmn 006 629 plusmn 008 609 62Eu mgg 0359 plusmn 0010 0355 plusmn 0008 0561 plusmn 0010 207 206Tb mgg 0832 plusmn 0025 0839 plusmn 0025 140 plusmn 003 094 096Yb mgg 292 plusmn 004 285 plusmn 006 527 plusmn 008 197 202Lu mgg 0406 plusmn 0008 0390 plusmn 0010 0752 plusmn 0016 0278 0291Hf mgg 370 plusmn 00 300 plusmn 008 470 plusmn 010 462 438Ta ngg 367 plusmn 19 372 plusmn 18 553 plusmn 18 1150 1230W ngg ndd nd 470 plusmn 160 nd 270Ir ngg lt25 lt3 lt3 nd 044Au ngg lt14 lt28 lt21 nd 16Th mgg 116 plusmn 00 126 plusmn 006 198 plusmn 008 113 108U ngg 360 plusmn 30 320 plusmn 70 520 plusmn 60 400 420

aUncertainties are 1s upper limits are 2sbSee Appendix for ICP-MS datacAn average of BHVO-1 analyzed along with the NWA 773 samples is shown along with the book values from Govindaraju (1994) which are recommended

proposed or information valuesdnd = upper limits not calculated


elements such as Zr Hf Th U and the REE occur in higherconcentrations in the breccia than the olivine gabbro (Tables 9and A1) The breccia is also relatively enriched in Scpossibly reflecting the high model abundances of pyroxenesIn contrast the olivine gabbro yielded higher concentrationsof the compatible elements Co and Ni Chromium appears tobe more abundant in the breccia but this is somewhatparadoxical because our modal estimates suggest that themode of chromite is higher in the olivine gabbro (Table 1)However the discrepancy between modal recombination andINAA Cr2O3 results (Table 8) suggests that our modalestimate of chromite in the olivine gabbro might beerroneously high Alternatively chromium abundances mayvary in different portions of the olivine gabbro In generalhowever the higher concentrations of incompatible elementsin the breccia suggest that breccia clasts are more ldquoevolvedrdquoin the igneous sense than the olivine gabbro This is consistentwith the modal data (lower olivine and greater silicaabundances of the breccia) and mineral compositions (higherK and Ba in breccia alkali feldspar and lower Mg(Mg + Fe)in mafic silicates in the breccia)

Rare earth element (REE) patterns for the breccia andolivine gabbro are parallel and reflect the higher incompatibleelement abundances of the breccia (Fig 7) Both patterns areLREE-enriched with slight downward deflections from Ce toLa and deep negative Eu anomalies Similar results have beenreported by Korotev et al (2002) Light rare earthenrichments and negative Eu anomalies are typical of thelunar KREEP component (Papike et al 1998) and LREEprofiles with slight downward deflections in Ce have recentlybeen identified in a variety of lunar mafic rocks (Tanimizuand Tanaka 2002) The concentrations of most REE in theNWA 773 olivine gabbro are similar to those of lunar

meteorite Elephant Moraine 87521 which is thought to havea mare origin (Delaney 1989 Warren and Kallemeyn 1989)but NWA 773 has a much deeper Eu anomaly (Fig 7) TheLREE-rich profile of lunar highlands meteorite CalcalongCreek is similar to that of NWA 773 but is enriched in REE bya factor of about 2 over REE concentrations in the NWA 773breccia Most of the low-TiO2 mare basalts have flat orsomewhat depleted LREE trends (Papike et al 1998) whichcontrast with the LREE-enriched pattern of NWA 773 Someof the high-Al basalts from Apollo 14 are exceptions theGroup 2 Apollo 14 basalts (Dickinson et al 1985) inparticular show an LREE-enriched pattern withconcentrations similar to those determined for the NWA 773breccia

Whole-rock oxygen isotopic analyses yield compositionsof d18O = +499permil and d17O = +250permil for the olivine gabbroand d18O = +493permil and d17O = +260permil for the breccia Thesevalues are in the range of previously identified lunar samples(Fig 8) Similar oxygen isotopic compositions for the 2lithologies are consistent with the notion that the breccia isdominated by fragments from the olivine gabbro and relatedrocks

NOBLE GASES

Table 10 gives the results of the noble gas analysesPreliminary data were given in an abstract by Eugster andLorenzetti (2001) Partitioning into the cosmogenic (c)radiogenic (r) and trapped (tr) components was carried outwith the following assumptions (4He3He)c = 52 (20Ne21Ne)c = 09 (21Ne22Ne)c = 083 (21Ne22Ne)tr = 00325(36Ar38Ar)c = 065 and (36Ar38Ar)tr = 532 The followingassumptions were obtained from the results of Y-793274

Fig 7 Rare earth element concentrations of NWA 773 (normalized to CI chondrites) compared with selected lunar samples

544 T J Fagan et al

(Eugster et al 1992) (3He21Ne)c = 073 and (38Ar21Ne)c =198 For the breccia samples 4Hetr was calculated bysubtracting radiogenic and cosmogenic 4He from themeasured 4He concentration We adopted 052 ppm U and198 ppm Th (Table 9) and a gas retention age of 28 Ga (fromY-793274) In the following we will consider the trappednoble gases to be of solar origin as numerous authors haveshown for lunar surface material (cf Eberhardt et al 1970Hohenberg et al 1970) Table 11 gives the concentrations andcomposition of the cosmogenic and solar noble gases Thedata show that the finest grain size fraction is not enriched inthe solar noble gases Such an enrichment is expected for asurface correlated component Thus the trapped 40Ar36Arratio that is diagnostic for a lunar origin of a meteorite couldnot be derived However the solar ratio 4He20Ne = 72 plusmn 07indicates that NWA 773 is of lunar origin the range for the

solar 4He20Ne ratio for lunar meteorites is 37 to 88 while allsolar gas-rich meteorites of non-lunar origin have 4He20Negt80 Furthermore the solar 20Ne22Ne ratio as well as theabundances of 21Nec and solar 20Ne in NWA 773 are similar tothose in QUE 94281 another lunar meteoritic regolithbreccia

The cosmic ray exposure (CRE) history of lunarmeteorites consists essentially of three periods 1) one ormore exposure irradiation periods on the moon each at acertain depth in the regolith 2) an irradiation during transit toEarth and 3) the time elapsed between arrival on Earth andthe meteoritersquos recovery These times can only be definedbased on the activities of several radionuclides Theconcentrations of the stable cosmogenic noble gas nucleiallow us however to calculate the total CRE time at anaverage shielding depth Here we derive the production ratesfor a 4p-exposure of the olivine gabbro fraction using themethod of Eugster and Michel (1995) inserting the targetelement abundances given in Table 8 and not taking intoaccount a shielding correction

This procedure results in a CRE age of 52 plusmn 08 Ma(Table 12) This is the ejection age of NWA 773 if the olivinegabbro fraction was not exposed to cosmic rays prior toejection on the moon If there was a pre-exposure of unknownduration for the olivine gabbro the ejection age is more recentthan 52 plusmn 08 Ma Assuming a 4p-exposure also for thebreccia fraction we obtain a travel time of 68 Ma As themeteoroid after ejection obviously consisted of both fractionsthey must have the same MoonmdashEarth travel timeConsequently the breccia fraction must have been pre-exposed on the moon Because the production rates in thelunar regolith (2p-exposure) are about half of those in freespace (4p-exposure) the duration of the lunar regolithexposure was 136 Ma When this pre-exposure occurred andwhen the olivine gabbro and breccia fractions werecompacted cannot be determined from our data The fact thatthe breccia material consists of grains loaded with solar windgases supports an exposure on the moon The olivine gabbrocontains a small addition of solar noble gases theconcentration (in units of 10-8 cm3 STPg) of solar 20Ne is 72

Fig 8 Whole-rock oxygen isotopic compositions of NWA 773breccia and olivine gabbro and other lunar rocks (Clayton andMayeda 1975 1996) Compositions are reported in d17O and d18Orelative to standard mean ocean water (SMOW) in parts perthousand Terrestrial fractionation (TF) line (Clayton 1993) is plottedfor reference

Table 10 Results of He Ne and Ar measurements of NWA 773 (concentrations in 10-8 cm3 STPg)Sample (weight) 4He 20Ne 40Ar 4He3He 20Ne22Ne 22Ne21Ne 36Ar38Ar 40Ar36Ar

Breccia340ndash750 mm(1584 mg)

181000plusmn 7000

20400plusmn 600

5470plusmn 160

2580plusmn 70

1293plusmn 013

237plusmn 04

527plusmn 005

221plusmn 003

35ndash340 mm(1501 mg)

192000plusmn 7000

22300plusmn 500

5960plusmn 160

2470plusmn 50

1289plusmn 013

234plusmn 03

527plusmn 004

225plusmn 003

lt 35 mm(1465 mg)

175000plusmn 7000

16900plusmn 500

5050plusmn 160

2240plusmn 50

1294plusmn 013

228plusmn 03

528plusmn 004

230plusmn 003

Olivine gabbro(1840 mg) 16500

plusmn 60088plusmn 03

1540plusmn 40

3400plusmn 300

35plusmn 0

142plusmn 020

183plusmn 003

1350plusmn 30


versus 19850 for the breccia This low amount may be due totraces of breccia grains in the olivine gabbro separate that weanalyzed

The 40Ar is a mixture of radiogenic trapped andcosmogenic Ar For the olivine gabbro the contributions ofArtr and Arc are calculated to be about 006 of the total 40Ar(Table 10) For the breccia fraction the amount of 40Arr

cannot be determined precisely For the olivine gabbro weobserve 1530 times 10-8 cm3 STPg 40Arr and 0073 K2O (Table9) and calculate a K-Ar age of 275 plusmn 030 Ga This age isessentially the same as that of the lunar meteorite Y-793274The geologic significance of this age is not known Ifhowever it is a crystallization age then the olivine gabbropost-dates much of the igneous evolution of the moonincluding the lunar magma ocean overturn of the cumulatesequence and the main pulse of mare volcanism (Hess andParmentier 1995 Shearer and Papike 1999)

DISCUSSION

Lunar Origin

Igneous textures of the olivine gabbro and of many clastsin the breccia indicate that NWA 773 originated from adifferentiated parent body and the oxygen isotopiccomposition independently rules out all potential knownparent bodies other than the earth the moon and enstatitechondrite-like asteroids The abundance of Fe in solidsolution with Mg in olivine and pyroxene demonstrates thatNWA 773 did not originate from an enstatite chondrite-likeparent body The presence of agglutinate fragments in thebreccia indicate that NWA 773 originated from a parent bodywithout an atmosphere ruling out a terrestrial origin and

leaving the moon as the sole candidate among known planetsand asteroids for the parent body of NWA 773

A comparison of key geochemical parameters withsamples from the Apollo and Luna missions and previouslyidentified lunar meteorites document that NWA 773originated on the moon Ratios of FeMn in NWA 773 olivineand pyroxene are characteristic of lunar rocks (Fig 3) and theLREE-enriched Eu-depleted REE pattern is typical of lunarrocks with a KREEP component (Fig 7 Bridges et al 2002Korotev et al 2002) Trapped 4He20Ne and 20Ne36Ar valuesof the NWA 773 breccia (Table 11) are similar to previouslyidentified lunar meteorites and distinct from gas-richmeteorites of non-lunar origin Other observations consistentwith a lunar origin for NWA 773 include the presence of Fe-metal ilmenite and troilite the apparent absence of ferriciron from pyroxene and spinel the F-rich composition ofapatite and the Ba-rich composition of K-feldspar

Petrogenesis Olivine Accumulation in the Olivine Gabbro

The texture of the olivine gabbro is dominated by theloose network of coarse olivine crystals (Fig 1) and the otherphases can all be described in the context of a rock thataccumulated olivine In general textures suggest thefollowing crystallization sequence olivine pigeonite augiteplagioclase and K Ba-feldspar with residual Ca-phosphatesilmenite troilite and metal Titaniferous chromite tends tooccur along olivine grain boundaries indicating that it post-dated olivine The crystallization sequence among the maficsilicates is indicated by the occurrence of olivine rimmed bypigeonite which is rimmed in turn by augite and by theabsence of conflicting crystal-rimming relationships (Fig 1)Plagioclase tends to occur in the interstices between mafic

Table 11 Cosmogenic and solar (trapped) noble gases of NWA 773 samples Concentrations in 10-8 cm3 STPga

Cosmogenic Solar

Sample 21Ne 38Ar 20Ne 4He20Ne 20Ne36Ar 20Ne22Ne

Breccia340ndash750 mm 159 ndash 20410 68 83 130835ndash340 mm 183 ndash 22230 68 85 1305lt35 mm 154 ndash 16900 79 78 1312

Average of three breccia samples 165 ndash 19850 72 82 1308

Olivine gabbro 173 047 72 ndash 86 ndashaExperimental errors (2s) 21Nec 38Arc and (4He20Ne)tr - 10 20Ne and (20Ne36Ar)tr - 4 and (20Ne22Ne)tr - 15

Table 12 Production rates and CRE ages of NWA 773P21 P38 T21 T38 Tave

Sample 10-8cm3 STPg Ma Ma

Cataclastic breccia fraction 0121a ndash 136b 136 plusmn 20 (2s)b

Olivine gabbro 0335c 0089c 52d 53d 52 plusmn 08 (2s)d

aProduction rate for 2p-exposurebExposure time on the mooncProduction rate for 4p-exposuredUpper limit for exposure time in Moon-Earth transit

546 T J Fagan et al

silicates suggesting that it crystallized after olivine andpyroxene A variety of textural relationships exist howeverand undoubtedly there was some overlap duringcrystallization of the pyroxenes plagioclase feldspar andresidual minerals

The interpretation based on textures that most of thepyroxene in the olivine gabbro crystallized prior to feldspar issupported by the low TiAl ratios in pyroxene Pyroxene withTiAl near 14 can be attributed to sub-equal proportions ofthe cation substitutions TiAliv2Mg-1Si-2 (coupled Ti-exchange) and AlviAlivMg-1Si-1 (Tschermak exchange) into aldquoquadrilateralrdquo pyroxene such as CaMgSi2O6 (Bence et al1971 Thompson 1982) while TiAl values near 12 can beattained if all of the Al present in pyroxene is coupled with Tito maintain charge balance In the olivine gabbro mostpyroxene TiAl values are near or below 14 and all are below12 In studies of lunar mafic rocks from Apollo 12 (Bence etal 1970 Bence and Papike 1972) and lunar basalt NWA 032(Fagan et al 2002) TiAl values near 14 are associated withcrystallization prior to feldspar and TiAl values near 12 areinterpreted as a consequence of co-crystallization withfeldspar We suggest a similar trend for NWA 773 Values ofTiAl near 14 for most (but not all) of the pyroxene in theolivine gabbro are consistent with crystallization of most (butnot all) of the pyroxene prior to the onset of feldsparcrystallization Pyroxene from many of the gabbroic clasts inthe breccia much of the zoned pyroxene clast andphenocrysts from the pyroxene-phyric basalt clast also haveTiAl values near 14 (Fig 5) In contrast pyroxenes from theFe-rich lithic symplectite and transitional symplectite clastshave TiAl values clustering near 12 (Fig 5) and havetextures indicating crystallization after the onset of feldsparcrystallization

The occurrence of separate grains of compositionallydistinct pigeonite and augite indicates that either a) theolivine gabbro cooled slowly enough so that the pyroxenescompletely exsolved from each other or b) pigeonite andaugite crystallized separately from a melt We favor the latterinterpretation because the very slow cooling required forcomplete separation of pigeonite and augite should also resultin thick (gt1 mm) exsolution lamellae of Ca-poororthopyroxene from pigeonite (eg Arai et al 1996however see Korotev et al [2002] who identified exsolutionlamellae in NWA 773) The polyhedral to ldquohopperrdquo texture ofolivine suggests that the olivines grew at cooling rates slowerthan about 5degChr as faster cooling rates would produce moreelongate crystals with higher surface areas (Donaldson 1976)

Augite and pigeonite coprecipitate from olivine-saturatedliquids over a wide pressure range from surface conditions topressures as high as 15 kbar for melts with MgO(MgO + FeO)= 05 (Longhi and Bertka 1996) After crystallization fromliquid the pyroxenes cooled and equilibrated at ~1150degC(assuming P = 1 bar Lindsley 1983 Sack and Ghiorso 1994)Pyroxene crystallization in the olivine gabbro did not

fractionate the liquid significantly in Mg(Mg + Fe) but didfractionate the liquid Ti(Ti + Cr) (Fig 5)

Textures and pyroxene TiAl ratios indicate that mostpyroxene crystallization was completed by the time feldsparstarted to crystallize Most plagioclase crystallized with acomposition near An90 but as crystallization continued andmelt pockets became isolated Ab- and Or-contents ofplagioclase increased Isolated residual melt pockets arerepresented by the K Ba-feldspar with splays of Ca-phosphates ilmenite troilite and metal

The residual melt pockets though minor in mode mayhave a significant effect on whole-rock trace elementchemistry because the olivine gabbro does not have anincompatible element pattern typical of cumulate rocks TheREE abundances and pattern (Fig 7) and the abundances ofHf Ta Th and U are all unusually high for a cumulate Themost incompatible elements have the highest abundanceswith La Hf Th from 36 to 39 times CI chondrite while the lessincompatible elements show smaller enrichments with Yb of18 times CI and Sc Eu of 4 to 6 times CI This demonstrates that theincompatible trace element contents are dominated by a meltcomponent This conforms with the texture which indicatesthat only olivine is a likely cumulus phase and that the modalabundance of olivine is roughly 55 of the rock

Traditionally cumulates have been interpreted to form asa consequence of crystal settling or floating in a silicateliquid and on a very large-scale cumulate differentiation byplagioclase floating and mafic silicates sinking in a lunarmagma ocean has been invoked as a major mechanism fordifferentiation of the moon (Warren 1985) However work onterrestrial layered mafic intrusions makes it clear thatcumulate textures may form from processes other than crystalsettling involving differential crystal nucleation and growthrates in situ crystallization fronts filter pressing of residualliquids and differentiation during magmatic flow (McBirneyand Noyes 1979 McBirney and Hunter 1995) Even in thecase of well-exposed cumulate intrusives on Earth the originof cumulate textures can be controversial and without a fieldcontext we do not expect to readily establish the origin ofcumulate textures in NWA 773 However crystal settling ofolivine remains a viable model

Shared Magmatic Origin of Cumulate Olivine Gabbroand Breccia Clasts

The breccia comprises several different rock types butmany appear to be from the cumulate olivine gabbro or moreFe-rich differentiates The olivine gabbro and gabbroic clastsin the breccia share similar mineral assemblages mineralcompositions and textures and both have olivines withcharacteristic andesitic melt inclusions Several pyroxene andolivine analyses from the gabbroic clasts essentially matchthose from the olivine gabbro in major element composition(Figs 3 and 4) and for the pyroxenes Ti Al and Cr


elemental ratios (Fig 5) Oxygen isotopic compositions of thebreccia and cumulate plot close together within the range ofvalues determined for lunar samples (Fig 8) suggesting thatthe breccia and cumulate are derived from a similar localsource on the moon Related origins for the cumulate olivinegabbro and most clasts in the breccia are also implied by theparallel REE patterns (also see Korotev et al 2002) Thesimilar patterns suggest that REE concentrations of bothlithologies are dominated by the same REE-rich minerals(most likely whitlockite) that crystallized from relatedliquids The higher bulk REE concentrations of the brecciacan be explained as a result of the presence of clasts thatcrystallized from differentiated liquids

Pyroxene compositions from the gabbroic clasts extendto lower Mg(Mg + Fe) and higher Ti(Ti + Cr) values onsimple trends from compositions characteristic of the olivinegabbro (Figs 4 and 5) as would be expected for afractionating igneous system (Arai et al 1996 2002) Incontrast to the broad continuous range in Mg(Mg + Fe) forpyroxene olivine from the gabbroic clasts exhibits only alimited trend toward lower Mg(Mg + Fe) A compositionalgap separates olivine in the gabbroic clasts from the olivineobserved in Fe-rich lithic and symplectic clasts (Fig 3) Thiscompositional gap can be explained as a consequence of 1)early crystallization of olivine which then ceased tocrystallize while pigeonite and augite grew in the meltfollowed by 2) Fe-enrichment into the ldquoforbidden zonerdquo of thepyroxene quadrilateral where pigeonite gives way to fayalite+ silica + hedenbergitic pyroxene (Lindsley and Munoz1969) In contrast to the cumulate olivine gabbro stage ofcrystallization clasts in the breccia appear to have formedfrom a magmatic system in which mafic silicates fractionatedthe remaining melt to extremely low Mg(Mg + Fe) and highTi(Ti + Cr) (Figs 3 4 and 5) As the system became Fe-richpigeonite gave way to Ca-rich clinopyroxene fayaliticolivine and a SiO2-rich phase

Late-stage differentiates are represented by fayaliticrocks including the symplectites fayalite gabbros andfayalite granites The pyroxenes in these clasts have low Mg(Mg + Fe) and high Ti(Ti + Cr) indicative of crystallizationfrom evolved liquids and TiAl ratios in excess of 05suggestive of crystallization after the onset of feldsparcrystallization Plagioclase feldspar in the symplectic clasts isrelatively An-poor (An ~70) and the K Ba-feldspar with thehighest BaO contents analyzed are from Fe-rich lithic clastsalso indicating that the symplectites and Fe-rich lithic clastsformed from incompatible-element-rich liquids Thisinference is supported by the identification of baddeleyite inone of the fayalite gabbro fragments Fayalite-bearinggranitic clasts are not abundant but their presence suggeststhat some residual liquids reached alkali- and silica-richcompositions after extreme iron-enrichment fromcrystallization of the olivine-gabbrogabbrofayalitic-rocksequence Silica clasts though minor in mode (Table 1) are

widespread in the breccia and may be fragments of SiO2-richrocks from late stages of the olivine-gabbrogabbrofayalitic-rock sequence

Iron-rich symplectites have been observed in other lunarsamples (Koeberl et al 1993 Yanai and Kojima 1991) and insome cases may form during the breakdown of pyroxferroiteto fayalite + silica In NWA 773 the presence of K2O- andAl2O3-bearing non-stoichiometric silica-rich glass as a phasein the symplectite is not consistent with an origin by thebreakdown of a pre-existing stoichiometric solid Rather thesymplectite in NWA 773 appears to have formed from directcrystallization or quenching from one or more liquidsImmiscible liquids in FeO-rich silicate systems have beenidentified in experiments and in lunar samples (Roedder andWeiblen 1971 Rutherford et al 1974 Roedder 1978 Ryersonand Hess 1978 Taylor et al 1980 Shearer et al 1997 Jolliffet al 1999) and probably exsolved during late-stagedifferentiation of Fe-rich gabbroic rocks in NWA 773Immiscible liquids rapid crystal growth rates and relativelyslow diffusion rates of cations in liquids are some of thefactors that may have led to the symplectic texture in NWA773

The presence of 2 possibly immiscible silicate liquidsduring earlier stages of igneous differentiation is suggested bythe andesitic and silica-rich melt inclusions in olivine fromthe cumulate olivine gabbro Some broad beam analyses ofthe silica-rich inclusions overlapped with Ca-phosphatecrystals (internal to the inclusion) resulting in high P2O5 inindividual analyses but in general P2O5 concentrations areconsistently higher in the andesitic inclusions (Table 3)These results with the more SiO2-poor composition enrichedin P2O5 are consistent with the 2 sets of melt inclusionsrelated by immiscibility rather than crystal fractionation(Ryerson and Hess 1978) Both sets of melt inclusions areunusually SiO2-rich to be trapped in such an olivine-rich rockand their compositions may reflect post-trapping alterationand reaction with olivine host crystals (Danyushevsky et al2002 Norman et al 2002)

FeO-Enrichment Trend and Contrast with SiO2-Enrichment in 15405

The cumulate olivine gabbro lithology and gabbroic Fe-rich lithic and symplectic clasts from the breccia can beinterpreted as a suite from a mafic igneous system that wascharacterized by Fe-enrichment to extremely low values ofMg(Mg + Fe) Some granitic rocks formed after the Mg(Mg+ Fe) of residual liquids reached values near zero This Fe-enrichment trend contrasts with KREEP-rich fragmentsidentified in lunar breccia 15405 (Ryder 1976) Clasts ofKREEP basalt quartz monzodiorite and granite in 15405were interpreted by Ryder as fragments of a compositemagmatic system in which monzodiorite and subsequentlygranite were produced by crystal fractionation from anoriginal magma with a composition similar to the KREEP

548 T J Fagan et al

basalt Pyroxenes in 15405 reached Mg(Mg + Fe) as low asabout 030 significantly fractionated with respect topyroxenes from the basalt clasts in the breccia but far from theextreme Fe-rich compositions found in NWA 773

Of course sample 15405 and NWA 773 are breccias andcannot be taken as complete sample suites from igneousbodies But if the rock fragments are representative of themagmatic units from which they come then they show amarked contrast in differentiation Sample 15405 reflects atrend of increasing silica-content with moderate Fe-enrichment while NWA 773 reflects an extreme Fe-enrichment trend These trends are comparable in a broadsense to the terrestrial silica-enrichment (or ldquoBowenrdquo) trendassociated with calc-alkaline magmas and the Fe-enrichment(or ldquoFennerrdquo) trend associated with tholeiitic mafic bodiessuch as the Skaergaard intrusion (Brown and Vincent 1963also see McBirney 1993) In terrestrial systems the differencebetween these trends has been associated with variations inf(O2) high oxygen fugacities can lead to silica enrichment asFe is partly oxidized to the ferric form and is precipitated inoxide minerals in addition to mafic silicates (eg Yagi andTakeshita 1987) under low oxygen fugacities most Fe isferrous and precipitates in mafic silicates that become moreFe-rich with fractionation In a lunar setting this explanationdoes not hold because of the absence of ferric iron The extentof Fe-enrichment may still have been controlled by oxygenfugacity but in the opposite sense to that on Earth namely arelatively high lunar oxygen fugacity may have limited theprecipitation of Fe in metal or sulfides resulting in moreextreme Fe-enrichment in the silicates (Snyder et al 1999a)

Alternatively the contrast between silica-enrichment in15405 and iron-enrichment in NWA 773 may have stemmedfrom differences in dynamics that led to more effectiveisolation of residual liquid in the NWA 773 magmatic systemCumulate processing in the NWA 773 system may havedepleted residual liquids in Mg(Mg + Fe) leading to a broadrange of lower Mg(Mg + Fe) values in late differentiates Awide range of compositions could have crystallized in a smallspatial domain if the magmatic body was relatively smallsuch as a sill or ponded lava flow (Helz 1987 Shirley 1987)or if multiple packets of magma underwent differentiationindependently as is found in terrestrial layered maficintrusions (Kruger and Marsh 1985 Boudreau and McBirney1997 McBirney and Nicolas 1997) and ophiolitic gabbros(Springer 1980 Pallister and Hopson 1981)

Exotic Clasts in the Breccia

Some clasts in the breccia appear to be unrelated tomagmatic evolution of the olivine-gabbrogabbrofayalitic-rock trend Pyroxene phenocrysts from the phyric basalt clast(Fig 6) are enriched in Ti Al and Cr compared to clasts fromthe olivine-gabbrogabbrofayalitic-rock suite (Table 4)These pyroxene phenocrysts have distinct Ti(Ti + Cr) and

Mg(Mg + Fe) values (Fig 5) indicating that the highconcentrations of Ti Al and Cr are not due to differentiationfrom the olivine-gabbrogabbrofayalitic-rock trend (Fig 5)This clast probably originates from a mare basalt

The composition of the agglutinate glass is anorthositic(Table 3) distinctly enriched in CaO and Al2O3 and depletedin FeO + MgO compared to the olivine gabbro and lithicbreccia fragments Agglutinate glass is thought to form fromfusion of the finest fraction of regolith during meteorite andmicrometeorite bombardment (Simon et al 1985) and thusmay not be precisely representative of the ldquowhole-rockrdquocomposition of the regolith from which it forms In this casehowever the contrast between compositions of theagglutinate glass and lithic fragments is so strong thatderivation of the agglutinate from a regolith composed solelyof the olivine gabbro lithology and gabbroic and fayaliticclasts from the breccia is untenable The agglutinatecomposition indicates an origin from highland anorthosites orrelated rocks

The yellow-green spherule also probably represents alithologic unit that did not form from magmatic evolution ofthe olivine-gabbrogabbrofayalitic-rock series The spheruleis enriched in Al2O3 at a SiO2-content comparable to that ofthe olivine gabbro (Tables 3 and 8) thus removing cumulateolivine from the olivine gabbro composition cannot producethe composition of the spherule The spherule is enriched inAl2O3 and depleted in SiO2 relative to both sets of meltinclusions in olivine and appears unrelated by any simplefractionation relationship to either set of inclusions

As discussed previously (Mineralogy and TexturesmdashBreccia Lithology) the spherule may be an impact glass froma mixture of the breccia and anorthositic highland materialThe aluminous compositions of the spherule and agglutinateare significant because they indicate a highland component inthe NWA 773 breccia

Comparison with Other Lunar Rocks

The geochemical data compiled during this study clearlyindicate a lunar origin of NWA 773 but how this meteoritefits with previously identified lunar rocks is less clear-cutThe deep negative Eu anomaly indicates that NWA 773 wasderived from a Eu-depleted source commonly inferred to bea consequence of plagioclase fractionation For lunar rocksthe Eu-depletion is associated with a residual liquid (KREEPor urKREEP for a hypothetical liquid closely associated withthe lunar magma ocean) fractionated by the sinking of maficsilicates and the flotation of an anorthosite-rich crust during aprimordial lunar magma ocean (Warren 1985 Warren andKallemeyn 1993b Shearer and Papike 1999) The Eu-depletion in NWA 773 coupled with its mafic major elementcomposition indicate that NWA 773 was extracted frommafic or ultramafic material that post-dated plagioclasefractionation in the lunar magma ocean


The most obvious set of mafic lunar rocks that post-datedthe magma ocean are the mare basalts but as discussedpreviously most mare basalts from the Apollo and Lunamissions have flat or depleted LREE patterns distinct from theLREE-enriched pattern of NWA 773 Some of the Apollo 14high-Al basalts are also LREE enriched (Dickinson et al1985) but these rocks are distinctly more aluminous than theNWA 773 olivine gabbro and breccia and do not make a goodmatch for NWA 773 However the similar REE patternssuggest that NWA 773 and the high-Al basalts originatedfrom liquids that melted with or assimilated a lithology withelevated incompatible elements similar to KREEP Whole-rock and mineral REE analyses reported by others alsosuggest that at least some of the parent material of NWA 773had a KREEP-like trace element pattern (Bridges et al 2002Korotev et al 2002) A pyroxene-phyric basaltic clast in theNWA 773 breccia has distinctive textures similar to pigeonitebasalts from Apollo 12 and 15 and this clast probablyoriginated from the lunar maria However as discussed above(Exotic Clasts in the Breccia) pyroxene from this clastdeviates from compositional trends identified in otherpyroxenes from the olivine gabbro and breccia and the clastappears to be unrelated to the olivine gabbro and majority oflithic fragments in the breccia

Several lunar meteorites share a mafic composition andLREE-enriched pattern generally similar to NWA 773 Lunarmeteorites with whole-rock Al2O3 lt20 wt and LaYb gt19include Y-793274 and QUE 94281 (Jolliff et al 1998) EET87521 and EET 96008 (Delaney 1989 Warren andKallemeyn 1989 Snyder et al 1999a) Northwest Africa 032(Fagan et al 2002) and Dhofar 287 (Taylor et al 2001) Infact it has been pointed out (Snyder 1999b) that all theanalyzed lunar mafic meteorites are LREE-enriched exceptfor the coarse-grained non-brecciated Y-793169 and A-881757 (Koeberl et al 1993 Warren and Kallemeyn 1993a)The LREE-enrichment of lunar mafic meteorites is not duesolely to physical mixing of highland components in brecciasbecause NWA 032 is an unbrecciated basalt The analysis ofDho 287 by Taylor et al (2001) is of a basalt fragment thatcomprises much of the meteorite and the unbrecciated olivinegabbro lithology of NWA 773 also yields a LREE-enrichedpattern In addition to the similarity in REE several of thesemeteorites including EET 87521 QUE 94281 EET 96008and Y-981031 also have clasts with highly evolvedhedenbergite + fayalite + silica-rich phase assemblagessimilar to those that occur in the NWA 773 breccia (Delaney1989 Arai and Warren 1999 Arai et al 2002 Jolliff et al1998 Snyder et al 1999a)

In spite of these similarities it is unlikely that anypreviously identified lunar meteorite is a pair of NWA 773The negative Eu anomaly of NWA 773 (SmEu = 112 for theolivine gabbro 113 for the breccia) is much deeper than thatof the other lunar mafic meteorites among the meteoritesmentioned above NWA 032 has the second deepest Eu

anomaly with SmEu = 60 (Fagan et al 2002) nearly half ofthe value for NWA 773 Furthermore O-isotopiccompositions of the NWA 773 gabbro and breccia differ fromthose of other lunar meteorites (Fig 8)

The Mg-suite or Mg-rich nonmare rocks (Papike et al1998 Warren and Wasson 1977) share some similarities inmineralogy with NWA 773 but are distinct in keygeochemical parameters Rocks in this group are very diversebut are generally characterized by feldspar with lower An-contents mafic silicates with higher Mg(Mg + Fe) andhigher mafic silicateplagioclase feldspar ratios than rocks ofthe ferroan anorthosite suite (Warren and Wasson 1977)James and Flohr (1983) divided Mg-rich nonmare rocks intonorites dominated by orthopyroxene and plagioclase feldsparand gabbronorites with significant clinopyroxene NWA 773clearly bears a closer resemblance to the gabbronoritesubgroup in mineralogy although baddeleyite which isassociated with the norite subgroup (James and Flohr 1983)is present in NWA 773 Inversion of ion microprobe analysesof plagioclase feldspar and pyroxenes from magnesian suitenorites troctolites and anorthosites indicate that many ofthese rocks crystallized from liquids with KREEP-like traceelement signatures (Papike et al 1996 Shervais and McGee1998) In general this conforms with similar calculations forNWA 773 by Bridges et al (2002) and with the whole-rocktrace element data reported here (Table 9) and elsewhere(Korotev et al 2002)

In spite of the similarities NWA 773 differs from somegeochemical trends characteristic of the Mg-suite Althoughsome of the gabbronorites tabulated by James and Flohr(1983) are characterized by moderate LREE-enrichmentnone of them has a Eu-anomaly as deep as that of NWA 773Furthermore Warren (1986 also see Shearer and Papike1999) divided the Mg-suite from ferroan anorthosites basedon molar Na(Na + Ca) and Mg(Mg + Fe) Using theseparameters the NWA 773 breccia plots in the ferroananorthosite field while the olivine gabbro falls along theboundary of values for the Mg-suite and ferroan anorthosites(Fig 9) The breccia whole-rock composition results from avariety of clasts and cannot be considered ldquoigneousrdquo thus thesimilarity of breccia and ferroan anorthosite values maysimply be coincidental Nonetheless if as we propose theNWA 773 breccia is dominated by rocks from an olivine-gabbrogabbrofayalitic-rock differentiation suite we wouldexpect the breccia whole-rock composition to reflect anintermediate composition between suite endmembers IfNWA 773 truly belongs with the Mg-suite we would expectthe Na(Na + Ca) and Mg(Mg + Fe) values of the breccia andMg-suite to be similar The low Na(Na + Ca) of the breccia(Fig 9) may reflect the Fe-enrichment ldquotholeiiticrdquo trend wepropose for NWA 773 (see FeO-Enrichment Trend andContrast with SiO2-Enrichment in 15405)

Despite these differences NWA 773 shares someimportant similarities with the Mg-suite and NWA 773

550 T J Fagan et al

probably shared some elements of petrogenesis with this setof rocks during the magmatic evolution of the moon Basedon mass balance modelling Warren and Kallemeyn (1993b)propose that up to 30 of the lunar crust is composed ofmagnesian igneous rocks that intruded into an older ferroananorthosite crust The NWA 773 olivine-gabbrogabbrofayalitic-rock trend reflects Fe-enrichment duringfractionation of a Mg-rich original liquid This igneoussystem may have been sited in either a thick lava flow orshallow-level intrusive in the lunar highland crust (James1980) Possible terrestrial analogues include layered maficintrusives (Kruger and Marsh 1985 Boudreau and McBirney1997 McBirney and Nicolas 1997) ophiolitic gabbros(Springer 1980 Pallister and Hopson 1981) sills (Shirley1987) and ponded lavas (Helz 1987)

CONCLUSIONS

The meteorite Northwest Africa 773 is from the moonThe meteorite consists of two lithologies a two-pyroxenecumulate olivine gabbro and a regolith breccia The brecciahas fragmental textures and includes a variety of materialsbut is dominated by gabbroic and fayalite-bearing clasts Thebreccia contains large concentrations of solar gases while theolivine gabbro is solar gas-poor The 4He20Ne ratio in thebreccia fraction is 72 plusmn 07 confirming a lunar origin forNWA 773 The breccia material resided for over 100 Ma inthe lunar regolith The olivine gabbro yields a lunar ejectiontime of lt52 Ma and a K-Ar age of 275 plusmn 030 Ga This ageis close to that of lunar meteorite Y-793274

The NWA 773 olivine gabbro lithology and gabbroic andfayalitic lithic fragments in the breccia are from a magmatic

system that evolved by accumulation of olivine trapping ofKREEP-like liquids in intercumulus domains exsolution ofcoexisting immiscible silicate liquids and extreme Fe-enrichment of late-stage liquids Pyroxene compositionaltrends from the olivine gabbro lithology show that earlyaccumulation of mafic phases increased Ti(Ti + Cr) ofavailable liquid while Mg(Mg + Fe) remained constantEventually the liquid Mg(Mg + Fe) diminished resulting inthe crystallization of gabbroic rocks with pyroxenes showinga continuous trend of increasing Ti(Ti + Cr) and decreasingMg(Mg + Fe) The early crystallization of Mg-rich olivinewas followed by a hiatus in olivine crystallization olivinecrystallization resumed as the system evolved to very Fe-richcompositions Two compositionally distinct silicate liquidswere present early during crystallization and were trapped asmelt inclusions in cumulate olivine These liquids may havebeen immiscible Immiscible liquids may also have beenpresent during late-stage crystallization as the system evolvedto very low Mg(Mg + Fe)

From the variety of lithic fragments that appear to berelated by magmatic differentiation we infer that most of thecomponents of NWA 773 are from a complex magmatic bodyin which the liquid or packets of liquid underwent extremeranges of Fe-enrichment during crystallization A likelycandidate for this type of magmatic body is a shallow-levellayered mafic intrusion broadly similar to tholeiitic terrestrialintrusions (James 1980) or a ponded lava flow that underwentcumulate differentiation The presence of agglutinate and amelt spherule with aluminous compositions provides a link toanorthositic rocks and suggests that the olivine-gabbrogabbrofayalitic-rock magmatic body was intruded into orextruded on the lunar highland crust

The LREE-rich trace element signature of NWA 773 issimilar to several other mafic lunar meteorites but distinctfrom the mare basalts sampled during Apollo and Lunamissions The evolution of LREE-rich mafic rocks in thecontext of the magmatic evolution of the moon remains to beestablished

AcknowledgmentsndashThis work was supported by NASAGrants NAG 5ndash4212 (K Keil P I) and RTOP 344ndash31ndash10ndash18(D W Mittlefehldt P I) NSF Grant EAR-9815338 (R NClayton P I) and the Swiss National Science FoundationMuch of the manuscript preparation took place at the TokyoInstitute of Technology where the senior author wassupported by a post-doctoral fellowship from the JapanSociety for the Promotion of Science Our assessment of theREE data and comparisons of NWA 773 with lunar andterrestrial rocks benefited from discussions with MasaharuTanimizu B Ray Hawke and Paul Buchanan This projectowes an obvious debt to Graham Ryder who proposed amagmatic differentiation trend for igneous clasts in Apollosample 15405 The manuscript was improved by reviewsfrom D S Burnett and R L Korotev This is Hawairsquoi

Fig 9 Discrimination of ferroan anorthosites from Mg-rich rocksbased on whole-rock molar Na(Na + Ca) and Mg(Mg+Fe) afterWarren (1986) (dashed line at lower right encompasses 19 troctolites)The values for NWA 773 breccia and olivine gabbro are also plotted


Institute of Geophysics and Planetology Publication Number1238 and School of Ocean and Earth Science and TechnologyPublication Number 6039

Editorial HandlingmdashDr Urs Kraumlhenbuumlhl

REFERENCES

Arai T Takeda H and Warren P H 1996 Four lunar maremeteorites Crystallization trends of pyroxenes and spinelsMeteoritics amp Planetary Science 31877ndash892

Arai T and Warren P H 1999 Lunar meteorite Queen AlexandraRange 94281 Glass compositions and other evidence of launchpairing with Yamato-793274 Meteoritics amp Planetary Science34209ndash234

Arai T Ishi T and Otsuki M 2002 Mineralogical study of a newlunar meteorite Yamato-981031 (abstract 2064) 33rd Lunar andPlanetary Science Conference CD-ROM

Bence A E and Papike J J 1972 Pyroxenes as recorders of lunarbasalt petrogenesis Chemical trends due to crystal-liquidinteraction Proceedings 3rd Lunar and Planetary ScienceConference pp 431ndash469

Bence A E Papike J J and Prewitt C T 1970 Apollo 12clinopyroxenes Chemical trends Earth and Planetary ScienceLetters 8393ndash399

Bence A E Papike J J and Lindsley D H 1971 Crystallizationhistories of clinopyroxenes in two porphyritic rocks fromOceanus Procellarum Proceedings 2nd Lunar and PlanetaryScience Conference pp 559ndash574

Boudreau A E and McBirney A R 1997 The Skaergaard series PartIII Non-dynamic layering Journal of Petrology 381003ndash1020

Bridges J C Jeffries T E and Grady M M 2002 Trace elementsignatures of trapped KREEP in olivine-rich clasts withinlunar meteorite NWA 773 Meteoritics amp Planetary Science37A24

Brown G M and Vincent E A 1963 Pyroxenes from the late stagesof fractionation of the Skaergaard intrusion East GreenlandJournal of Petrology 4175ndash197

Brown R W 1977 A sample fusion technique for whole rockanalysis with the electron microprobe Geochimica etCosmochimica Acta 41435ndash438

Clayton R N 1993 Oxygen isotopes in meteorites Annual Reviewof Earth and Planetary Science 21115ndash149

Clayton R N and Mayeda T K 1963 The use of brominepentafluoride in the extraction of oxygen from oxides andsilicates for isotopic analysis Geochimica et Cosmochimica Acta2743ndash52

Clayton R N and Mayeda T K 1975 Genetic relations between themoon and meteorites Proceedings 6th Lunar and PlanetaryScience Conference pp 1761ndash1769

Clayton R N and Mayeda T K 1983 Oxygen isotopes in eucritesshergottites nakhlites and chassignites Earth and PlanetaryScience Letters 621ndash6

Clayton R N and Mayeda T K 1996 Oxygen isotope studies ofachondrites Geochimica et Cosmochimica Acta 601999ndash2017

Danyushevsky L V McNeill A W and Sobolev A V 2002Experimental and petrologic studies of melt inclusions inphenocryts from mantle-derived magmas An overview oftechniques advantages and complications Chemical Geology1835ndash24

Delaney J S 1989 Lunar basalt breccia identified among Antarcticmeteorites Nature 342889ndash890

Delano J W 1986 Pristine lunar glasses Criteria data andimplications Proceedings 16th Lunar and Planetary Science

Conference pp D201ndashD213Dickinson T Taylor G J Keil K Schmitt R A Hughes S S and

Smith M R 1985 Apollo 14 aluminous mare basalts and theirpossible relationship to KREEP Proceedings 15th Lunar andPlanetary Science Conference pp C365ndashC374

Donaldson C H 1976 An experimental investigation of olivinemorphology Contributions to Mineralogy and Petrology 57187ndash213

Eberhardt P Geiss J Graf H Groumlgler N Kraumlhenbuumlhl U SchwallerH Schwarzmuumlller J and Stettler A 1970 Trapped solar windnoble gases exposure age and KAr-age in Apollo 11 lunar finematerial Proceedings 1st Lunar and Planetary ScienceConference pp 1037ndash1070

Eugster O and Lorenzetti S 2001 Exposure history of somedifferentiated and lunar meteorites Meteoritics amp PlanetaryScience 36A54ndashA55

Eugster O and Michel T 1995 Common asteroid break-up events ofeucrites diogenites and howardites and cosmic-ray exposureproduction rates for noble gases in achondrites Geochimica etCosmochimica Acta 59177ndash199

Eugster O Michel T and Niedermann S 1992 Solar wind andcosmic-ray exposure history of lunar meteorite Yamato-793274Proceedings of the NIPR Symposium on Antarctic Meteorites 521ndash33

Eugster O Michel T Niedermann S Wang D and Yi W 1993 Therecord of cosmogenic radiogenic fissiogenic and trapped noblegases in recently recovered Chinese and other chondritesGeochimica et Cosmochimica Acta 571115ndash1142

Fagan T J Taylor G J Keil K Bunch T E Wittke J H KorotevR L Jolliff B L Gillis J J Haskin L A Jarosewich E JClayton R N Mayeda T K Fernandes V A Burgess RTurner G Eugster O and Lorenzetti S 2002 Northwest Africa032 Product of lunar volcanism Meteoritics amp PlanetaryScience 37371ndash394

Govindaraju K 1994 1994 compilation of working values andsample descriptions for 383 geostandards GeostandardsNewsletter 18 158 p

Head J W III and Wilson L 1992 Lunar mare volcanismStratigraphy eruption conditions and the evolution of secondarycrusts Geochimica et Cosmochimica Acta 562155ndash2175

Helz R T 1987 Differentiation behavior of Kilauea Iki lava lakeKilauea volcano Hawaii An overview of past and current workIn Magmatic processes Physicochemical principles edited byMysen B O University Park The Geochemical Society pp241ndash258

Hess P C and Parmentier E M 1995 A model of the thermal andchemical evolution of the moonrsquos interior Implications for theonset of mare volcanism Earth and Planetary Science Letters134501ndash514

Hicks T L Fagan T J and Keil K 2000 Metamorphic sequence ofunequilibrated EH chondrites using modal olivine and silicaabundance (abstract 1491) 31st Lunar and Planetary ScienceConference CD-ROM

Hicks T L Taylor G J Fagan T J Krot A N and Keil K 2002Automated mapping of meteorite thin sections using imageprocessing software (abstract 1055) 33rd Lunar and PlanetaryScience Conference CD-ROM

Hohenberg C M Davis P K Kaiser W A Lewis R S andReynolds J H 1970 Trapped and cosmogenic rare gases fromstepwise heating of Apollo 11 samples Proceedings 1st Lunarand Planetary Science Conference pp 1283ndash1309

James O B 1980 Rocks of the early lunar crust Proceedings 11thLunar and Planetary Science Conference pp 365ndash393

James O B and Flohr M K 1983 Subdivision of the Mg-suitenoritic rocks into Mg-gabbronorites and Mg-norites

552 T J Fagan et al

Proceedings 13th Lunar and Planetary Science Conference ppA603ndashA614

Jolliff B L Korotev R L and Rockow K M 1998 Geochemistryand petrology of lunar meteorite Queen Alexandra Range 94281a mixed mare and highland regolith breccia with specialemphasis on very-low-titanium mafic components Meteoriticsamp Planetary Science 33581ndash601

Jolliff B L Floss C McCallum I S and Schwartz J M 1999Geochemistry petrology and cooling history of 141617373 Aplutonic lunar sample with textural evidence of granitic-fractionseparation by silicate-liquid immiscibility AmericanMineralogist 84821ndash837

Jolliff B L Gillis J J Haskin L A Korotev R L and WieczorekM A 2000 Major lunar crustal terranes Surface expressionsand crust-mantle origins Journal of Geophysical Research 1054197ndash4216

Koeberl C Kurat G and Brandstaumltter F 1993 Gabbroic lunar maremeteorites Asuka-881757 (Asuka-31) and Yamato-793169Geochemical and mineralogical study Proceedings of the NIPRSymposium on Antarctic Meteorites 614ndash34

Korotev R L Jolliff B L and Haskin L A 2000 The concentrationof oxygen (and silicon) in lunar materials (abstract 1210) 31stLunar and Planetary Science Conference CD-ROM

Korotev R L Zeigler R A Jolliff B L and Haskin L A 2002Northwest Africa 773mdashAn unusual rock from the lunar mariaMeteoritics amp Planetary Science 37A81

Kruger F J and Marsh J S 1985 The mineralogy petrology andorigin of the Merensky cyclic unit in the western BushveldComplex Economic Geology 80958ndash974

Lawrence D H Feldman W C Barraclough B L Binder A BElphic R C Maurice S Miller M C and Prettyman T H 2000Thorium abundances on the lunar surface Journal ofGeophysical Research 10520307ndash20331

Lindsley D H 1983 Pyroxene thermometry American Mineralogist68477ndash493

Lindsley D H and Munoz J L 1969 Subsolidus relations along thejoin hedenbergite-ferrosilite American Journal of Science 267-A295ndash327

Longhi J and Bertka C M 1996 Graphical analysis of pigeonite-augite liquidus equilibria American Mineralogist 81685ndash695

McBirney A R 1993 Igneous petrology Boston Jones and Bartlett508 p

McBirney A R and Hunter R H 1995 The cumulate paradigmreconsidered Journal of Geology 103114ndash122

McBirney A R and Nicolas A 1997 The Skaergaard layered seriesPart II Magmatic flow and dynamic layering Journal ofPetrology 38569ndash580

McBirney A R and Noyes R M 1979 Crystallization and layeringof the Skaergaard intrusion Journal of Petrology 20487ndash554

Mittlefehldt D W 1994 The genesis of diogenites and HED parentbody petrogenesis Geochimica et Cosmochimica Acta 581537ndash1552

Naney M T Crowl D M and Papike J J 1976 The Apollo 16 drillcore Statistical analysis of glass chemistry and thecharacterization of a high alumina-silica poor (HASP) glassProceedings 7th Lunar and Planetary Science Conference pp155ndash184

Neal C R and Taylor L A 1992 Petrogenesis of mare basalts Arecord of lunar volcanism Geochimica et Cosmochimica Acta562177ndash2211

Neal C R Hacker M D Snyder G A Taylor L A Liu Y G andSchmitt R A 1994 Basalt generation at the Apollo 12 site Part2 Source heterogeneity multiple melts and crustalcontamination Meteoritics 29349ndash361

Norman M D and Mittlefehldt D W 2002 Impact processing of

chondritic planetesimals Siderophile and volatile elementfractionation in the Chico L chondrite Meteoritics amp PlanetaryScience 37329ndash344

Norman M D Griffin W L Pearson N J Garcia M O andOrsquoReilly S Y 1998 Quantitative analysis of trace elementabundances in glasses and minerals A comparison of laserablation ICPMS solution ICPMS proton microprobe andelectron microprobe data Journal of Analytical AtomicSpectroscopy 13477ndash482

Norman M D Garcia M O Kamenetsky V S and Nielsen R L2002 Olivine-hosted melt inclusions in Hawaiian picritesEquilibration melting and plume source characteristicsChemical Geology 183143ndash168

Pallister J S and Hopson C A 1981 Samail ophiolite plutonic suiteField relations phase variation cryptic variation and layeringand a model of a spreading ridge magma chamber Jounal ofGeophysical Research 862593ndash2644

Papike J J 1998 Comparative planetary mineralogy Chemistry ofmelt-derived pyroxene feldspar and olivine In Planetarymaterials edited by Papike J J Washington DC MineralogicalSociety of America pp 7-1ndash7-11

Papike J J Fowler W G Shearer C K and Layne G D 1996 Ionmicroprobe investigation of plagioclase and orthopyroxene fromlunar Mg-suite norites Implications for calculating parental meltREE concentrations and for assessing postcrystallization REEredistribution Geochimica et Cosmochimica Acta 603967ndash3978

Papike J J Ryder G and Shearer C K 1998 Lunar samples InPlanetary materials edited by Papike J J Washington DCMineralogical Society of America pp 5-1ndash5-234

Polnau E and Eugster O 1998 Cosmic-ray produced radiogenicand solar noble gases in lunar meteorites Queen AlexandraRange 94269 and 94281 Meteoritics amp Planetary Science 33313ndash319

Roedder E 1978 Silicate liquid immiscibility in magmas and in thesystem K2O-FeO-Al2O3-SiO2 An example of serendipityGeochimica et Cosmochimica Acta 421597ndash1617

Roedder E and Weiblen P W 1971 Petrology of silicate meltinclusions Apollo 11 and 12 and terrestrial equivalentsProdeedings 2nd Lunar and Planetary Science Conference pp507ndash528

Rutherford M J Hess P C and Daniel G H 1974 Experimentalliquid line of descent and liquid immiscibility for basalt 70017Proceedings 5th Lunar and Planetary Science Conference pp569ndash583

Ryder G 1976 Lunar sample 15405 Remnant of a KREEP basalt-granite differentiated pluton Earth and Planetary ScienceLetters 29255ndash268

Ryder G and Schuraytz B C 2001 Chemical variation of the largeApollo 15 olivine-normative mare basalt rock samples Journalof Geophysical Research 1061435ndash1451

Ryerson F J and Hess P C 1978 Implications of liquid-liquiddistribution coefficients to mineral-liquid partitioningGeochimica et Cosmochimica Acta 42921ndash932

Sack R O and Ghiorso M S 1994 Thermodynamics ofmulticomponent pyroxenes II Phase relations in thequadrilateral Contributions to Mineralogy and Petrology 116287ndash300

Schmitt H H 1991 Evolution of the moon Apollo model AmericanMineralogist 76773ndash784

Shearer C K and Papike J J 1999 Magmatic evolution of the moonAmerican Mineralogist 841469ndash1494

Shearer C K Wiedenbeck M Spilde M N and Papike J J 1997Minor and trace element partitioning between immiscible high-Fe basalts and high-Si rhyolites An example from melt


inclusions in mare basalts (abstract 1236) 27th Lunar andPlanetary Science Conference CD-ROM

Shervais J W and McGee J J 1998 Ion and electron microprobestudy of troctolites norite and anorthosites from Apollo 14Evidence for urKREEP assimilation during petrogenesis ofApollo 14 Mg-suite rocks Geochimica et Cosmochimica Acta623009ndash3023

Shirley D N 1987 Differentiation and compaction in the Palisadessill New Jersey Journal of Petrology 28835ndash865

Simon S B Papike J J Houmlrz F and See T H 1985 Anexperimental investigation of agglutinate melting mechanismsShocked mixtures of sodium and potassium feldsparsProceedings 16th Lunar and Planetary Science Conference ppD103ndashD115

Snyder G A Taylor L A and Patchen A 1999a Lunar meteoriteEET 96008 Part I Petrology and mineral chemistry Evidence oflarge-scale late-stage fractionation (abstract 1499) 30th Lunarand Planetary Science Conference CD-ROM

Snyder G A Neal C R Ruzicka A M and Taylor L A 1999bLunar meteorite EET 96008 Part II Whole-rock trace-elementand PGE chemistry and pairing with EET 87521 (abstract1705) 30th Lunar and Planetary Science Conference CD-ROM

Springer R K 1980 Geology of the Pine Hill intrusive complex alayered gabbroic body in the western Sierra Nevada foothillsCalifornia Summary Geological Society of America Bulletin 91381ndash385

Steele A M Colson RO Korotev R L and Haskin L A 1992Apollo 15 green glass Compositional distribution andpetrogenesis Geochimica et Cosmochimia Acta 564075ndash4090

Tanimizu M and Tanaka T 2002 Coupled Ce-Nd isotopesystematics and REE differentiation of the moon Geochimica etCosmochimica Acta 664007ndash4014

Taylor G J Warner R D Keil K Ma M S and Schmitt R A 1980Silicate liquid immiscibility evolved lunar rocks and theformation of KREEP In Proceedings of the Conference on thelunar highlands crust edited by Papike J J and Merrill R BNew York Pergamon Press pp 339ndash352

Taylor L A Nazarov M A Demidova S I and Patchen A 2001Dhofar 287 A new lunar mare basalt from Oman Meteoritics ampPlanetary Science 36A204

Thompson J B Jr 1982 Composition space An algebraic and

geometric approach In Characterization of metamorphismthrough mineral equilibria edited by Ferry J M WashingtonDC Mineralogical Society of America Reviews in Mineralogy101ndash31

Warren P H 1985 The lunar magma ocean concept Annual Reviewof Earth and Planetary Science 13201ndash240

Warren P H 1986 Anorthosite assimilation and the origin of the MgFe-related bimodality of pristine Moon rocks Support for themagmasphere hypothesis Proceedings 16th Lunar and PlanetaryScience Conference pp D331ndashD343

Warren P H 1993 A concise compilation of petrologic informationon possibly pristine nonmare Moon rocks AmericanMineralogist 78360ndash376

Warren P H and Kallemeyn G W 1989 Elephant Moraine 87521The first lunar meteorite composed of predominantly marematerial Geochimia et Cosmochimica Acta 533323ndash3300

Warren P H and Kallemeyn G W 1991b The MacAlpine Hills lunarmeteorite and implications of the lunar meteorites collectivelyfor the composition and origin of the Moon Geochimica etCosmochimica Acta 553123ndash3138

Warren P H and Kallemeyn G W 1991a Geochemical investigationof five lunar meteorites Implications for the composition originand evolution of the lunar crust Proceedings of the NIPRSymposium on Antarctic Meteorites 491ndash117

Warren P H and Kallemeyn G W 1993a Geochemical investigationof two lunar mare meteorites Yamato-793169 and Asuka-881757 Proceedings of the NIPR Symposium on AntarcticMeteorites 635ndash57

Warren P H and Kallemeyn G W 1993b The ferroan-anorthositicsuit the extent of lunar melting and the bulk composition of themoon Journal of Geophysical Research 985445ndash5455

Warren P H and Wasson J T 1977 Pristine nonmare rocks and thenature of the lunar crust Proceedings 8th Lunar and PlanetaryScience Conference 82215ndash2235

Yagi K and Takeshita H 1987 Impact of hornblende crystallizationfor the genesis of calc-alkalic andesites In Magmatic processesPhysicochemical principles edited by Mysen B O UniversityPark The Geochemical Society pp 183ndash190

Yanai K and Kojima H 1991 Varieties of lunar meteorites recoveredfrom Antarctica Proceedings of the NIPR Symposium onAntarctic Meteorites 470ndash90

554 T J Fagan et al

APPENDIX

Table A1 Results (mgg) of ICP-MS analyses from NWA 773ldquoClastrdquo Breccia

Run 1 Run 2 Mean Run 1 Run 2 Mean

Li 75 76 76 95 97 96Sc 266 269 268 397 388 393Ti 2852 2889 2870 5265 5080 5170V 81 83 82 134 131 132Cr 2297 2306 2300 2709 2613 2660Co 95 97 96 65 64 65Ni 210 217 214 121 124 122Cu 6 7 7 12 12 12Zn 11 11 11 8 9 9Ga 31 32 32 41 41 41Rb 18 19 18 34 34 34Sr 399 408 403 601 612 607Y 308 310 309 549 564 556Zr 164 171 167 242 250 246Nb 89 93 91 138 142 140Mo 025 032 028 026 032 029Cd 0045 0045 0045 0052 0054 0053Sn 06 06 06 226 190 208Sb 0009 0008 0009 0011 0008 0010Cs 0063 0061 0062 0150 0150 0150Ba 151 147 149 161 159 160La 82 79 80 141 138 140Ce 215 207 211 371 364 368Pr 290 276 283 501 489 495Nd 136 131 133 237 230 234Sm 395 378 387 696 677 686Eu 038 038 038 062 060 061Gd 457 444 450 816 796 806Dy 515 501 508 958 947 953Ho 112 108 110 210 205 207Er 299 286 293 568 553 560Yb 290 286 288 567 565 566Lu 043 041 042 083 082 083Hf 337 334 336 544 535 540Ta 037 038 037 063 063 063Th 130 126 128 231 230 231U 032 031 032 061 060 061

530 T J Fagan et al

one-fifth of the lunar near-side surface but only about 1 ofthe lunar crust (Head and Wilson 1992) Furthermore remotesensing studies show that the Apollo and Luna missionssampled a portion of the moon anomalously enriched inincompatible heat-producing elements (Jolliff et al 2000Lawrence et al 2000) The geochemically anomalous andspatially restricted nature of the areas sampled during theApollo and Luna missions results in a sample set thatalthough extraordinarily valuable cannot be consideredrepresentative of the lunar crust

In light of these limitations lunar meteorites provide animportant complement to the Apollo and Luna samplesObviously interpretation of the lunar meteorites is hinderedbecause we cannot specify a priori the precise location on themoon from which a given meteorite originates Lunarmeteorites may come from anywhere on the moon and thusare not necessarily restricted to a limited region of the near-side With continuing exploration of Antarctica and hotdeserts the number of identified lunar meteorites isincreasing to the point where geochemical patternscharacteristic of meteorites can be discussed and comparedwith systematics of the Apollo and Luna samples (Snyder etal 1999a Warrren and Kallemeyn 1991b Arai et al 2002)

In this paper we describe the lunar meteorite NorthwestAfrica (NWA) 773 document its lunar origin discuss itsimplications for petrogenesis of lunar mafic rocks and comparethis meteorite with geochemical patterns associated withspecific stages of magmatic evolution of the moon (Shearer andPapike 1999) The meteorite consists of two texturally distinctlithologies a dark gray fragmental regolith breccia and agreen two-pyroxene olivine gabbro (Fig 1) We argue that theolivine gabbro and clasts in the breccia record a complexigneous differentiation history The geochemistry of NWA 773is similar in some respects to other mafic lunar meteorites butdistinct from typical Apollo and Luna mare basalts (Snyder etal 1999b Shearer and Papike 1999)

ANALYTICAL METHODS

Petrography and Mineral Compositions

Three polished thin sections of NWA 773 were examinedusing petrographic microscopes Backscattered electron(BSE) images elemental X-ray maps and quantitativeanalyses of phases were collected using a Cameca SX-50electron microprobe at the University of Hawairsquoi and aCameca MBX electron microprobe at Northern ArizonaUniversity Two large-scale elemental maps of Na Mg Al SiP K Ca Ti Cr and Fe Ka were collected using a 15 keV 50nA focused electron beam with step sizes of 9 mm for onethin section and 18 mm for the other section The elementalmaps were combined using image processing software andwere used to estimate mineral modes (Hicks et al 20002002) Modal estimates were based on 13 times 105 counts from

approximately 81 mm2 from one thin section of the brecciaand 43 times 105 counts from 104 mm2 from two thin sections ofthe olivine gabbro Modes and mean mineral compositions(determined by electron microprobe analyses see below)were combined to provide an estimate of major elementalcomposition of the olivine gabbro Compositions of mineralsin the polymict breccia portion of NWA 773 vary over wideranges in different types of clasts thus the elementalcomposition of the breccia was not estimated by modalrecombination

Quantitative mineral compositions were determinedusing wavelength dispersive analyses based on well-characterized oxide and silicate standards A 15 keV voltageand peak and background counting times of 12 to 30 s wereused for all analyses but current and spot size varieddepending on the phase analyzed and the goal of the specificanalyses Most silicates and oxides were analyzed using afocused beam (~1 mm diameter) and 20 nA current Thecurrent was lowered to 10 nA for many feldspar and Ca-phosphate analyses A 10 nA beam rastering over an area ofapproximately 12 times 8 mm was used for analyses of glass inmelt inclusions a glass spherule and a fragment of regolithagglutinate We normalized oxide and silicate mineralformulae assuming that Ti and Cr are present as Ti4+ and Cr3+though we recognize that some Ti3+ and Cr2+ may be present

Bulk Elemental Composition

We initially obtained a small ~200 mg chip of NWA 773dominated by the breccia lithology with a small green clastsimilar to the olivine gabbro for whole-rock geochemicalanalysis We prepared two samples for geochemical analysisfrom this chip We separated an ~14 mg sample of pureolivine-gabbro-like material which we refer to as ldquoclastrdquo andthen ground and homogenized the remaining material as abreccia lithology sample An ~23 mg split of the breccialithology was taken for instrumental neutron activationanalysis (INAA) Subsequent to INAA on these samples wereceived a second ~325 mg chip of the olivine gabbro Thissample was ground and homogenized and an ~39 mg splitwas taken for INAA An ~20 mg split of the homogenizedpowder of the breccia was fused into a glass bead in an Aratmosphere following Brown (1977) for major elementanalysis via electron microprobe (FB-EMPA) A split of theolivine gabbro lithology failed to form a homogeneous glassbeadmdashquench crystals of olivine were ubiquitous on thesurface of the bead Analyses of the fused beads were done onthe JSC SX100 probe Analytical conditions were 15 kV and15 nA with a focused beam rastered over a 10 times 10 mm area

Samples standards and controls were sealed in puresilica glass tubes for INAA The INAA was done in twoirradiations using standard JSC procedures (Mittlefehldt1994) The breccia lithology and the clast sample wereirradiated at a flux of 55 times 1013 n cm-2 s-1 for 20 hr The






532 T J Fagan et al




























534 T J Fagan et al






















single mineral



zoned pyx







536 T J Fagan et al










Breccia Lithology








PhasePlagio-clasea

Plagio-claseb

K Ba feldspar

Plagio-clase

Plagio-clase

K Ba feldspar

Plagio-clase

Silica-rich glass

Silica-rich glass

Silica-rich glass

Silica-rich glass



fayalite granite

symplec-tite

symplec-tite





538 T J Fagan et al


























540 T J Fagan et al





























542 T J Fagan et al








Mass (mg) 3941 1446 2347 JSC Lit









NOBLE GASES



544 T J Fagan et al








181000plusmn 7000

20400plusmn 600

5470plusmn 160

2580plusmn 70

1293plusmn 013

237plusmn 04

527plusmn 005

221plusmn 003


192000plusmn 7000

22300plusmn 500

5960plusmn 160

2470plusmn 50

1289plusmn 013

234plusmn 03

527plusmn 004

225plusmn 003

lt 35 mm(1465 mg)

175000plusmn 7000

16900plusmn 500

5050plusmn 160

2240plusmn 50

1294plusmn 013

228plusmn 03

528plusmn 004

230plusmn 003



1540plusmn 40

3400plusmn 300

35plusmn 0

142plusmn 020

183plusmn 003

1350plusmn 30





DISCUSSION

Lunar Origin







Cosmogenic Solar










546 T J Fagan et al




















548 T J Fagan et al




















550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX









532 T J Fagan et al




























534 T J Fagan et al






















single mineral



zoned pyx







536 T J Fagan et al










Breccia Lithology








PhasePlagio-clasea

Plagio-claseb

K Ba feldspar

Plagio-clase

Plagio-clase

K Ba feldspar

Plagio-clase

Silica-rich glass

Silica-rich glass

Silica-rich glass

Silica-rich glass



fayalite granite

symplec-tite

symplec-tite





538 T J Fagan et al


























540 T J Fagan et al





























542 T J Fagan et al








Mass (mg) 3941 1446 2347 JSC Lit









NOBLE GASES



544 T J Fagan et al








181000plusmn 7000

20400plusmn 600

5470plusmn 160

2580plusmn 70

1293plusmn 013

237plusmn 04

527plusmn 005

221plusmn 003


192000plusmn 7000

22300plusmn 500

5960plusmn 160

2470plusmn 50

1289plusmn 013

234plusmn 03

527plusmn 004

225plusmn 003

lt 35 mm(1465 mg)

175000plusmn 7000

16900plusmn 500

5050plusmn 160

2240plusmn 50

1294plusmn 013

228plusmn 03

528plusmn 004

230plusmn 003



1540plusmn 40

3400plusmn 300

35plusmn 0

142plusmn 020

183plusmn 003

1350plusmn 30





DISCUSSION

Lunar Origin







Cosmogenic Solar










546 T J Fagan et al




















548 T J Fagan et al




















550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX























534 T J Fagan et al






















single mineral



zoned pyx







536 T J Fagan et al










Breccia Lithology








PhasePlagio-clasea

Plagio-claseb

K Ba feldspar

Plagio-clase

Plagio-clase

K Ba feldspar

Plagio-clase

Silica-rich glass

Silica-rich glass

Silica-rich glass

Silica-rich glass



fayalite granite

symplec-tite

symplec-tite





538 T J Fagan et al


























540 T J Fagan et al





























542 T J Fagan et al








Mass (mg) 3941 1446 2347 JSC Lit









NOBLE GASES



544 T J Fagan et al








181000plusmn 7000

20400plusmn 600

5470plusmn 160

2580plusmn 70

1293plusmn 013

237plusmn 04

527plusmn 005

221plusmn 003


192000plusmn 7000

22300plusmn 500

5960plusmn 160

2470plusmn 50

1289plusmn 013

234plusmn 03

527plusmn 004

225plusmn 003

lt 35 mm(1465 mg)

175000plusmn 7000

16900plusmn 500

5050plusmn 160

2240plusmn 50

1294plusmn 013

228plusmn 03

528plusmn 004

230plusmn 003



1540plusmn 40

3400plusmn 300

35plusmn 0

142plusmn 020

183plusmn 003

1350plusmn 30





DISCUSSION

Lunar Origin







Cosmogenic Solar










546 T J Fagan et al




















548 T J Fagan et al




















550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX







single mineral



zoned pyx







536 T J Fagan et al










Breccia Lithology








PhasePlagio-clasea

Plagio-claseb

K Ba feldspar

Plagio-clase

Plagio-clase

K Ba feldspar

Plagio-clase

Silica-rich glass

Silica-rich glass

Silica-rich glass

Silica-rich glass



fayalite granite

symplec-tite

symplec-tite





538 T J Fagan et al


























540 T J Fagan et al





























542 T J Fagan et al








Mass (mg) 3941 1446 2347 JSC Lit









NOBLE GASES



544 T J Fagan et al








181000plusmn 7000

20400plusmn 600

5470plusmn 160

2580plusmn 70

1293plusmn 013

237plusmn 04

527plusmn 005

221plusmn 003


192000plusmn 7000

22300plusmn 500

5960plusmn 160

2470plusmn 50

1289plusmn 013

234plusmn 03

527plusmn 004

225plusmn 003

lt 35 mm(1465 mg)

175000plusmn 7000

16900plusmn 500

5050plusmn 160

2240plusmn 50

1294plusmn 013

228plusmn 03

528plusmn 004

230plusmn 003



1540plusmn 40

3400plusmn 300

35plusmn 0

142plusmn 020

183plusmn 003

1350plusmn 30





DISCUSSION

Lunar Origin







Cosmogenic Solar










546 T J Fagan et al




















548 T J Fagan et al




















550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX




536 T J Fagan et al










Breccia Lithology








PhasePlagio-clasea

Plagio-claseb

K Ba feldspar

Plagio-clase

Plagio-clase

K Ba feldspar

Plagio-clase

Silica-rich glass

Silica-rich glass

Silica-rich glass

Silica-rich glass



fayalite granite

symplec-tite

symplec-tite





538 T J Fagan et al


























540 T J Fagan et al





























542 T J Fagan et al








Mass (mg) 3941 1446 2347 JSC Lit









NOBLE GASES



544 T J Fagan et al








181000plusmn 7000

20400plusmn 600

5470plusmn 160

2580plusmn 70

1293plusmn 013

237plusmn 04

527plusmn 005

221plusmn 003


192000plusmn 7000

22300plusmn 500

5960plusmn 160

2470plusmn 50

1289plusmn 013

234plusmn 03

527plusmn 004

225plusmn 003

lt 35 mm(1465 mg)

175000plusmn 7000

16900plusmn 500

5050plusmn 160

2240plusmn 50

1294plusmn 013

228plusmn 03

528plusmn 004

230plusmn 003



1540plusmn 40

3400plusmn 300

35plusmn 0

142plusmn 020

183plusmn 003

1350plusmn 30





DISCUSSION

Lunar Origin







Cosmogenic Solar










546 T J Fagan et al




















548 T J Fagan et al




















550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX






Breccia Lithology








PhasePlagio-clasea

Plagio-claseb

K Ba feldspar

Plagio-clase

Plagio-clase

K Ba feldspar

Plagio-clase

Silica-rich glass

Silica-rich glass

Silica-rich glass

Silica-rich glass



fayalite granite

symplec-tite

symplec-tite





538 T J Fagan et al


























540 T J Fagan et al





























542 T J Fagan et al








Mass (mg) 3941 1446 2347 JSC Lit









NOBLE GASES



544 T J Fagan et al








181000plusmn 7000

20400plusmn 600

5470plusmn 160

2580plusmn 70

1293plusmn 013

237plusmn 04

527plusmn 005

221plusmn 003


192000plusmn 7000

22300plusmn 500

5960plusmn 160

2470plusmn 50

1289plusmn 013

234plusmn 03

527plusmn 004

225plusmn 003

lt 35 mm(1465 mg)

175000plusmn 7000

16900plusmn 500

5050plusmn 160

2240plusmn 50

1294plusmn 013

228plusmn 03

528plusmn 004

230plusmn 003



1540plusmn 40

3400plusmn 300

35plusmn 0

142plusmn 020

183plusmn 003

1350plusmn 30





DISCUSSION

Lunar Origin







Cosmogenic Solar










546 T J Fagan et al




















548 T J Fagan et al




















550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX




538 T J Fagan et al


























540 T J Fagan et al





























542 T J Fagan et al








Mass (mg) 3941 1446 2347 JSC Lit









NOBLE GASES



544 T J Fagan et al








181000plusmn 7000

20400plusmn 600

5470plusmn 160

2580plusmn 70

1293plusmn 013

237plusmn 04

527plusmn 005

221plusmn 003


192000plusmn 7000

22300plusmn 500

5960plusmn 160

2470plusmn 50

1289plusmn 013

234plusmn 03

527plusmn 004

225plusmn 003

lt 35 mm(1465 mg)

175000plusmn 7000

16900plusmn 500

5050plusmn 160

2240plusmn 50

1294plusmn 013

228plusmn 03

528plusmn 004

230plusmn 003



1540plusmn 40

3400plusmn 300

35plusmn 0

142plusmn 020

183plusmn 003

1350plusmn 30





DISCUSSION

Lunar Origin







Cosmogenic Solar










546 T J Fagan et al




















548 T J Fagan et al




















550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX











540 T J Fagan et al





























542 T J Fagan et al








Mass (mg) 3941 1446 2347 JSC Lit









NOBLE GASES



544 T J Fagan et al








181000plusmn 7000

20400plusmn 600

5470plusmn 160

2580plusmn 70

1293plusmn 013

237plusmn 04

527plusmn 005

221plusmn 003


192000plusmn 7000

22300plusmn 500

5960plusmn 160

2470plusmn 50

1289plusmn 013

234plusmn 03

527plusmn 004

225plusmn 003

lt 35 mm(1465 mg)

175000plusmn 7000

16900plusmn 500

5050plusmn 160

2240plusmn 50

1294plusmn 013

228plusmn 03

528plusmn 004

230plusmn 003



1540plusmn 40

3400plusmn 300

35plusmn 0

142plusmn 020

183plusmn 003

1350plusmn 30





DISCUSSION

Lunar Origin







Cosmogenic Solar










546 T J Fagan et al




















548 T J Fagan et al




















550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX


















542 T J Fagan et al








Mass (mg) 3941 1446 2347 JSC Lit









NOBLE GASES



544 T J Fagan et al








181000plusmn 7000

20400plusmn 600

5470plusmn 160

2580plusmn 70

1293plusmn 013

237plusmn 04

527plusmn 005

221plusmn 003


192000plusmn 7000

22300plusmn 500

5960plusmn 160

2470plusmn 50

1289plusmn 013

234plusmn 03

527plusmn 004

225plusmn 003

lt 35 mm(1465 mg)

175000plusmn 7000

16900plusmn 500

5050plusmn 160

2240plusmn 50

1294plusmn 013

228plusmn 03

528plusmn 004

230plusmn 003



1540plusmn 40

3400plusmn 300

35plusmn 0

142plusmn 020

183plusmn 003

1350plusmn 30





DISCUSSION

Lunar Origin







Cosmogenic Solar










546 T J Fagan et al




















548 T J Fagan et al




















550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX









NOBLE GASES



544 T J Fagan et al








181000plusmn 7000

20400plusmn 600

5470plusmn 160

2580plusmn 70

1293plusmn 013

237plusmn 04

527plusmn 005

221plusmn 003


192000plusmn 7000

22300plusmn 500

5960plusmn 160

2470plusmn 50

1289plusmn 013

234plusmn 03

527plusmn 004

225plusmn 003

lt 35 mm(1465 mg)

175000plusmn 7000

16900plusmn 500

5050plusmn 160

2240plusmn 50

1294plusmn 013

228plusmn 03

528plusmn 004

230plusmn 003



1540plusmn 40

3400plusmn 300

35plusmn 0

142plusmn 020

183plusmn 003

1350plusmn 30





DISCUSSION

Lunar Origin







Cosmogenic Solar










546 T J Fagan et al




















548 T J Fagan et al




















550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX




544 T J Fagan et al








181000plusmn 7000

20400plusmn 600

5470plusmn 160

2580plusmn 70

1293plusmn 013

237plusmn 04

527plusmn 005

221plusmn 003


192000plusmn 7000

22300plusmn 500

5960plusmn 160

2470plusmn 50

1289plusmn 013

234plusmn 03

527plusmn 004

225plusmn 003

lt 35 mm(1465 mg)

175000plusmn 7000

16900plusmn 500

5050plusmn 160

2240plusmn 50

1294plusmn 013

228plusmn 03

528plusmn 004

230plusmn 003



1540plusmn 40

3400plusmn 300

35plusmn 0

142plusmn 020

183plusmn 003

1350plusmn 30





DISCUSSION

Lunar Origin







Cosmogenic Solar










546 T J Fagan et al




















548 T J Fagan et al




















550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX








DISCUSSION

Lunar Origin







Cosmogenic Solar










546 T J Fagan et al




















548 T J Fagan et al




















550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX




546 T J Fagan et al




















548 T J Fagan et al




















550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX













548 T J Fagan et al




















550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX












550 T J Fagan et al


CONCLUSIONS











REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX







REFERENCES





































552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX




552 T J Fagan et al

































































554 T J Fagan et al

APPENDIX





























554 T J Fagan et al

APPENDIX




northwest africa 773: lunar origin and iron-enrichment trend

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