annual review earth jadeite and tectonic

EA43CH04-Harlow ARI 29 April 2015 13:2

Jadeitites and Plate TectonicsGeorge E. Harlow,1 Tatsuki Tsujimori,2

and Sorena S. Sorensen31Department of Earth and Planetary Sciences, American Museum of Natural History,New York, NY 10024-5192; email: [email protected] Memorial Laboratory, Institute for Study of the Earths Interior, OkayamaUniversity, Misasa, Tottori 682-0193, Japan; email: [email protected] of Mineral Sciences, Smithsonian Institution, Washington, DC 20013-7012;email: [email protected]

Annu. Rev. Earth Planet. Sci. 2015. 43:10538

First published online as a Review in Advance onJanuary 2, 2015

The Annual Review of Earth and Planetary Sciences isonline at earth.annualreviews.org

This articles doi:10.1146/annurev-earth-060614-105215

Copyright c 2015 by Annual Reviews.All rights reserved

Keywords

high-pressure/low-temperature rocks, uid-mediated transport,serpentinite melange, subduction processes

Abstract

Jadeitite is a relatively rare, very tough rock composed predominantlyof jadeite and typically found associated with tectonic blocks of high-pressure/low-temperature metabasaltic rocks (e.g., eclogite, blueschist) inexhumed serpentinite-matrixmelanges. Studies over the past20 years haveinterpreted jadeitite either as the direct hydrous uid precipitate from sub-duction channel dewatering into the overlying mantle wedge or as the meta-somatic replacement by such uids of oceanic plagiogranite, graywacke, ormetabasite along the channel margin. Thus, jadeitites directly sample andrecord uid transport in the subduction factory and provide a window intothis geochemical process that is critical to a major process in the Earth sys-tem. They record the remarkable transport of large ion lithophile elements,such as Li, Ba, Sr, and Pb, as well as elements generally considered morerefractory, such as U, Th, Zr, and Hf. Jadeitite is also the precious form ofjade, utilized since antiquity in the form of tools, adornments, and symbolsof prestige.

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Jadeitite: a rockcomposed primarily ofclinopyroxene withjadeite content,typically from 80 to100 mol%; all jadeitejades are jadeitites

Jadeite jade: the formof jade composedprincipally (more than90%) ofclinopyroxene ofprimarily jadeitecomposition(NaAlSi2O6)

Serpentinite: a rockcomposed principallyof serpentine minerals(antigorite and/orlizardite) typicallyformed from thehydration of peridotite

Peridotite: a rockcomposed of >40%olivine and 90% jadeite, hasbeen revered for its extraordinary toughness as a tool stone even prior to Neolithic time. Themost noteworthy occurrence is in the Kachin Hills of northern Myanmar (formerly Burma), theworldsmajor source for this precious rock, where it is found in serpentinite boulder conglomeratesand as veins and tectonic blocks in serpentinite. Although initially interpreted as an igneousintrusion into peridotite (e.g., Bleeck 1908), a melt of jadeite composition dees any recognizedmodel of melting on Earth. Thus, some other process, such as hydrothermal metasomatism ofoceanic plagiogranite (trondhjemitic to dacitic igneous rocks with dominant albite and quartz),was suggested by Coleman (1961, 1980) in connection with jadeitite fromCalifornia and expandedupon by Dobretsov (1984) in relationship to ophiolites (the term serpentinite melanges shouldhave been used, as discussed below) of the West Sayan, Khakassia, Russia, and the Polar Urals,Russia. In the intervening 30 years, great progress has been made in both the understandingand the discovery of jadeitite. The context of jadeitite as a uid crystallizationtometasomaticproduct in the context of the channel-wedge boundary of a fossil subduction system, exhumed inserpentinite-matrix melange, is well established (e.g., Tsujimori & Harlow 2012, Harlow et al.2014). Moreover, during this period, the number of described occurrences has expanded fromaround 8 to more than 16, with more likely on the way.

The purpose of this review is to present the context and contemporary understanding ofjadeitites as hydrous uid precipitates and metasomatic modications generated by dewateringand dissolution in the subduction channel of subduction systems, terminated by some collisionaltectonic event that exhumed the channel boundary as a serpentinite melange. As a record of uid-mediated transport along and through the channel boundary and of the tectonics of melangeexhumation, jadeitite and its associated lithologies are important to a fuller understanding of thesubduction process and its relationship to arc volcanism via uxing, to geochemical cycles, andto the Earth system. Some of the wording here derives from the recent review by Harlow et al.(2014). Mineral abbreviations throughout this review are mostly after Whitney & Evans (2010)and are summarized in Table 1.

2. JADEITITE AND JADE

The words jade and jadeite were originally synonymous, derived from the Spanish description ofthe ornamental and talismanic stone used by theAztecs inwhat is nowMexico: piedra de yjada (stone

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Table 1 Minerals, abbreviations, and formulae

Abbreviation Mineral name Formula NotesAb Albite NaAlSi3O8 Feldspar groupAe Aegirine NaFe3+Si2O6 A pyroxene componentAnl Analcime Ideally NaAlSi2O6H2O Atg Antigorite Approximately Mg3Si2O5(OH)4 Serpentine group; stable at higher temperaturesBrc Brucite Mg(OH)2 Chr Chromite FeCr2O4 A spinel componentChl Chlorite Clinochlore: Mg5Al(AlSi3O10)(OH)8

Chamosite: Fe2+5Al(AlSi3O10)(OH)8Sudoite: Mg2Al3(AlSi3O10)(OH)8

A mineral group; the most common components arelisted

Cpx Clinopyroxene GenerallyNaM3+Si2O6CaM2+Si2O6

Pyroxenes with monoclinic crystal structure

Czo Clinozoisite Ca2Al3(SiO4)3(OH) Epidote groupDi Diopside CaMgSi2O6 A pyroxene componentEp Epidote Ca2Fe3+Al2(SiO4)3(OH) Gln Glaucophane Na2(Mg3Al2)Si8O22(OH)2 Amphibole groupGrs Grossular Ca3Mg2(SiO4)3 Garnet groupGrt Garnet M2+3N3+2(SiO4)3 Generic silicate garnetHd Hedenburgite CaFeSi2O6 A pyroxene componentJd Jadeite NaAlSi2O6 A pyroxene componentKtp Katophorite Na(CaNa)(Mg4Al)AlSi7O22(OH)2 Amphibole groupKy Kyanite AlSi2O5 High-pressure polymorphLz Lizardite Mg3Si2O5(OH)4 Serpentine group; stable at lower temperaturesLws Lawsonite CaAl2Si2O7(OH)2H2O Ms Muscovite KAl(AlSi3O10)(OH)2 Mica groupNe Nepheline (Na,K)AlSiO4 Ol Olivine (Mg,Fe)2SiO4 Omp Omphacite Ideally (CaNa)[(Mg,Fe)Al](Si2O6)2 Pyroxene groupOpx Orthopyroxene (Mg,Fe)SiO3 Pg Paragonite NaAl2(AlSi3O10)(OH)2 Mica groupPh Phengite KAl2(AlSi3O10)(OH)2 A varietal of muscovite, formed at high pressure, in

which there is a considerable, perhaps 10%,Tschermaks exchange: Mg + Si for viAl + ivAl(superscripts denote coordination number in thecrystal structure)

Pmp Pumpellyite-(Mg) Ca2MgAl2(Si3O11)(OH)2H2O Most common; -(Fe2+), -(Fe3+), and -(Mn) speciesalso occur

Qz Quartz SiO2 Rt Rutile TiO2 Tr Tremolite Ca2(Mg,Fe)5Si8O22(OH)2 Ttn Titanite CaTiSiO5 Also known as spheneZrn Zircon ZrSiO4

www.annualreviews.org Jadeitites and Plate Tectonics 107

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Melange: fromFrench; a lithologicalunit of mixed rocktypes as blocks in ahighly deformedne-grained matrix,formed along a fault,typically at the upperboundary of asubduction channel

Jade: the term used inWestern cultures fortwo monomineralicrocks, jadeite jade andnephrite, that haveextreme fracturetoughness and are usedfor fashioning toolsand ornaments

Nephrite: the formof jade composedprincipally of amicrocrystallineintergrowth of feltedamphibole grains,primarily of tremolite[Ca2(Mg,Fe)5Si8O22-(OH)2] composition

Porphyroblasts:larger grains of amineral within agenerally ner-grainedmetamorphic rock

of the side or loins), worn to ease pain in the side or stomach (see Foshag 1957,Mottana 2012). Jadewas a mistranslation into French (Buffon 1749, 17831788) that persists to this day. The essenceof this New World stone was later determined to be the mineral jadeite (Damour 1881), but bythat time it had already been confused with the green stone most familiar from China, Wernerslapis nephriticus or nephrite [the massive form of tremolite, Ca2(Mg,Fe)5Si8O22(OH)2; Damour1846]. Both forms of jade were revered as tool stones because of their toughness and suitabilityfor fashioning axes (celts), chopping stones, and hammers, certiably during the Neolithic butprobably as early as the Paleolithic (before 35000 BCE). Subsequently, the more attractive coloredversions of jade were transformed into talismanic and artistic forms to convey well-being, power,and status. A jade culture existed in a variety of places but was retained only in Southeast Asia,although the stone is now appreciated more widely via archaeology and artistic culture (Figure 1).

Nonetheless, there is an important geological connection to the archaeological legacy: Jadeobjects were known prior to themodern knowledge of their sources. This connection has aided thediscovery and recognition of new sources of jadeitite.Maya jadeite jade was recognized long beforethe identication of the source area along theMotagua River ofGuatemala (Foshag&Leslie 1955,McBirney et al. 1967). Our own work later greatly magnied the footprint of Guatemalan jadeititeand its context (Harlow 1994, Harlow et al. 2011, and citations therein). The recognition of Tainojades in eastern Cuba eventually spurred the recognition of the jadeitites of Sierra del Convento(Garca-Casco et al. 2009, Cardenas-Parraga et al. 2010), and in a reverse manner, the Ro SanJuan complex jadeitites led to the sourcing of many Dominican Republic jades (Knippenberg et al.2012; Schertl et al. 2012, 2014). One of the most recent putative discoveries is an unusual jadeititefrom the Torare River area of Papua, Indonesia, that was tracked from a jade gouge discovery onEmirau Island in the Bismarck Archipelago, Papua New Guinea, via rock specimens preservedat Utrecht University by C.E.A. Wichmann in 1893 (Harlow et al. 2012a,b). There are manyjadeite jade objects from Europe, some of which have been tracked to the Monviso metaophiolitecomplex, western Italian Alps, Italy (e.g., Compagnoni & Rolfo 2003); however, other potentialsources, such as the Queyras region of the French Alps and the Voltri Massif, western Alps, Italy,continue to be examined for potential (see Harlow et al. 2014). The point is that jade artifacts canshow the way toward geological sources yet to be discovered. Jadeitite has been routinely missedin regional geological surveys, but because our forebears were cognizant of the potential utility ofrocks for tools, we can take advantage of their discoveries in our search for jadeitite.

Jadeitite, sensu stricto, is a rock consisting predominantly of jadeitic pyroxenethat is,>90 vol% pyroxene with on average at least 80 mol% jadeite, a clinopyroxene with end-member composition NaAlSi2O6. Jadeitic pyroxene typically occurs in a solid solution that ismostly binary toward diopside (CaMgSi2O6), with lesser hedenbergite (CaFe2+Si2O6) and ae-girine (NaFe3+Si2O6), except for rare occurrences where jadeite-aegirine compositions are found(e.g., Papua; Harlow et al. 2012a,b). Practical denitions may be based on the term jadeitite modi-ed by another mineral for porphyroblasts, such as garnet, or for interbanding with glaucophane,phengite, or pumpellyite. Then there is the useful Russian-origin term apojadeitite (i.e., formedfrom jadeitite), which denes partially retrogressed or altered rocks typically containing veins orintergranular accumulations of albite, analcime, nepheline, diopsidic-acmitic (aegirine-rich) py-roxene, tremolite, etc. In some places, apojadeitite is found more commonly than jadeitite, andtrue jadeitite deposits usually contain apojadeitite.

3. LITHOLOGICAL AND GEODYNAMIC SETTING

The common thread of all jadeitite occurrences is their association with serpentinite-matrixmelanges bearing other rocks or blocks with high-pressure/low-temperature (HP/LT ) mineral


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a b

c

Figure 1(a) Jadeite jade incense burner; China (Myanmar jade); late nineteenth century; 18 cm high(AMNH-MinCol. 44032, courtesy of American Museum of Natural History and Van Pelt Photographers).(b) Olmec jadeite jade celt; Miahuatlan, Oaxaca, Mexico; ca. 15001400 BCE; 10.5 cm long(AMNH-AnthroCol. 30/11518, courtesy of the Division of Anthropology, American Museum of NaturalHistory, staff photo). (c) Jadeite jade magatamas from the second tomb of Sawano; Nara Prefecture, Japan;ca. 250400 CE; largest 3 cm long (courtesy of the Museum, Archaeological Institute of Kashihara, NaraPrefecture). Panel c modied with permission from Harlow et al. (2014).

assemblages. By this we mean the context of serpentinite from a convergent or transpressional set-ting that reects the exhumation of a former mantle wedge boundary above a subduction channel.Unfortunately, massive serpentinites of this afnity have routinely been described as portions ofan ophiolite. We consider this practice problematic, as ophiolites, even when not preserved withthe major segments of their marine or oceanic setting, are generally characterized tectonically byobductionoverthrusting onto an oceanic marginas opposed to exhumation from HP/LTconditions produced in a subduction channel. This origin is routinely reected in the lack of ahigher-T serpentinite polytype (antigorite) in true ophiolites except at their bases and the lack ofassociated HP/LT lithologies. The confusion may be increased by a not-too-unusual association


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P-type jadeitite:jadeitite crystallizeddirectly from ahydrous uid asvein-llings orovergrowths on otherrocks

R-type jadeitite:a metasomaticreplacement ofanother rock, such as asedimentary rock (e.g.,graywacke) or anigneous rock [e.g.,trondhjemite ortonalite (mostly sodicfeldspar + quartz)]

Mesozoic and Cenozoic (251 Mapresent) orogensPaleozoic (542251 Ma) orogens

Neoproterozoic (1 Ga542 Ma) orogensMesoproterozoic and older (>1 Ga) orogens

Jadeitite deposits Plate boundaries

Figure 2World map of jadeitite occurrences and tectonic settings. Continental crust ages are modied after Tsujimori et al. (2006b). Figuremodied with permission from Stern et al. (2013).

of paired melange-ophiolite occurrences: for example, the Baja Verapaz and Sierra de Santa Cruzultramacs (ophiolitic) north of the Northern Motagua melange (NMM) in Guatemala (Harlowet al. 2011, Flores et al. 2013), the Moa-Barracoa ophiolite north of the Sierra del Conventomelange in eastern Cuba (Garca-Casco et al. 2009), and the Gaspar Hernandez serpentinite(ophiolitic) and the Arroyo Sabana and Jagua Clara melanges in the Dominican Republic (Draperet al. 1991, Schertl et al. 2012). Distinguishing the serpentinite association is important for inter-pretation and exploration (Harlow & Flores 2011, Harlow et al. 2014).

The occurrence of jadeitite has been extensively reviewed (e.g., Harlow & Sorensen 2005;Harlow et al. 2007, 2014). More than 40 years after Colemans (1971) recognition of 6 purejadeite pod localities, 19 jadeitite localities have been reported in four Phanerozoic orogenicbelts (Caribbean; circum-Pacic; Alps/Himalayas; Uralides and Central Asia/Altaids), excludingxenoliths in kimberlitic pipes (Figure 2, Table 2). Except for the xenoliths, these lie withinserpentinite-matrix melanges, with fragments of oceanic crust and HP/LT metamorphic rocks,along major transform or thrust faults cutting the paleo-forearc or accretionary wedge. Consider-ing these worldwide occurrences, it is clear that serpentinite exhumation and melange formationare important for the preservation of jadeitite. These particular exhumation processes may alsoexplain the rareness of jadeitite occurrences.

On the basis of possible jadeitite formation models, Yui et al. (2010) used the terms veinprecipitation and metasomatic replacement for different jadeitite origins; Tsujimori & Harlow(2012) then classied the two types as P-type and R-type, respectively. Precipitated jadeitite doesnot contain evidence of a protolith and thus shows no evidence of isochemical transformation or


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Tab

le2

Sum

mar

yof

jade

itit

es(t

ypes

and

ages

)and

asso

ciat

edm

afic

HP/

LT

met

amor

phic

rock

s

Loc

alit

yT

ype

Pro

tolit

hag

eJa

deit

ite

form

atio

nR

ecry

stal

lizat

ion

orco

olin

gA

ssoc

iate

dm

afic

HP/

LT

rock

sM

etam

orph

icag

eC

arib

bean

Nor

ther

nM

otag

uamelan

ge,G

uatemalaa

PS

NA

Zrn

:98

95M

aPh:

776

5M

aEp-

Gln

eclogite,G

rtam

phibolite

Sm-N

d:15

912

6M

a(eclog

ite),Zrn

:76M

a(eclog

itein

Chu

acus

k )So

uthe

rnM

otag

uamelan

ge,G

uatemalab

PS,R

?N

AZrn

:154

Ma

Ph:

125

113M

aLwsec

logite,L

wsblue

schist

Sm-N

d:14

413

2M

a(eclog

ite)

Sier

rade

lCon

vent

o,Cub

acPS

NA

Zrn

:108

107

Ma

NA

Ep-

Grt

amph

ibolite

,tron

dhjemiti

cEpgn

eiss,

blue

schist

Zrn

:113

Ma(amph

ibolite

)

Ro

SanJu

anco

mplex

,Dom

inican

Rep

ublic

dPB

Zrn

:139

Ma

Zrn

:115

Ma

Zrn

:93M

aEclog

iteLu-

Hf:10

4M

a(eclog

ite)

PB,R

Zrn

:113

Ma

Zrn

:117

Ma

(cor

e),7

7.6M

a(rim

)

NA

Lwsblue

schist,G

rt-O

mp

blue

schist

Rb-

Sr:8

0,62

Ma(b

luesch

ist)

Cir

cum

-Pac

ific

Itoiga

wa-Omi,

sout

hwestJ

apan

ePS,R

NA

Zrn

:520

Ma

Ph:

340

320M

aEp-

Gln

eclogite,E

pblue

schist,E

p-Grt

amph

ibolite

,metag

abbr

o

Ph:

340

320M

a

Oya

-Wak

asa,

sout

hwestJ

apan

PS

NA

Early

Paleo

zoic

NA

Lws-Pmpblue

schist,E

pblue

schist,a

mph

ibolite

/metag

abbr

o

Ph:

280M

a(sch

ist),H

bl:

470

440M

a(E

pam

phibolite

,metag

abbr

o)Osaya

ma,

sout

hwest

Japa

nfPS,R

Zrn

:523

488

Ma

Zrn

:521

451

Ma

NA

Lwsblue

schist,E

pblue

schist,

Ep-

Gln

eclogite

Ph:

320M

a

Nishiso

nogi,K

yush

u,Japa

ngR

Zrn

:142

131

Ma

Zrn

:82M

aN

AEpblue

schist

Ph:

907

5M

a

Tor

areRiver

,Pap

ua,

Indo

nesia

PN

ACre

tace

ous

Paleo

gene

?N

AAmph

ibolite

,bluesch

ist?

NA

Ust-B

elay

a,Chu

kotka,

Rus

sia

PS

Early

Paleo

zoic

NA

NA

Grt

amph

ibolite

,bluesch

ist

NA

New

Idria,

Fran

ciscan

complex

,Califo

rnia

PS

NA

Cre

tace

ous?

NA

Lwsblue

schist,E

pec

logite,

Grt-C

pxam

phibolite

Hbl:1

10M

a(G

rtam

phibolite

)

WardCre

ek,

Fran

ciscan

Com

plex

,Califo

rnia

PB

NA

Cre

tace

ous?

NA

Lwsblue

schist,P

mp-

Ep

blue

schist,L

ws-Ep-

Gln

eclogite

Ph:

120M

a(b

luesch

ist)

(Con

tinue

d)


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Tab

le2

(Con

tinu

ed)

Loc

alit

yT

ype

Pro

tolit

hag

eJa

deit

ite

form

atio

nR

ecry

stal

lizat

ion

orco

olin

gA

ssoc

iate

dm

afic

HP/

LT

rock

sM

etam

orph

icag

eA

lps/

Him

alay

asSy

rosan

dTinos

,Cyc

lade

s,Gre

eceh

PS,R

SZrn

:80M

a(in

deba

te)

Zrn

:80M

a(in

deba

te)

NA

Ep-

Gln

eclogite

Zrn

:52M

a,Ph:

524

3M

a

Mon

viso

,Western

Alps

RS

Zrn

:163

Ma

Eoc

ene?

NA

Lwsec

logite

Zrn

:163

Ma(relic),45

Ma

(metam

orph

ic)

Sork

han,

Iran

PN

ACre

tace

ous?

NA

Lwsblue

schist

Ph:

908

0M

aJade

MineTract,

Mya

nmar

iPS,R

SZrn

:163

Ma

Zrn

:158

,147

,12

2,77

Ma

NA

Epblue

schist

Ph:

80M

a(eclog

ite),30

Ma

(bluesch

ist)

Ura

lides

Voika

r-Sy

nins

ky,P

olar

Urals,R

ussiaj

PS

Early

Paleo

zoic?

Zrn

:404

Ma

Zrn

:378

,368

Ma

Epam

phibolite

(metag

abbr

o),

blue

schist/eclog

iteZrn

:500

Ma(amph

ibolite

),36

035

5M

a(eclog

ite)

Cen

tral

Asi

a/A

ltai

dsBor

usRan

ge,W

est

Saya

n,Rus

sia

PS,R

SN

AEarly

Paleo

zoic?

NA

Eclog

iteZrn

:540

520

Ma

Ken

terlau

-Itm

urun

da-

Ark

harsu,

East

Kaz

akhs

tan

PS

NA

Zrn

:450

Ma

NA

Grt

amph

ibolite

,bluesch

ist

Zrn

:450

Ma

Abb

reviations

:Hbl,h

ornb

lend

eK-A

rag

e;H

P/LT,h

igh-

pressu

re/low

-tem

peratu

re;N

A,n

otav

ailable;

Ph,

phen

gite

K-A

r(o

r40Ar/

39Ar)

age;

Sm-N

d,Sm

-Ndminer

alisoc

hron

age;

Zrn

,zirco

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bag

e.Se

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able

1fo

rminer

alna

meab

brev

iatio

ns.

Refer

ence

sfo

rda

ting:

a Yui

etal.(20

10,2

012),F

lore

set

al.(20

13);

bFu

etal.(20

10),Fl

ores

etal.(20

13);

c Garca-Casco

etal.(20

09);

dSc

hertle

tal.(201

2),H

ertw

iget

al.(20

13);

e Kun

ugiza&

Got

o(201

0);f

Tsu

jimor

ieta

l.(200

5);g

Mor

ieta

l.(201

1);h

Fuet

al.(20

10,2

012);iSh

ieta

l.(200

8),Q

iuet

al.(20

09),Yui

etal.(20

12),Q

ieta

l.(201

4);jSh

atsk

yet

al.(20

00),Glodn

yet

al.(20

03,

2004

),M

enget

al.(20

11).

k Datefrom

eclogite

inth

ead

jace

ntChu

acus

gneisses

(Martens

etal.2

012).A

llot

herre

fere

nces

aregive

nin

Tsu

jimor

i&H

arlow

(201

2).


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Protolith: theoriginal type of rock,such as basalt, prior tometamorphism (e.g.,to an eclogite orblueschist) ormetasomatism

Blueschist: anHP/LT metamorphicrock formed frombasalt by hydrationand dominated by theblue amphiboleglaucophane; also thefacies, or P-T region,for blueschists

Omphacitite: a rockcomposed principallyof clinopyroxene ofomphacitecomposition,nominally(CaNa)[(Mg,Fe)Al]-(Si2O6)2 and a varietyof jade

pseudomorphic replacement of any precursor rocks. The pervasive evidence for crystallizationfrom a uid includes jadeite grains that host abundant uid inclusions (dominated by two-phasehydrous uid, often in the cores of crystals); small preserved areas or veins of cavity lling, typicallywith oscillatory zoned jadeite prisms; and, inmany cases, combinations of these features in brittlelydeformed/healed microtextures suggestive that the jadeitite ultimately formed in open veins butsuffered severe deformation. These features have been revealed in colorful detail with cathodo-luminescence microscopy, because low-Fe jadeite displays an array of colors documenting oftensubtle changes in composition (Figure 3). Most jadeitites belong to this P-type, and they are con-sidered to have precipitated directly from a Na-Al-Si-rich aqueous uid in some cavity, crack, orfracture in serpentinized peridotite or a HP/LT metamorphic rock. In contrast, replacive jadeititepartially preserves textural, mineralogical, or geochemical evidence of a preexisting protolith, suchas plagiogranite or metagraywacke-like rock. Harlow et al. (2014) expanded this classication witha differentiation based on where the jadeitite was hosted (i.e., where the precipitate formed): PS-type jadeitite is hosted in ultramac (serpentinite) rock and PB-type jadeitite in mac (blueschist)rock. This distinction has potential importance for the source of the crystallizing uid and itssolute load (see below).

3.1. Where Jadeitites Form

There are few occurrences where jadeitite appears to remain in its formation setting, or nearlyso, as the preponderance of jadeitite associations occur as blocks in serpentinite melanges or ero-sional accumulations in drainages. The classic occurrence of a supposed dike hosted in ultramacat Tawmaw, Myanmar (Figure 4), was a major reason for inferring an igneous origin as an albitegranite subsequently modied by desilicication (Bleeck 1908, Chhibber 1934). Two other in-teresting aspects of this occurrence are (a) the appearance of jadeitite at the center or core of thelayer and albitite toward the margin and (b) the asymmetry of the boundaries with the host ultra-mac, with an amphibole-dominant rock (mostly sodic amphiboles) at the base and a chlorite-richboundary layer on the hanging wall (essentially a blackwall reaction boundary). A similar associa-tion of jadeitite and albitite or apojadeitite has been described in the Levoketchpel deposit, PolarUrals (Fishman 2006; see also Dobretsov 1984), but in the veins of the Pusyerka deposit of theSyum-Keu complex, also in the Polar Urals, no albite is found and the boundary between jadeititeand ultramac is a phlogopite-anthophyllite lithology (Fishman 2006, Meng et al. 2011). Anothercontact has been reported in the Sierra de Las Minas, Guatemala, in which jadeitite is boundedby albitite adjacent to a meta-ultramac (chlorite-actinolite blackwall) and then a massive serpen-tinite (Sorensen et al. 2010). In all of these cases there is a mixture of primary jadeitite vein-likebodies, with or without an albitite or apojadeitite outer boundary layer, separated from the hostultramac by an amphibole rock or a chlorite-actinolite blackwall.

Jadeitite in contact with metabasite has been found in several places. In the Borus Mountains,West Sayan, Dobretsov (1984) interpreted the jadeitite as a metasomatic replacement: Rims ofeclogite blocks are replaced by omphacitite and then surrounded by small bodies of jadeitite,like a necklace, in the sheared serpentinite matrix. However, no relics of eclogite were describedin the jadeitite, so replacement is not absolutely clear. A similar occurrence was described forjadeitite from Syros, Cyclades, Greece, in which jadeitite appears to ll fractures in eclogiteblocks, an interpretation supported by the lack of relict garnet (Brocker & Keasling 2006). Anigneous protolith to the jadeitite was ruled out by the presence of HP inclusions in zircon in thejadeitite. Jadeitite has been found as concordant layers in blueschist in the Ro San Juan complexmelange, Dominican Republic, and as jadeite-quartzite or jadeite-lawsonite-quartzite mostly indiscordant tension gashes (Schertl et al. 2012); the jadeitites (sensu stricto) may be R- or P-type,


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aa bb

cc dd

ee ff

gg hh

~1 mmfor allimages

Figure 3Cathodoluminescence images of jadeitites. (a) American Museum of Natural History (AMNH) Specimen 104278; Ketchpel River, PolarUrals, Russia. (b) National Museum of Natural History (NMNH) Specimen 112701; Myanmar. (c) AMNH Field Number 01GSn6-13(Virginia Sisson); Guatemala. (d ) NMNH Specimen 94303; Myanmar. (e) AMNH Field Number MVJ84-9D (George Harlow);Guatemala. ( f ) NMNH Specimen 105860; Japan. ( g) AMNH Field Number MVE02-3-1 (Sorena Sorensen); Guatemala. (h) NMNHSpecimen 113778-1; California. All specimens were irradiated at 20 kV and 0.5 mA. The images in panels c and g were collected by anOlympus CCD camera using MagnaFire 2.0 software; the others are scanned emulsion images. All panels show the growth of extremelyidioblastic grains, oscillatory zoning, and apparent inlling of uid-lled spaces; panels a, b, and f also show apparent resorption andovergrowth features. Panel h additionally shows grain-size reduction and the entrapment of brecciated vein-forming grain fragmentsalong a sheared surface that cuts an earlier-formed vein. Figure modied with permission from Harlow et al. (2014).


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Serpentinite

Chlorite

Albitite

Jadeitite

Eckermannite-glaucophane amphiboliteEckermannite-glaucophane amphibolite

Schistoseamphibolite

inclusions

Albitite

Serpentinite

Figure 4Diagram of contact relationships of the jadeitite dike at Tawmaw, Myanmar, after gure 3 from Bleeck(1908). No dimensions were given in that source, but other sources (e.g., Chhibber 1934, Hughes et al.2000) indicate that the width can vary between 1.5 and >50 m and the length can exceed 1 km. Thedescribed pinching and swelling of these dikes suggest considerable tectonic deformation.

as work continues on these samples. However, the clear distinction here and at a couple of otheroccurrences (see Harlow et al. 2014) is that uid-crystallized jadeite occurs without the immediateproximity of an ultramac host. This feature led to their classication as either RB- or PB-typejadeitite.

3.2. Estimating P-T Conditions of Jadeitite Crystallization

Estimating P-T conditions for a rock that is nearly monomineralic relies on small variations incomposition, associated minerals that are minor and not developed in every jadeitite body orlocality, and techniques other than phase equilibria (e.g., coexisting rocks). Tsujimori & Harlow(2012) have reviewed the available information in detail, so only a general synopsis is providedhere. Harlow (1994) used the reactions Anl = Jd+H2O, Ab = Jd+Qz, and 4Lws+ 2Jd = Ab+Pg + 2Czo + 6H2O (with lowered activities of some components) to pose a possible limit on theupper P-T stability of quartz-free jadeitite (and when albite may be secondary) of 1.4 GPa and450C (Figure 5a). The presence of jadeite and the absence of quartz yield a lower limit forP estimates, fundamentally limited by either the reaction Anl = Jd + H2O in the presence of


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e

p

Stability limitsLwsPgRtOmpAmphiboleA[Na][Na]

Contourlines

B0.70.7

0.6

0.5

0.5

0.4

0.70.80

.9

0.9

RSJC1

SMM-

ens

SC

SMM

SMM

-cg

RSJC

2

IR

P (G

Pa)

T (C) T (C)

Depth (km

)

GR

DiaGr

CoeQz

Wet

tona

lite

solid

us

Wet granite solidus

Jd + Qz

Ab

Jd

Ab + Ne

Jd + H20= Anl An

lAb

+ Ne

SW Ja

pan

slab

surfa

ce

SW Ja

pan

slab s

urfa

ce

AM

Pg +

Czo +

Qz +

H 2O

Pg +

Czo +

Qz +

H 2O

Lws +

Jd

Lws +

Jd

Lws +

Ab

Lws +

Ab

a bb

Wet ja

deiti

te

solid

us

Atg out

NMM

Atg +

Brc

Fo +

H 2O

Fo +

H 2O

MNV

4.0

120

80

40

0

3.0

2.0

200 400 300 400 500 600600 800 1,000

1.0

P (G

Pa)

4.0

3.0

2.0

1.0

0

88

86

76

80

82

82

Ky-JDKy-JD

Pg-JDPg-JD

2Cpx-JD2Cpx-JD

Tar-JDTar-JD

Lws-JDLws-JD

Ky-JD Kyanite jadeititeLws-JD Lawsonite jadeitite

Pg-JD Paragonite jadeititeTar-JD Taramite jadeitite

2Cpx-JD Two-pyroxene jadeitite

p Pumpellyite stabilitye Epidote-group mineral stability

EAEAEA

GSGSGS

Amp-ECAmp-ECAmp-EC

Ep-ECEp-ECEp-EC

Dry-ECDry-ECDry-EC

Lws-ECLws-ECLws-EC

BSBSBSHGR

NE Japan slab surf

ace

78

78 80 80

82

8486

84

92

92

92

92

90

90

84

Jd + Qz

Ab

Jd

JdAnl

Ab + Ne

0.3

0.4

0.4

0.5

0.5

0.6

0.6

0.7

0.8

0.9

0.7 0.8 0.9

0.4Anl

Ab +

Ne

Ab +

Ne

IR IranMNV Monviso complex, Italian Alps

NMM Northern Motagua mlange, GuatemalaRSJC1, RSJC2 Ro San Juan complex, Dominican Republic

SC Sierra del Convento complex, CubaSMM Southern Motagua mlange, Guatemala

Jadeitite mineralogiesLocations

Minerals

Jd JadeiteAb Albite

Brc Brucite

Anl AnalcimeAtg Antigorite

Czo Clinozoisite Omp Omphacite

Lws LawsoniteNephelineNe

Gr Graphite

Pg ParagoniteRt RutileQz Quartz

SMM-cg SMM, Carrizal GrandeSMM-ens SMM, La Ensenada

Coe CoesiteDia Diamond

Fo Forsterite

Metamorphic facies

GS GreenschistEA Epidote amphibolite

AM AmphiboliteGR Granulite

BS BlueschistLws-EC Lawsonite eclogite

Ep-EC Epidote eclogite

HGR High-pressure granuliteAmp-EC Amphibole eclogite

Dry-EC Dry eclogite

Figure 5(a) Pressure-temperature (P-T ) diagram showing approximate P-T conditions of selected jadeitites from Guatemala, Cuba, Iran, theDominican Republic, and the Italian Alps (modied with permission after Tsujimori & Harlow 2012, Harlow et al. 2014). Also shownare reaction curves limiting jadeitite-bearing mineral equilibria, the Atg-out reaction, and Pg + Czo assemblage, as well as the modelledwet jadeitite solidus (this review) and P-T paths (model D80 of Syracuse et al. 2010) for slab surfaces in both warm (Nankai, southwestJapan) and cool (Tohoku, northeast Japan) subduction zones. The metamorphic facies boundaries are after Maruyama et al. (1996) andLiou et al. (2004); a boxed P-T space (250650C and 0.52.5 GPa) delineates the P-T pseudosection shown in panel b. (b) P-Tpseudosection calculated for the average SMM jadeitite composition (with the atomic ratios Si:Ti:Al:Fe:Mg:Ca:Na:K:O =51.06:0.06:23.56:0.54:1.05:1.31:22.13:0.29:151.69) in the NCFMASHT (NaO-CaO-FeO-MgO-Al2O3-SiO2-H2O-TiO2) system withexcess H2O; 0.1 mol C to stabilize CH4 was added to buffer oxygen fugacity. The color graduation level represents the modal volumeof jadeitic clinopyroxene; thin white lines with white-circled numbers are contour lines of this modal volume percentage. Contours ofamphibole composition (Na fraction in the A- and B-sites) are also shown as magenta and dark blue dotted lines.


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aqueous uid or the reaction Jd = Ne+Abwhen relatively dry. The resulting limits are0.6GPaat 200C or 0.7 GPa at 400C for the former reaction and 0.15 GPa at 200C or 0.65 GPaat 400C for the latter reaction. As uid inclusions and healed cavities and veins are common injadeitites, an aqueous uid is more than likely during formation. Fluid inclusion data reported byJohnson & Harlow (1999) for Guatemalan jadeitite (quartz-free, north of the Motagua fault zone)yield a lower T limit of 272C. These authors also calculated T based on the fractionation of 18Obetween albite andmuscovite, which yieldsT = 327C 50C for an albitite, and between jadeiteand albite, which yields T = 401C 50C; ve 18O temperatures for albite-muscovite pairsrange from 283C to 302C ( Johnson&Harlow 1999). Sorensen et al. (2006) measured 18O for ajadeite-albite pair from a Myanmar jadeitite, which yielded a best T estimate of 257C and arguedfor LT formation. Shi et al. (2003) constrained crystallization of an amphibole-bearing Myanmarjadeitite in a manner similar to Harlow (1994) with the addition of NaMgAl-amphibole reactionsand uid inclusion data to estimate T = 250C to 370C at P = 1 to 1.2 GPa. For Osayama,Japan, quartz-free jadeitite, homogenization T (Th) for two-phase aqueous uid inclusions ledShoji & Kobayashi (1988) to estimate a minimum jadeite crystallization T = 345C. Tsujimoriet al. (2005) used ThermoCalc software and the phase assemblage of Jd + Rt + Grs to estimateP > 1.2 GPa at 200300C.

For jadeitites manifesting Qz + Jd, P must exceed that dened by the Ab = Jd + Qz reaction.For jadeitite from Carrizal Grande, Guatemala, the combination of Qz + Jd and Lws indicateshigher P and lower T, consistent with the lawsonite-blueschist facies (SMM-cg in Figure 5a;Tsujimori et al. 2006a): P > 1.2 GPa and T = 300450C. Coexisting omphacite-jadeite in thesejadeitites suggests low T relative to the crest of the solvus of Carpenter (1981) at 600C or ofGreen et al. (2007) at 700C, with pairs estimated between 200C and >500C (Harlow et al.2011). For jadeitite from Tone, Japan, Czo coexists with Qz + Jd, so Shigeno et al. (2005) inter-preted crystallization atT > 400Cand P 1.3GPa. Jadeitite fromSierra del Convento representsa source yielding higher temperatures, 550C, from coexisting omphacite-jadeite compositions,at P of 1.5 GPa interpreted from the melange (Garca-Casco et al. 2009, Lazaro et al. 2009).The two different Ro San Juan complex jadeitites yielded different conditions. Quartz-bearingjadeitites from blueschist were evaluated through the presence of lawsonite and glaucophane,Si content in phengite, and a reasonable P-T-t path as forming at 350C to 550C and 1.4 to1.7 GPa (RSJC1 in Figure 5a), with the possibility of higher P. A similar evaluation for quartz-free jadeitites and the thermal structure of the subduction zone yielded 480C to 580C and1 to 1.3 GPa (RSJC2 in Figure 5a), roughly between the elds for the NMM and Sierra delConvento complex.

Another approach for determining P-T conditions is via the use of pseudosections, whichare based on whole-rock compositions and calculated limiting phase assemblages. Oberhansliet al. (2007) performed such an analysis on Iranian blue jadeitite (assemblage: Jd + Lws + Ktp)using the Theriak-Domino software (de Capitani & Petrakakis 2010) and obtained 400450Cat 1.61.7 GPa. A P-T pseudosection (equilibrium phase diagram) calculated for natural jadeititein the model system NCFMASHT (NaO-CaO-FeO-MgO-Al2O3-SiO2-H2O-TiO2) is shownin Figure 5b. The average composition (59.13 wt% SiO2, 0.09 wt% TiO2, 23.14 wt% Al2O3,0.75 wt% FeO, 0.02 wt% MnO, 0.82 wt% MgO, 1.42 wt% CaO, 13.22 wt% Na2O, 0.26 wt%K2O, 0.01 wt% P2O5, where FeO is the total amount of oxidized iron expressed as FeO) of24 Southern Motagua melange (SMM) jadeitites was used with excess H2O; MnO and P2O5were neglected. Calculation was performed using the Theriak-Domino software (de Capitani &Petrakakis 2010) with the internally consistent thermodynamic data set of Holland & Powell(1998); solution models suggested by Green et al. (2007), Dale et al. (2005), and Coggon &Holland (2002) were used for clinopyroxene, amphibole, and white mica, respectively. Modal


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Basalt: the mostcommon form of lavaon Earth, typicallywith 48 to 53 wt%SiO2

volume of jadeite and amphibole compositions were also calculated. In the P-T pseudosection, thestability elds of lawsonite, paragonite, Ca-Na amphibole (taramitic), two coexisting pyroxenes,and kyanite predict ve mineralogical types of jadeitite, namely lawsonite jadeitite, paragonitejadeitite, taramite jadeitite, two-pyroxene jadeitite, and kyanite jadeitite (Figure 5b). Moreover,the transformation of titanite-bearing to rutile-bearing mineral assemblages may further separaterutile-bearing jadeitite from rutile-free jadeitite. The modal volume of jadeitic pyroxenes reaches92 vol% in the paragonite jadeitite eld. Although the petrogenetic nature of jadeitite may castdoubt on the reliability of thermodynamic modellingespecially modelling with a xed bulk-rock composition, silica activity, etc.the chemographic relations in P-T space are still helpfulfor understanding the natural parageneses of jadeitites. For example, previous P-T estimates forlawsonite-bearing jadeitites with a trace amount of quartz and/or glaucophane from the SMMand taramite-bearing, lawsonite-free jadeitites from the NMM t P-T ranges of the inferredmineralogical types of jadeitite. It is also important that the pumpellyite stability eld lying at thelower-T side of the epidote stability eld is consistent with natural observations in Guatemala,whereas the stability eld of epidote-group minerals is highly controlled by the oxidation statesof iron and manganesei.e., oxygen fugacity. Our P-T pseudosection predicts kyanite-bearingjadeitite at P > 2.4GPa and600C that has not yet been reported. In theMonvisometaophiolite,R-type jadeitite with a plagiogranite protolith was estimated to have formed in the kyanite jadeititeeld (Figure 5a,b). However, the absence of kyanite in Monviso jadeitite is likely due to a lessaluminous bulk-rock composition.

The calculated wet solidus of an SMM jadeitite composition is shown in Figure 5a. Solutionmodels that Nagel et al. (2012) used to obtain the wet solidus of normal mid-ocean ridge basalt(N-MORB) and tholeiite (a subtype of basalt) were applied for our calculation. Themodeling sug-gests that initial partial melting of jadeitite occurs at >670700C and 1.21.7 GPa (higher thanthe temperature of antigorite breakdown) and that the temperature along a steady-state subduc-tion interface does not exceed the wet jadeitite solidus. Although the mantle wedge where P-typejadeitite forms is warmer than the underlying slab surface, jadeitite does not melt throughoutthe underow of jadeitite-bearing mantle wedge slices and melanges in steady-state subductionzones. In fact, xenoliths of jadeitite (eclogite containing up to 93 vol% jadeitic pyroxene) andmetasomatic omphacitite (Watson & Morton 1969, Schulze et al. 2014) that have no partial melt-ing, together with coesite-bearing lawsonite eclogite and antigorite serpentinite, were transportedfrom sinking of the Farallon plate by Oligocene kimberlitic plume upwelling. In the case of a non-steady-state scenario such as spreading-ridge subduction and hotter asthenospheric ow into themantle wedge, however, preexisting jadeitite remaining at the base of the mantle wedges may meltdue to warming of the geotherm.

3.3. How Jadeitite Forms

All of the contexts in which jadeitite is found are associated with rocks in the subduction channelor with the serpentinite formed by antigorite serpentinization of peridotite, presumably from theoverlyingmantle wedge (Figure 6). Several aspects of the latterandmost commonoccurrenceare important. For a hydrous uid to form a vein in peridotite or serpentinite, brittle fracture isrequired (Figure 7). Many arguments are made that cold, brittle, decoupled noses of the man-tle wedge in subduction zones are decoupled because they are brittle and are limited to depthsshallower than the decoupling depth of 75 15 km (Wada et al. 2008). However, evaluations ofwhether the ultramacs along the subduction channel boundary should deform by brittle deforma-tion aremixed (seeHirth&Guillot 2013). The conditions reported for all jadeitite, withmaximumP < 2.5 GPa and T < 600C and more generally P < 2.0 GPa and T < 500C, are reasonable for


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O C E A N I C C RU S T

A S T H E N O S P H E R E

Serpentinizedforearc mantle

wedge

Serpentinizedforearc mantle

wedge

A S T H E N O S P H E R E

M A G M AT I C A R C C R U S T100C

300

300

300

500

700

900

1,100900

700

500

300

100C

1,100

1,300C

1,300

1,300

C1,100 9

00700

L I T H O S P H E R IC

M A N T L E

L I T H O S P H E R I CM A N T L E

Jadeititedeposits

10 km

10 km

Forearcbasement

ExhumingHP rocksHydrouseclogite

Dryeclogite

500

HP serpentinitemlange

Volcanicfront

Accretionaryprism Trench

Eclogite-faciesmetamorphism

Blueschist-faciesmetamorphism

Figure 6Cross section showing a Phanerozoic Pacic-type subduction zone where jadeitite forms (modied after Stern et al. 2013, Tsujimori &Ernst 2014). Lithological variations and thermal structures are based on numerical modelling by Gerya (2011). Temperature contours(dashed white lines) are in degrees Celsius. Inferred occurrences of jadeitite in the cross section are denoted by green circles. P-typejadeitite forms in fractures in serpentinizing mantle wedge peridotite. Abbreviation: HP, high-pressure.

21 3

P E R I D O T I T E

P E R I D O T I T E

1

Fracture

aa bb

Jadeitite

Jadeitite

Cr-richCr-rich

Cr-richCr-rich

Newjadeitite

Serpentinite

Serpentinite

Serpentinite

Serpentinite

Fracture

1

Jadeitite

Figure 7Diagram of a model for jadeitite formation in veins in peridotite. (a) A boudinaged, less-serpentinized peridotite with hydrofractureswhere jadeite precipitation occurs (P-type jadeitite). This model is based on gure 3 from Nicolas & Jackson (1982) (boudinagedpyroxenite layer with syntectonic gabbroic veins). 1 is the maximum principal stress direction. (b) Stepwise uid inltration along thefracture/fault to form multigeneration P-type jadeitite (after Harlow & Sorensen 2005). As in Figure 4, the width of these veins andblocks can vary from about 1.5 to 50 m.


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the P-T interpretations along the boundary of the mantle wedge nose and the subduction channelin representative systems (e.g., Peacock 2001, Deschamps et al. 2013). The presence of antigoriterather than lizardite in the associated serpentinites further constrains temperatures to be above300C (Evans 2004) unless talc is present, for which T > 200C. Alternatively, hydrous uidentering peridotite without serpentinization requires only T = 430C at 0.7 GPa, where jadeiteis stable relative to analcime (Figure 5a). Our own observations of antigorite veins in antigoriteblocks from jadeitite-bearing melanges and the macroscopic dikes noted above argue that thereis brittle deformation and vein formation in the mantle wedge above the subduction channel.In support, Nicolas & Jackson (1982) have described gabbroic dikes/veins cutting a boudinagedpyroxenite layer within mylonitized peridotite from New Caledonia; the gabbroic dikes were in-jected into the extension plane related to the deformation. In themantle wedge and the subductionchannel, through a similar mechanism, it would be highly possible that rigid, less-serpentinizedperidotite portions are boudinaged within plastic, highly serpentinized peridotite or serpentiniteby their ductile deformation (Figure 7a). Considering the extensive heterogeneous distributionof serpentinization in most jadeitite-bearing melanges as well as on-land analogs of forearc man-tle sections, the heterogeneity of serpentinization and stress/strain in ultramac rocks above thesubducting slab would be an essential trigger for the formation of fractures where P-type jadeititescan form.

Another factor in forming veins is the hydrofracturing that is needed to drive the vein uidinto the host rock and is clearly expected in the context of uid along a fault boundary, suchas along the subduction channelmantle wedge boundary. Such events, as recorded by jadeititesworldwide, appear to be highly repetitive within jadeitites. Abundant growth bands, seen both incathodoluminescence and in backscattered electron imaging or X-ray mapping with the scanningelectron microscope, document fractures that have been inlled by later jadeite (see Figure 3).Brittle deformation, probably in the form of hydrofracture, apparently allows uid access tojadeitite masses. Some jadeitites show evidence for grain-boundary uid percolation, seen in anew generation of jadeite that decorates an aggregate of grains with different compositions. Otherspecimens contain shear zones that evidently comminuted grains by orders of magnitude. In a fewrocks, jadeite grains show partially resorbed cores of one composition, surrounded by growth-zoned, idioblastic jadeite. Jadeitites obviously testify to a dynamic formation environment withinhost serpentinite. Moreover, they suggest that the jadeitite veins appear to focus fracturing withinserpentinite, thus permitting the growth bands to be internal to the deformed solid jadeitite, inmany cases with cavity llings along apparent fractures, rather than external overgrowths on veins.

Jadeitite formation by uid entering fractures in the serpentinizing mantle wedge has severaldistinct consequences. If the ultramac is incompletely serpentinized, it will act like a sponge forthe H2O and silica from the uid during continued serpentinite formation. This results from thefollowing idealized reaction (simplied and ignoring the difference between lizardite and antigoritestoichiometry):

6Mg2SiO4 + 2SiO2(aqueous) + 2H2O = 4Mg3Si2O5(OH)4, (1)which avoids formation of brucite (not reported from serpentinites associated with jadeitite). Thissponge effect for H2O should assist in crystallization in veins by inducing supersaturation of theremaining uid. Additionally, many ultramac-hosted jadeitites (e.g., Myanmar, the NMM) arequartz free, which may well be the result of the reduced silica activity (Harlow 1994, Harlowet al. 2014). Another indication that this active serpentinization is involved in jadeitite vein crys-tallization is the presence of late-stage Ca enrichment in and around jadeitite bodies, particularlythe late omphacitites. Clinopyroxene is one of the last phases to break down in peridotite dur-ing serpentinization, so its release into the hydrous uid will be an indication of serpentinization


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reaction progress. Similarly, the breakdown of chromite in ultramacs is a late-stage process,which is recorded by Cr-richer (emerald-green) jadeite via late-stage veining and tectonic admix-ing. Finally, this evolution is consistent with the observation that nearby serpentinite hosts ofjadeitites contain few, if any, relict peridotite minerals (e.g., Coleman 1961, Harlow 1994).

Thus, a model for jadeitite crystallization in fractures in mantle wedge peridotite envisionsstepwise uid inltration along the fracture or fault, with progressive addition of jadeite to jadeitite(Figure 7b). As a conduit for uid into peridotite, serpentinization should zone outward from thelarge fracture by a mixture of grain boundarydriven and expansion-driven fracture, probablysimilarly to the case for peridotite carbonation as discussed by Kelemen et al. (2011). However,major fracturing apparently focuses along the vein and through the brittle jadeitite. Subduction-driven deformation leads to pinching and swelling, as with tension gashes, and rotation thatproduces blocks as well as veins. How this process relates to the formation of an active subductionchannel melange is unclear, but data on the timing in relation to exhumation are now beingassessed, as discussed below.

The interpretation of the formation of jadeitite as a metasomatic replacement of a protolith hasevolved over the years. The igneous albite granite dike interpretation for the Tawmaw,Myanmar,deposit invoked gain of Na2O and loss of SiO2 without addressing the issue of pressure (e.g.,Bleeck 1908, Chhibber 1934). Dobretsov & Ponomareva (1965) argued for a similar process withleucogabbros and granitoids included in the serpentinite from the Polar Urals and Itmurundy,Kazakhstan. A lack of any unmetasomatized bodies for these and other cases led to an interpretationof wholesale metasomatism of blocks in melanges for the above locations and for Guatemala (daSilva 1967, 1970; McBirney et al. 1967; Bosc 1971). Generally, the lack of pseudomorphism, therelics of protolith minerals, and the rhythmically zoned jadeite grains in the jadeitites from theselocales have eaten away at the metasomatism arguments.

More recent descriptions of jadeitites from the western Italian Alps and the Nishisonogi com-plex, Japan, have better established metasomatic (R-type) jadeitite. Compagnoni & Rolfo (2003)and Compagnoni et al. (2012) have identied relics of igneous pyroxene in the cores of jadeitegrains in a jadeitite block from Punta Rasciassa, Monviso metaophiolite, in support of the meta-somatic replacement of metagabbro. In addition, stringers of rutile running through the samplesuggest boudinage of a mac protolith. Shigeno et al. (2012) observed quartz inclusions in jadeitegrains in jadeitite from Tone and Mie in the Nishisonogi complex, for which micromodal analysisis consistent with a local replacement of albite. Nonetheless, both sets of authors observe jadeiteovergrowths on these cores and in these jadeitites, indicating that they have a P-type crystallizationcomponent.

As the context of R-type jadeitite requires a mac to felsic protolith, either rocks from the sub-duction channel or igneous intrusions into ultramac must be involved. For the Tone jadeitite,an acid igneous rockprobably a plagiogranite (trondhjemite-tonalite)was believed to be theprotolith, on the basis of the inclusions in and the trace element patterns of relict igneous zircons,which also recorded the igneous age (see below; Mori et al. 2011). In a somewhat different con-text, Garca-Casco et al. (2009) interpreted the jadeitite of the Sierra del Convento melange asbeing primary jadeitite but resulting from the complete metasomatic replacement or dissolutionand precipitation of components from peraluminous tonalitic-trondhjemitic rocks in the upperplate, which in turn formed from partial ux melting of mac amphibolites from the subductionchannel that had been accreted to the sole of the upper plate. This might be the context of theTone felsic protolith as well. Alternatively, tonalite-trondhjemite-diorite suites are the lithologiesgrouped as plagiogranites in oceanic settings formed near spreading centers and preserved bothin classic obducted (or accreted) ophiolites (see Dilek & Furnes 2014) and in suprasubductionsettings from melting of young amphibolites of a subducted spreading center (hot subduction and


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shallow melting; Shervais 2001, 2008); however, how the latter might get into a HP/LT envi-ronment is an interesting question. In their study of jadeitite and jadeite-quartz rock from theMonviso metaophiolite, which is composed of subducted crust in a near-slow-spreading-ridgesetting, Compagnoni et al. (2012) demonstrated a close concordance between the whole-rockcomposition signatures of metaplagiogranite, jadeitite, and jadeite-quartz rock, as well as a simi-larity in the zircons in the three rock types. They concluded that the jadeitite was derived from aplagiogranite protolith.

Finally, there are those jadeitites included in blueschists (PB- or RB-type) and other metaba-sites, such as in the Ro San Juan complex melange. These rocks, which can be either true jadeititescontaining little other than jadeite or jadeite-bearing rocks containing considerable quartz, law-sonite, etc., have recently been recognized as a distinct type of jadeitite. Although they are part ofserpentinite-bearing melanges, they are probably derived from uids permeating the metabasites;it is not yet clear whether serpentinites play a signicant role in their formation. There appear tobe many similar occurrences of small jadeite veins in metabasites [e.g., Escambray massif, Cuba(Maresch et al. 2012); Ward Creek, Franciscan complex, California (Tsujimori & Harlow 2012)],where similar processes are at work but the veins do not become magnied by some repetitiveprocess to yield blocks that would be considered separate rocks (or jade).

4. FLUIDS, SOLUTES, SOLUBILITIES, AND SOURCES

Given the strong evidence for crystallization of jadeitites fromor evenmetasomaticmodicationof a protolith byauid, determining that uids characteristics, source, and solute load is criticallyimportant.

4.1. Fluid Compositions

Various lines of evidence reveal the composition of the uid. Fluid inclusion salinities and O/Hisotopic systematics in jadeitites from the NMM have been interpreted to indicate the predomi-nance of a seawater-like uid that is entrained during subduction rather than being the product ofdehydration of deep metamorphic minerals ( Johnson & Harlow 1999). Sisson et al. (2006) haveexamined uid inclusions further, nding two-phase aqueous inclusions with salinity ranges from2 to 8 wt% NaCl equivalent and Th from 170C to 300C. In the SMM, inclusions in jadeite arepredominantly two-phase aqueous with salinity ranges from 0 to 3 wt% NaCl equivalent and Thfrom 115C to 200C, but there are some one-phase inclusions and rare CH4-H2O inclusions.None of the two-phase inclusions are sufciently dense to have been preserved from the growthconditions, implying either erroneous estimates of growth conditions or some stretching sinceentrapment; the authors favor the latter. Moreover, the range in salinities suggests different uidsin the NMM versus the SMM: saltier and less salty than seawater, respectively. Fluid inclusionsin Hpakan, Myanmar, jadeite also show H2O-rich and CH4-rich uid compositions, between3.0 and 8.5 wt% NaCl equivalent and with Th from 315C to 378C (Shi et al. 2005). The Thvalues appear high, particularly in comparison with Guatemalan samples that otherwise have asimilar interpreted P-T-X origin. Possibly, the Myanmar jadeite inclusions were all reset duringexhumation. However, the authors did not present enough data about the sizes of uid inclusionsto determine whether this is the case. Isotopic measurements by Shi et al. (2005) yielded 13C(CH4) from30.1 to25.5 and D (H2O) from56.3 to48.8; these ndings were in-terpreted as indicating abiogenic methane produced by thermal maturation of subducted organiccarbon and either a metamorphic uid contribution to the D/H systematics or later diffusionalexchange with the enclosing serpentinite. The authors also argued for immiscible liquids for the


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two different kinds of inclusions but did not provide much evidence. This latter point contrastswith the observation of heavier H in the Guatemalan rocks; however, the measurements are ondifferent phases in the rocks. By comparison, both primary and secondary uid inclusions in eclog-ite and garnet amphibolite samples from the Franciscan complex and Catalina schist, California,and the Samana Peninsula, Dominican Republic, preserve seawater-like salinities (Sorensen &Barton 1987, Giaramita & Sorensen 1994). Meng et al. (2011), in their research on jadeitite fromSyum-Keu, have reported both H2O-rich and CH4-rich uid inclusions, which they describe asone-phase but are clearly imaged as two-phase; no interpretation was made about these inclusionsother than their consistency with prior research on jadeitite. For Osayama quartz-free jadeitite,Th for two-phase aqueous uid inclusions led Shoji & Kobayashi (1988) to estimate a minimumjadeite crystallization T of 345C.

Beyond the above interpretations, we have observed hydrous and some gas uid inclusionsin the thin sections of jadeitites we have observed, which represent many of the 19 occurrences;however, we have not done detailed studies beyond those cited above.

4.2. Source of Solutes Inferred From Jadeitite Samples

For a P-type jadeitite, if the model is correct, the bulk composition must reect the geochemicaltransport of species dissolved in the uid from its source and pathways and deposited by crys-tallization in its host. So, what are the characteristics of jadeite in jadeitite as well as whole-rockcompositions beyond the simple dominance of a jadeite-like composition?

In an electron and ion (secondary ionmass spectrometry)microprobe study guided by cathodo-luminescence images of zoning in jadeite grains in jadeitite from Myanmar, Guatemala, Japan,Kazakhstan, andCalifornia, Sorensen et al. (2006) reported consistent trends of increasingCa,Mg,and Cr in traversing from early red and blue cathodoluminescence zones toward later green zones,typically with an increase in elements such as Li, Rb, Sr, Ti, Hf, Zr, and light rare earth elements(LREEs). Here we have replotted the data in a spidergram to show the entire pattern together(Figure 8). Individual samples show large variations in the concentrations of these trace elementsas well as changes in 18O that can only be explained by multiple sources of uid. Sorensen et al.(2006) suggest that the oxygen signature of the jadeite grains is mirrored by the uid from whichthey grew, with three major sources reected in the data: seaoor altered by seawater at low T,seaoor altered at higher T, and an igneous or mantle source. In a laser ablation inductivelycoupled plasma mass spectrometry study of jadeite and omphacite in P-type jadeitite from theItoigawa-Omi district, Japan, Morishita et al. (2007) interpreted elevated large ion lithophile ele-ment (LILE) patterns, higher LREEs than HREEs, and positive anomalies of high eld strengthelements (HFSEs) relative to primitive mantle values; they suggested these ndings were due toslab-derived uids relatively rich in LILEs and HFSEs from interaction with subducted crustand serpentinized peridotites. Among elements measured in jadeite, only Li, Ni, Zr, Hf, and Nbexceed N-MORB values (Sun & McDonough 1989); when omphacite is considered, Sr and Crare included in this list as well. This difference may point to the importance of crystal chemistry,given how trace elements enter crystal structures (e.g., Sr into Ca-rich omphacite, Li into Na-richjadeite and omphacite), and of timing, as omphacite is late in jadeitites in general and is likelyliberated late during serpentinization of peridotite.

By considering whole-rock analysis, some of the minor phases that are important in jadeititesare made obvious, although some signatures are consistent with the data above. A conspicuousfeature of jadeitites from Myanmar and Guatemala is minor late-stage barium phases: cymrite(BaAl2Si2O8H2O), celsian, banalsite, and hyalophane, as well as primary barian phengitic mus-covite (Guatemala only). Some barian phases are found in jadeitite from California, Dominican


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Li Cs Rb K Ba Pb Sr Ni La Ce Pr Nd SmElement

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Primitive mantleOcean island basaltGlobal subducting sedimentAntilles terrigenous sedimentsMn-bearing lavender jadeiteAll other jadeite

Guatemala

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b Myanmar

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Eu Gd Y Dy Er Lu Sc Th U Cr Zr Hf Ti Nb Ta


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Republic, and Iran. Itoigawa-Omi jadeitite contains some celsian and Ba-rich K-spar but isknown for its variety of strontiumminerals such as itoigawaite [SrAl2Si2O7(OH)2H2O], rengeite(Sr4ZrTiSi4O22), and matsubaraite [Sr4Ti5(Si2O7)2O8]. Sr is enriched only in some calcic phases,such as lawsonite and zoisite, among Guatemalan jadeitites and is not very conspicuous in otherjadeitites (see Harlow et al. 2011, 2014). These elements become conspicuous in the whole-rockdata.

A limited amount of whole-rock analysis is available among the deposits that have been studied.Starting with jadeitite interpreted as fundamentally of P-type, the best data for samples from theJade Mine Tract in Myanmar (Shi et al. 2008) show the enrichment of Ba but not Sr, as suspectedfrom mineralogy, but also high Pb; somewhat high U (>Th); low Rb, K, and Ti; and a depletedconcave rare earth element (REE) pattern with a positive Eu anomaly, as shown in a eld-strength-organized spider diagram normalized toN-MORB (Figure 9) (Sun&McDonough 1995). Simonset al. (2010) presented data on a single sample from the SMM,which has now been augmented by acomprehensive suite of jadeitites from various locales in both the SMM and NMM (G.E. Harlow,K.E. Flores &H.R.Marschall, manuscript in preparation). These data show some similarities withtheMyanmar samples, with highCs, Ba, andU, but otherwise showmore variability in the range ofvalues while sharing the same general pattern shape within each general source area, such as attermore depleted REE patterns from the NMM versus asymmetric concave REE patterns straddlingN-MORB values from the SMM [the pattern for sample MVE02-8-5 of Simons et al. (2010)shows the pronounced Eu anomaly not observed in a newer analysis, which suggests incompletepowder digestion in the former plus some Eu contamination, as no other samples show thesecharacteristics; nonetheless, the data are included here]. Syros and Tinos jadeitites are categorizedas a mixture of P-type and R-type formation, so interpreting the jadeitite compositions (Brocker& Enders 2001) is problematic; nonetheless, the plotted data (Figure 9) are quite consistent withBa>KSr; enrichedU (Th), Zr (>Hf ),Nb, andTa; and at, somewhat enrichedREEpatterns.Data from other P-type jadeitite sources [e.g., Itoigawa-Omi (Miyajima 1999) and Sorkhan, Iran(Oberhansli et al. 2007)] are incomplete and thus are not plotted or considered. Among theseP-type jadeitites, in spite of the differences, there are similarities in enriched Ba (Pb or Sr)among the LILEs, U (Th) compared with the REEs, and maybe Zr and Hf as well. Presumably,these features represent some combination of solute source, namely the subduction channel, andrelative solubility in some unknown but large ux of hydrous uid escaping from the channel.

The obvious candidates for the source of solutes in the uids that precipitate P-type jadeititeare the components of the subducted oceanic crust, namely altered oceanic (basaltic) crust and thesediments overlying it. Simons et al. (2010) examined these possibilities in their study ofGuatemalajadeitite and its constituents, with a focus on Li content and isotopic signature. They found thatthe Li concentration in jadeite (90 g/g; somewhat less in jadeitite) was signicantly greaterthan in N-MORB (36 g/g), island arc basalt (510 g/g), and altered oceanic crust (414 g/g)and generally heavier (+2 to +7.5 7Li) compared with either jadeitite or eclogite (5 to+5 7Li), such that a dehydration process with Rayleigh fractionation would not likely producethe observed signature in jadeitites. Sediments, in contrast, have both greater Li concentration and

Figure 8Normal mid-ocean ridge basalt (N-MORB)-normalized trace element pattern for jadeite from jadeitites. (a) Guatemala (Sorensen et al.2006, Harlow & Shi 2011). (b) Myanmar (Sorensen et al. 2006, Harlow & Shi 2011). (c) Itoigawa-Omi, Japan (Sorensen et al. 2006,Morishita et al. 2007, Harlow & Shi 2011). Normalized value and reference values are from Sun & McDonough (1989), McDonough& Sun (1995), and Plank & Langmuir (1998). Except for Sorensen et al.s (2006) secondary ion mass spectrometry data, all data werecollected by laser ablation inductively coupled plasma mass spectrometry.


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Primitive mantleOcean island basaltGlobal subducting sedimentAntilles terrigenous sediments

NMM jadeititeSMM jadeititeMyanmar jadeititeItoigawa-Omi jadeitite

Syros/Tinos jadeititeSyros omphacititeNishisonogi jadeitite

Monviso jadeititeMonviso quartz-jadeitite rockMonviso plagiogranite

Nishisonogi omphacitite

Cs Rb K Ba Pb Sr Ni La Ce Pr Nd SmElement

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Eu Gd Y Dy Er Lu Sc Th U Cr Zr Hf Nb Ta


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lower 7Li compared with altered oceanic crust. Global subducted sediment (Plank & Langmuir1998) or its Li-evaluated counterpart global Li mass-weighted sediment (43 g/g Li, 7Li =3.01; Chan et al. 2006), and particularly sediments with a continental source afnity, such asthe Lesser Antilles (69.6 g/g Li), were selected for modeling a dehydration path to yield a uidfrom which jadeitite could be crystallized. Moreover, sediments are a potential source of elevatedLILEs and Th, U, Zr, Hf, Nb, and Ta, as can be seen in the whole-rock composition plots inFigure 9, to which global subducted sediment and Antillean terrigenous sediment values havebeen added. Li is not included in these plots because data on Li are available only from Myanmarjadeitites (a range of 26 to 35 g/g for six samples, and one sample at 5.8 g/g); however, Figure 8,with just jadeite values, shows that Li is relatively high in jadeite in many, but not all, jadeitites.

The spider plots in Figure 9 use eld strength for elemental order to better gauge the roleof crystal and uid chemistry rather than igneous compatibility, and they manifest some featuresworth discussion.With the LILEs on the left, differentiated igneous rocks and clay-rich sedimentsgenerally show strong enrichments; however, jadeitites without mica are decient in K comparedwith N-MORB, but less so than for Rb and particularly Cs in most cases where reported. Baand Sr are discussed above with respect to mineralogy, but Pb is in the plots among the alkalineearth metals. Ba is a good signature of sediment, being a constituent of both pelagic and terres-trial detrital sediments (as shown in global subducted sediment data); it is conspicuously high inGuatemala, Myanmar, and Nishisonogi jadeitites and less so in Cyclades jadeitites and is nowherereported as low. Sr is only modestly high in Itoigawa jadeitites and moderately low in Guatemala,Cyclades, Myanmar, and Sorkhan jadeitites, whereas Pb can be transitional between Sr and Ba(Guatemala, most Myanmar samples) or higher (Tone, Nishisonogi, two Myanmar samples). Niand Cr are added as monitors of interactions with ultramac, such as from release into the uidupon completion of some serpentinization reactions; the values are very low where reported, sug-gesting little feedback during jadeitite crystallization. Th, U, Zr, and Hf are higher eld strengthelements that are generally considered less mobile. Jadeitites clearly show sympathetic variationwithin the pairs (Th and U; Zr and Hf ) and varied concentrations, but following the pattern ofeither sediment or more evolved igneous rocks. These four elements are generally higher in thejadeitites from Cyclades and the SMM and lower in those from Myanmar and the NMM. Thehighest eld strength pair is Nb and Ta, which are less well constrained but follow the trends ofthe previous four elements where measured, similar to sediment and ocean island basalt.

The REE patterns show considerable variation among jadeitites and make for an interestingcomparison with sediment and oceanic igneous rocks. A characteristic of both sediments andevolved basaltic rocks (e.g., ocean island basalt) is an LREE-enriched pattern, decreasing withincreasing atomic number (Figure 9). The same is true for global subducted sediment and theAntillean terrigenous sediment used in our comparison. In contrast, plagiogranite and trond-hjemite, whether of suprasubduction zone or near-ridge origin, have generally at and slightly

Figure 9Normal mid-ocean ridge basalt (N-MORB)-normalized whole-rock minor trace element composition spidergrams for jadeitites.(a) Jadeitites from the Northern Motagua melange (NMM) and Southern Motagua melange (SMM) of Guatemala (Simons et al. 2010;G.E. Harlow, K.E. Flores & H.R. Marschall, manuscript in preparation); from Myanmar (Shi et al. 2008); and from Itoigawa-Omi,Japan (Miyajima 1999). (b) Jadeitites and omphacitites from Syros and Tinos, Greece (Brocker & Enders 2001), and from Nishisonogi,Japan (Shigeno et al. 2012). (c) Jadeitites and associated quartz-jadeite rock and plagiogranite from Monviso, Italy (Compagnoni et al.2012). Normalized value and reference values are from Sun & McDonough (1989), McDonough & Sun (1995), and Plank & Langmuir(1998). The order of the elements is based on eld strength (ionic radius/ionic charge) for sixfold coordination rather than on meltincompatibility to better reect crystal/solution chemistry. Radii are from Shannon (1976).


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enriched patterns (more like N-MORB) with a minimal to small negative Eu anomaly. On a rst-order basis, unless there is a multimineral dependence on REE patterns that would affect patternsof solubilized REEs, the protolith pattern for solute (or just the protolith) probably represents thatin solution. Thus, the REEpattern in jadeitite should resemble that in the solubilized source, offsetby the capacity of REEs to substitute for Ca in jadeite, omphacite, or another Ca-bearing phase injadeitite. The REE patterns in jadeitite that are LREE enriched (e.g., the SMM, Nishisonogi, andperhapsMyanmar)may owe that enrichment to sediment or ocean island basalt, whereas the atterpatterns (e.g., Cyclades and the NMM) may owe their patterns to (N-)MORB or plagiogranite.Itoigawa data are limited but appear to show both trends. Myanmar REE data are concave with apositive Eu anomaly.

The other half of understanding the REEs in jadeitite and their possible relationship to sourceor uid composition is the mineral(s) that host(s) these elements. If allanite is the dominant host,the rock pattern will most likely be LREE enriched, whereas if monazite is dominant, the patternmay be atter and convex. Jadeite itself plays a role in REE uptake to the extent that pure jadeititedoes not offer a large crystallographic site for the REEs, but increased Ca content provides thesite expansion in the average structure to accommodate more REEs; this is particularly evidentin more calcic jadeitites (e.g., SMM jadeitite, Cyclades omphacitites; Brocker & Enders 2001).Guatemala jadeitites typically contain more REE-rich clinozoisite and allanite than monazite,which may explain the pattern shape. Nishisonogi jadeitites are reported to contain allanite butnot monazite. These are both consistent with REE patterns. The Myanmar jadeitites have rareallanite but very depleted REE patterns, so connecting the shape to a mineral or solute sourceremains difcult.

In conclusion, the enrichments in the LILEs Ba, Pb, and perhaps Sr, as well as in Li, areconsistent with crystallization from uids derived from a sediment-rich source and probably con-trolled in the jadeitite by compatibility in jadeite (for Li) and in minor phases such as the Ba- orSr-silicates, epidote-group minerals, or mica (for the LILEs). Without saturation of K-mica, Kis usually depleted. Enrichments in more immobile elements such as Th, U, Zr, Hf, Nb, andTa appear to correlate with an enriched source, such as sediment, but how this transport occursmust relate to solubilities at HP/LT conditions and uid ux, addressed below. This is not to sug-gest that the main bolus of solutesNa, Al, and Sidoes not come from altered oceanic crust, asSimons et al. (2010) have suggested, because clearly its dehydration must be involved in producingthe hydrous uid indicated in the jadeitite formation process.

4.3. Protolith for R-Type Jadeitite Samples

R-type jadeitites have been interpreted as desilicied plagiogranite or some other felsic protolithentrained in a melange

annual review earth jadeite and tectonic

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