Fluids in High- To Ultrahigh-temperature Metamorphism Along Collisional

8/10/2019 Fluids in High- To Ultrahigh-temperature Metamorphism Along Collisional

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A B S T R A C T

Fluids in high- to ultrahigh-tempmetamorphism along collisio

sutures: Record from uid inclu

Fluidos en alto a metamorfsmo de utemperatura a lo largo de las suturcolisin: Registro de inclusiones


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Petrographic studies and microthermometricinvestigations on uid inclusions associated withto ultrahigh-temperature metamorphic rocks in tmajor Precambrian suture ones on the globdemonstrate the dominant occurrence o C!-riuids"

!" !ST#$%& AS&C%A$& A '!TA'&RF%SS'& $R&CAS $! %(C"#S%&(!S $! A"TA A #"TRA A"T!'P!RAT#RA R!A"%)A$& !( "AS TR!S

PR%(C%PA"!S )&(!S $! S#T#RA $!"principales onas de sutura Prec,mbricos


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#hese rocks orm part o hot orogens developecollisional plate boundaries"

!SAS R&CAS F&R'A( PART! $! &T .RAB/ue se desarrollaron a lo largo de limites d

placas colisionales


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The sapphirine-/uart-bearing 'g0Al-rich roc1 from the PaCau2er3 Suture )one* a trace o the Cambrian $ondwana suturesouthern &ndia' preserves evidence or a prograde high-pressure esubse(uent peak ultrahigh-temperature metamorphism along a clpath' and contains abundant C!-rich inclusions in corundum' garsapphirine" )ost o the uid inclusions are either primar3 or seco

and preser2e lo4-densit3 C&+-rich uids 56789067;6< g=cm

#n rastro de la ona de sutura C,mbrico .ond4ana en el s%ndia* conser2a e2idencia de un e2ento progrado de alta prposterior metamorsmo pico ultra alta temperatura a lo laun camino hacia la derecha


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*imilar lo4-densit3 C&+-rich uid inclusions,"1./ g2cm/3 are also present in pelitic granulrom the 4impopo Comple5 o southern Africa' a(eoarchean granulite-facies orogen3 formedcontinent0continent collision


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&n contrast' the garnet0orthop6ro5ene granulite r#onagh &sland in the 7eoarchean 7apier Comple5 9ntarctica contains 2er3 high-densit3 primar3"!1 g2cm/3 and secondar3 +,"1;,0"


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===================>

#he calculated isochores or the uid inclusions rPalghat-Cauver6 *uture ?one and the 4impopo Co6ield signifcantl6 lower-pressure estimates than tpredicted rom peak metamorphic

conditions"

@e interpret this as a result of signicant densdecrease due to rapid decompression along a cloP0# traAector6


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&n contrast' the estimated isochores or primar6inclusions in garnet0

orthop6ro5ene granulites rom the 7apier Compleconsistent with the peak P0# conditions estimatedmineral phase e(uilibria or the #onagh &sland roc

suggesting that most o the uid inclusions in thedid not undergo an6 marked eBect o volume chadensit6 decrease


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#he contrasting uid densities among the localitinvestigated in this stud6 are probabl6 related tonature o the P0# traAector6 the #onagh &sland roa near-isochoric ehumation histor3 whereametamorphic orogens in the other two sutureswitnessed rapid decompression


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ur results suggest that whereas the compositions6n-metamorphic uids are preserved in all casesdensit6 reversal occurs within inclusions as a uncthe tectonic histor6 and e5humation st6le"


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%(TR&$#CT%&(#he P0#0t architecture and uid regimes o metam

orogens have received wide attention in evaluatinghistor6 o evolution o continents and supercontinehave also been central to some o the recent debatsurrounding the plate tectonic paradigm +e"g"' Drow!,, 8rnst' !,, )aru6ama et al"' !,, #irone a$angul6' !,, *antosh' !,, *antosh et al"' !,,1


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Chemical and ph3sical characteriation of thof uids

associated 4ith high-grade metamorphism hbeen one o the ocal

themes in petrological research' particularl6 inunderstanding

the stabilit3 of mineral assemblages* uid0rinteraction processes*

and degree of partial melting in lo4er crust

*antosh


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#he nature o uids associated with metamorphicprocesses has been inerred through a number otechni(ues including thermod6namic calculationsmineral assemblages' geochemical and isotopic sand investigation o uids trapped within inclusio

various minerals"


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9mong these' detailed investigation o the uidinclusions in

various metamorphic minerals provides directinormation on the

nature' composition' and densit6 o uids at variostages o the

metamorphic processes +e"g"' #ouret' 1.' !,,'


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Recent investigations on the characteri%ation o associated with high- to ultrahigh-temperaturemetamorphism' particularl6 along collisional sutu%ones' have provided critical inormation on P0# eand e5humation histor6 o hot orogens along colli

plate boundaries +e"g"' h6ama et al"' !,, *antal"' !,,' !,, #sunogae and *antosh' !,,3" Eonot man6 studies have attempted to compare theinclusion data rom ultrahigh-temperature rocks within Precambrian collision sutures in understand

nature and role o uids"


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&n this stud6' we s6nthesi%e inormation on the occurrence'composition' and densit6 o uid inclusions trapped in 2arious

granulite-facies minerals from ultrahigh-temperature m

roc1s in three collisional orogenic belts:(eoproterooic

Cambrian Palghat-Cau2er3 Suture )one+*outhern &ndia F

(eoarchean to 'esoproterooic "impopo Comple 5SoutFig7 Db?* and (eoarchean (apier Comple +8ast 9ntarctica

c3" #ogether with newl6 obtained data' we attempt a comparis

on the nature o the trapped uids rom these regions


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The Palghat- Cau2er3 Suture )one and the"impopo Comple are regarded as collisionsutures that record the histor3 of high-preand ultrahigh-temperature metamorphismvan Reenen et al"'!,, *antosh et al"' !,,1b3 ashould thus preserve uids associated with the

collisional event" the 7apier Comple5 is not well but is also regarded as a possiblecollisional oro


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ur results provide new evidence on the role o rich uids along collisional sutures as well asimplications on densit6 reversal as a probable uo the tectonic histor6"


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+7 Palghat-Cau2er3 Suture )Southern %ndia

#he southern granulite terrane in &ndia comprisescrustal

blocks which were welded together during the "A(!&PR&T!R&)&%C

T& !AR"E CA'BR%A(collisional orogen6 related

fnal

amalgamation o the $ondwana supercontinent +e*antosh

et al"' !,,1b3"


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#he Palghat-Cauver6 *uture ?one 5PCS)? is an !trending network o transpressional shears thathe boundar6 between the "ate (eoproterooic!arl3 Cambrian'adurai Bloc1 to the south aArchean $har4ar Craton to the north 5Fig7 D

+Chett6 and Dhaskar Rao' !,,; Collins et al"' !,,*antosh et al"' !,,;' !,,1b Clark et al"' !,,1a et al"' !,, *ato et al"' !, 7aganAane6ulu and*antosh' !,,3


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9vailable geochronological studies on the high-grmetamorphic rocks rom this region have confrm4idespread eGect o a ca" 8860 8>6 'a therme2ent related to the collisional amalgamation o $ondwana supercontinent +e"g"' *antosh et al"' !,

!,,;' !,,1b Collins et al"' !,,


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Previous petrological studies on this region documthe evidence or a prograde high-pressure 5P? eand subse(uent ultrahigh-temperature 5#T?metamorphism along a cloc14ise path +e"g"' *et al"' !,,; Collins et al"' !,,


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Fluid inclusion studies o metamorphic rocks 4ithPCS)

include those on 'g0Al-rich granulites +h6am!,,3 and

mac granulites +7ishimi6a et al"' !,, *antos

!,,3"

#he results rom these studies show the occurrenabundant

C&+-rich inclusions in 'g0Al-rich roc1s and

retrogressed eclogites


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'ost of the reported inclusions are secondar3in origin' probabl6 trapped during the post-pea1decompression

stage' and generall6 contain lo4-densit3 +,".10,"1

cm/3 C!" Eowever' primar6 and pseudosecondar6 h

+G",; g2cm/3 C&+-rich uid inclusions have beenmatri5

staurolite and plagioclase rom the )g09l-rich rocks +

et al"' !,,3


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Primar6 uid inclusions within garnet in the mafcgranulites rom HanAa )alai and *ittampundi withPC*? are

also high-densit3 C&+ +up to ". g2cm/ *antoal"' !,,3"

Eowever' recent geochronological studies suggessome o

these roc1s are relicts of an earlier high-gradmetamorphic e2ent

in the (eoarchean +e"g"' *ato et al"' in press *a


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#his is also consistent with the occurrence o e5trhigh-densit3

carbonic uid inclusions in an Archean charnrom the

*alem Dlock north o the PC*? +*antosh and #sun

!,,/ *antosh

et al"' !,,I3"


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&n order to evaluate the nature o uids associat4ith the

high-grade metamorphism 4ithin the PCS)' obtained new

petrographic and microthermometric data o uid

inclusions in a

sapphirine-bearing )g09l-rich rock rom Panangadcentral

part o the PC*?


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#he anal6%ed rock +sample )J1-!J3 contains

)g-rich staurolite inclusions in garnet and the staurolite

replaced b6 sapphirine K (uart% corona +7ishimi6a et al

#sunogae and *antosh' !,,3' suggesting a prograde EPmetamorphism

and subse(uent peak LE# metamorphism" #he rock is co porph6roblastic garnet in the matri5 o gedrite'

sapphirine' corundum' and spinel' with accessor6 stauro

rutile +Fig" !a3"

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Fluids in High- To Ultrahigh-temperature Metamorphism Along Collisional

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