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Article: REE and PGE geochemical constraints on the formation of dunites in the Luobusa ophiolite, Southern Tibet

TitleREE and PGE geochemical constraints on the formation of dunites in the Luobusa ophiolite, Southern Tibet
Authors
KeywordsHydrous melt
Mantle
Melt-rock interaction
Ophiolite
PGE
REE
Tibet
Issue Date2005
PublisherOxford University Press. The Journal's web site is located at http://petrology.oxfordjournals.org/
Citation
Journal Of Petrology, 2005, v. 46 n. 3, p. 615-639 How to Cite?
AbstractThe Luobusa ophiolite, Southern Tibet, lies in the Indus-Yarlung Zangbo suture zone that separates Eurasia to the north from the Indian continent to the south. The ophiolite contains a well-preserved mantle sequence consisting of harzburgite, clino-pyroxene (cpx)-bearing harzburgite and dunite. The harzburgite contains abundant pods of chromitite, most of which have dunite envelopes, and the cpx-bearing harzburgites host numerous dunite dykes. Dunite also exists as a massive unit similar to those of the mantle-crust transition zones in other ophiolites. All of the dunites in the ophiolite have a similar mineralogv, comprising mainly olivine with minor orthopyroxene and chromite and traces of clinopyroxene. Thg also display similar chemical compositions, including U-shaped chondrite-normalized REE patterns. Mantle-normalized PGE patterns show variable negative Pt anomalies. Detailed analysis of a chromite-bearing dunite dyke, which grades into the host cpx-bearing harzburgite, indicates that LREE and Ir decrease, whereas HREE, Pd and Pt increase away from the dunite. These features are consistent with formation of the dunite dykes by interaction of MORB peridotites with boninitic melts from which the chromitites were formed. Because the transition-zone dunites are mineralogically and chemically identical to those formed by such melt rock reaction, we infer that they are of similar origin. The Luobusa ultramafic rocks originally formed as MORB-source upper mantle, which was subsequently trapped as part of a mantle wedge above a subduction zone. Hydrous melts generated under the influence of the subducted slab at depth migrated upward and reacted with the cpx-bearing harzburgites to form the dunite dykes. The modified melts ponded in small pockets higher in the section, where they produced podiform chromitites with dunite envelopes. At the top of the mantle section, pervasive reaction between melts and harzburgite produced the transition-zone dunites. © The Author 2004. Published by Oxford University Press. All rights reserved.
Persistent Identifierhttp://hdl.handle.net/10722/72949
ISSN
2015 Impact Factor: 3.768
2015 SCImago Journal Rankings: 2.992
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorZhou, MFen_HK
dc.contributor.authorRobinson, PTen_HK
dc.contributor.authorMalpas, Jen_HK
dc.contributor.authorEdwards, SJen_HK
dc.contributor.authorQi, Len_HK
dc.date.accessioned2010-09-06T06:46:37Z-
dc.date.available2010-09-06T06:46:37Z-
dc.date.issued2005en_HK
dc.identifier.citationJournal Of Petrology, 2005, v. 46 n. 3, p. 615-639en_HK
dc.identifier.issn0022-3530en_HK
dc.identifier.urihttp://hdl.handle.net/10722/72949-
dc.description.abstractThe Luobusa ophiolite, Southern Tibet, lies in the Indus-Yarlung Zangbo suture zone that separates Eurasia to the north from the Indian continent to the south. The ophiolite contains a well-preserved mantle sequence consisting of harzburgite, clino-pyroxene (cpx)-bearing harzburgite and dunite. The harzburgite contains abundant pods of chromitite, most of which have dunite envelopes, and the cpx-bearing harzburgites host numerous dunite dykes. Dunite also exists as a massive unit similar to those of the mantle-crust transition zones in other ophiolites. All of the dunites in the ophiolite have a similar mineralogv, comprising mainly olivine with minor orthopyroxene and chromite and traces of clinopyroxene. Thg also display similar chemical compositions, including U-shaped chondrite-normalized REE patterns. Mantle-normalized PGE patterns show variable negative Pt anomalies. Detailed analysis of a chromite-bearing dunite dyke, which grades into the host cpx-bearing harzburgite, indicates that LREE and Ir decrease, whereas HREE, Pd and Pt increase away from the dunite. These features are consistent with formation of the dunite dykes by interaction of MORB peridotites with boninitic melts from which the chromitites were formed. Because the transition-zone dunites are mineralogically and chemically identical to those formed by such melt rock reaction, we infer that they are of similar origin. The Luobusa ultramafic rocks originally formed as MORB-source upper mantle, which was subsequently trapped as part of a mantle wedge above a subduction zone. Hydrous melts generated under the influence of the subducted slab at depth migrated upward and reacted with the cpx-bearing harzburgites to form the dunite dykes. The modified melts ponded in small pockets higher in the section, where they produced podiform chromitites with dunite envelopes. At the top of the mantle section, pervasive reaction between melts and harzburgite produced the transition-zone dunites. © The Author 2004. Published by Oxford University Press. All rights reserved.en_HK
dc.languageengen_HK
dc.publisherOxford University Press. The Journal's web site is located at http://petrology.oxfordjournals.org/en_HK
dc.relation.ispartofJournal of Petrologyen_HK
dc.rightsJournal of Petrology. Copyright © Oxford University Press.en_HK
dc.subjectHydrous melten_HK
dc.subjectMantleen_HK
dc.subjectMelt-rock interactionen_HK
dc.subjectOphioliteen_HK
dc.subjectPGEen_HK
dc.subjectREEen_HK
dc.subjectTibeten_HK
dc.titleREE and PGE geochemical constraints on the formation of dunites in the Luobusa ophiolite, Southern Tibeten_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0022-3530&volume=46&spage=615&epage=639&date=2005&atitle=REE+and+PGE+geochemical+constraints+on+the+formation+of+dunites+in+the+Luobusa+ophiolite,+Southern+Tibeten_HK
dc.identifier.emailZhou, MF: mfzhou@hkucc.hku.hken_HK
dc.identifier.emailMalpas, J: jgmalpas@hku.hken_HK
dc.identifier.authorityZhou, MF=rp00844en_HK
dc.identifier.authorityMalpas, J=rp00059en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1093/petrology/egh091en_HK
dc.identifier.scopuseid_2-s2.0-14744292154en_HK
dc.identifier.hkuros123391en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-14744292154&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume46en_HK
dc.identifier.issue3en_HK
dc.identifier.spage615en_HK
dc.identifier.epage639en_HK
dc.identifier.isiWOS:000227133100008-
dc.publisher.placeUnited Kingdomen_HK
dc.identifier.scopusauthoridZhou, MF=7403506005en_HK
dc.identifier.scopusauthoridRobinson, PT=7403720506en_HK
dc.identifier.scopusauthoridMalpas, J=7006136845en_HK
dc.identifier.scopusauthoridEdwards, SJ=7401520329en_HK
dc.identifier.scopusauthoridQi, L=7202149924en_HK
dc.identifier.citeulike99246-

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