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Article: Controls on platinum-group elemental distributions of podiform chromitites: A case study of high-Cr and high-Al chromitites from Chinese orogenic belts

TitleControls on platinum-group elemental distributions of podiform chromitites: A case study of high-Cr and high-Al chromitites from Chinese orogenic belts
Authors
Issue Date1998
PublisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/gca
Citation
Geochimica Et Cosmochimica Acta, 1998, v. 62 n. 4, p. 677-688 How to Cite?
AbstractA study of podiform chromite deposits from the Asiatic Orogenic Belt and the Qilian-Qiangling-Kunlun-Himalaya Tectonic Domain provides new insights into the geochemistry of the PGEs in podiform chromite deposits and the genesis of the deposits themselves. The bulk of deposits, which occur in mantle peridotites of ophiolites, have typical ophiolitic PGE patterns that are depleted in Pt and Pd relative to the average upper mantle and have negatively sloping distributions on mantle-normalized diagrams. Type I (high-Cr) chromitites have higher Os, Ir, Ru, and Rh contents than Type II (high-Al) chromitites, although both have similar Pd and Pt. Most of the Type I and II chromite deposits have lower Pd and Pt contents than the upper mantle peridotites in which they occur. Podiform chromitites are essentially products of melt/rock interaction in the upper mantle; their Cr and PGEs were contributed by not only the invading magmas but also by the upper mantle host; the chromite deposits are, in part, metasomatic replacement bodies. The Type I (high-Cr) chromitite PGE patterns were produced by interaction between S-undersaturated boninitic magmas and depleted harzburgites, whereas the Type II (high-Al) chromitite PGE patterns were formed by interaction between initially S-saturated tholeiitic magmas and depleted harzburgites. The low to very low Pd and Pt contents of both Type I and Type II chromitites require that the mantle assemblage in which the chromite deposits were formed had lost their sulfides, and hence Pd and Pt, prior to formation of the chromite deposits; in addition, no or little Pd and Pt were deposited by the invading magma which either remained S-undersaturated (boninite) or became (MORB) S-undersaturated due to interaction with the S-depleted harzburgitic mantle. It is suggested that the very low Ir, Os, and Ru contents of boninites in general might be due to loss of Ir during the formation of podiform chromitites. It is suggested that podiform chromitites with Type IPGE patterns were formed in an island arc environment, whereas those with Type IIPGE patterns were formed in a back-arc setting. Copyright © 1998 Elsevier Science Ltd.
Persistent Identifierhttp://hdl.handle.net/10722/150999
ISSN
2015 Impact Factor: 4.315
2015 SCImago Journal Rankings: 3.016
References

 

DC FieldValueLanguage
dc.contributor.authorZhou, MFen_US
dc.contributor.authorSun, Men_US
dc.contributor.authorKeays, RRen_US
dc.contributor.authorKerrich, RWen_US
dc.date.accessioned2012-06-26T06:15:41Z-
dc.date.available2012-06-26T06:15:41Z-
dc.date.issued1998en_US
dc.identifier.citationGeochimica Et Cosmochimica Acta, 1998, v. 62 n. 4, p. 677-688en_US
dc.identifier.issn0016-7037en_US
dc.identifier.urihttp://hdl.handle.net/10722/150999-
dc.description.abstractA study of podiform chromite deposits from the Asiatic Orogenic Belt and the Qilian-Qiangling-Kunlun-Himalaya Tectonic Domain provides new insights into the geochemistry of the PGEs in podiform chromite deposits and the genesis of the deposits themselves. The bulk of deposits, which occur in mantle peridotites of ophiolites, have typical ophiolitic PGE patterns that are depleted in Pt and Pd relative to the average upper mantle and have negatively sloping distributions on mantle-normalized diagrams. Type I (high-Cr) chromitites have higher Os, Ir, Ru, and Rh contents than Type II (high-Al) chromitites, although both have similar Pd and Pt. Most of the Type I and II chromite deposits have lower Pd and Pt contents than the upper mantle peridotites in which they occur. Podiform chromitites are essentially products of melt/rock interaction in the upper mantle; their Cr and PGEs were contributed by not only the invading magmas but also by the upper mantle host; the chromite deposits are, in part, metasomatic replacement bodies. The Type I (high-Cr) chromitite PGE patterns were produced by interaction between S-undersaturated boninitic magmas and depleted harzburgites, whereas the Type II (high-Al) chromitite PGE patterns were formed by interaction between initially S-saturated tholeiitic magmas and depleted harzburgites. The low to very low Pd and Pt contents of both Type I and Type II chromitites require that the mantle assemblage in which the chromite deposits were formed had lost their sulfides, and hence Pd and Pt, prior to formation of the chromite deposits; in addition, no or little Pd and Pt were deposited by the invading magma which either remained S-undersaturated (boninite) or became (MORB) S-undersaturated due to interaction with the S-depleted harzburgitic mantle. It is suggested that the very low Ir, Os, and Ru contents of boninites in general might be due to loss of Ir during the formation of podiform chromitites. It is suggested that podiform chromitites with Type IPGE patterns were formed in an island arc environment, whereas those with Type IIPGE patterns were formed in a back-arc setting. Copyright © 1998 Elsevier Science Ltd.en_US
dc.languageengen_US
dc.publisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/gcaen_US
dc.relation.ispartofGeochimica et Cosmochimica Actaen_US
dc.titleControls on platinum-group elemental distributions of podiform chromitites: A case study of high-Cr and high-Al chromitites from Chinese orogenic beltsen_US
dc.typeArticleen_US
dc.identifier.emailZhou, MF:mfzhou@hkucc.hku.hken_US
dc.identifier.emailSun, M:minsun@hku.hken_US
dc.identifier.authorityZhou, MF=rp00844en_US
dc.identifier.authoritySun, M=rp00780en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.scopuseid_2-s2.0-0031851321en_US
dc.identifier.hkuros33973-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0031851321&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume62en_US
dc.identifier.issue4en_US
dc.identifier.spage677en_US
dc.identifier.epage688en_US
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridZhou, MF=7403506005en_US
dc.identifier.scopusauthoridSun, M=25932315800en_US
dc.identifier.scopusauthoridKeays, RR=7005122208en_US
dc.identifier.scopusauthoridKerrich, RW=7005649319en_US

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