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Article: Enrichment of PGE through interaction of evolved boninitic magmas with early formed cumulates in a gabbro-breccia zone of the Mesoarchean Nuasahi massif (eastern India)

TitleEnrichment of PGE through interaction of evolved boninitic magmas with early formed cumulates in a gabbro-breccia zone of the Mesoarchean Nuasahi massif (eastern India)
Authors
KeywordsBoninite
Breccia
Chromite
Gabbro
India
Metasomatism
Nuasahi
Pge
Issue Date2010
PublisherSpringer Verlag. The Journal's web site is located at http://link.springer.de/link/service/journals/00126/index.htm
Citation
Mineralium Deposita, 2010, v. 45 n. 1, p. 69-91 How to Cite?
AbstractThe Mesoarchean Nuasahi chromite deposits of the Singhbhum Craton in eastern India consist of a lower chromite-bearing ultramafic unit and an upper magnetite-bearing gabbroic unit. The ultramafic unit is a ~5 km long and ~400 m wide linear belt trending NNW-SSE with a general north-easterly dip. The chromitite ore bodies are hosted in the dunite that is flanked by the orthopyroxenite. The rocks of the ultramafic unit including the chromitite crystallized from a primitive boninitic magma, whereas the gabbro unit formed from an evolved boninitic magma. A shear zone (10-75 m wide) is present at the upper contact of the ultramafic unit. This shear zone consists of a breccia comprising millimeter- to meter-sized fragments of chromitite and serpentinized rocks of the ultramafic unit enclosed in a pegmatitic and hybridized gabbroic matrix. The shear zone was formed late synkinematically with respect to the main gabbroic intrusion and intruded by a hydrous mafic magma comagmatic with the evolved boninitic magma that formed the gabbro unit. Both sulfide-free and sulfide-bearing zones with platinum group element (PGE) enrichment are present in the breccia zone. The PGE mineralogy in sulfide-rich assemblages is dominated by minerals containing Pd, Pt, Sb, Bi, Te, S, and/or As. Samples from the gabbro unit and the breccia zone have total PGE concentrations ranging from 3 to 116 ppb and 258 to 24,100 ppb, respectively. The sulfide-rich assemblages of the breccia zone are Pd-rich and have Pd/Ir ratios of 13-1,750 and Pd/Pt ratios of 1-73. The PGE-enriched sulfide-bearing assemblages of the breccia zone are characterized by (1) extensive development of secondary hydrous minerals in the altered parts of fragments and in the matrix of the breccia, (2) coarsening of grain size in the altered parts of the chromitite fragments, and (3) extensive alteration of primary chromite to more Fe-rich chromite with inclusions of chlorite, rutile, ilmenite, magnetite, chalcopyrite, and PGE-bearing chalcogenides. Unaltered parts of the massive chromitite fragments from the breccia zone show PGE ratios (Pd/Ir = 2.5) similar to massive chromitite (Pd/Ir = 0.4-6.6) of the ultramafic unit. The Ir-group PGE (IPGE: Ir, Os, Ru) of the sulfide-rich breccia assemblages were contributed from the ultramafic-chromitite breccia. Samples of the gabbro unit have fractionated primitive mantle-normalized patterns, IPGE depletion (Pd/Ir = 24-1,227) and Ni-depletion due to early removal of olivine and chromite from the primitive boninitic magma that formed the ultramafic unit. Samples of the gabbro and the breccia zone have negative Nb, Th, Zr, and Hf anomalies, indicating derivation from a depleted mantle source. The Cu/Pd ratios of the PGE-mineralized samples of the breccia zone (2.0 × 103-3.2 × 103) are lower than mantle (6.2 × 103) suggesting that the parental boninitic magma (Archean high-Mg lava: Cu/Pd ratio ~1.3 × 103; komatiite: Cu/Pd ratio ~8 × 103) was sulfur-undersaturated. Samples of the ultramafic unit, gabbro and the mineralized breccia zone, have a narrow range of incompatible trace element ratios indicating a cogenetic relationship. The ultramafic rocks and the gabbros have relatively constant subchondritic Nb/Ta ratios (ultramafic rocks: Nb/Ta = 4.1-8.8; gabbro unit: Nb/Ta = 11.5-13.2), whereas samples of the breccia zone are characterized by highly variable Nb/Ta ratios (Nb/Ta = 2.5-16.6) and show evidence of metasomatism. The enrichment of light rare earth element and mobile incompatible elements in the mineralized samples provides supporting evidence for metasomatism. The interaction of the ultramafic fragments with the evolved fluid-rich mafic magma was key to the formation of the PGE mineralization in the Nuasahi massif. © Springer-Verlag 2009.
Persistent Identifierhttp://hdl.handle.net/10722/151301
ISSN
2015 Impact Factor: 3.467
2015 SCImago Journal Rankings: 1.677
ISI Accession Number ID
Funding AgencyGrant Number
Department of Geological Sciences, Indiana University
Chinese 973
Funding Information:

We are grateful to Eric Essene, Jens Anderson, and an anonymous reviewer for the comments to improve the science of this article. Eric Essene and Jens Anderson are acknowledged for editing of the initial draft. We are grateful to Peter Lightfoot for editorial handling and his effort to improve this article. Bernd Lehmann, editor-in-chief of the journal, is acknowledged for comments on the article. Support rendered by mining authorities such as IMFA, FACOR, and OMC during field works are acknowledged. SEM observations were conducted in the laboratory of Department of Geological Sciences, Indiana University, Bloomington. Chusi Li, Ed Ripley, Ed Mathez, and Minik Rosing are acknowledged for support to SKM. MFZ is supported by a Chinese 973 matching fund from the HKU.

References

 

DC FieldValueLanguage
dc.contributor.authorMondal, SKen_US
dc.contributor.authorZhou, MFen_US
dc.date.accessioned2012-06-26T06:20:16Z-
dc.date.available2012-06-26T06:20:16Z-
dc.date.issued2010en_US
dc.identifier.citationMineralium Deposita, 2010, v. 45 n. 1, p. 69-91en_US
dc.identifier.issn0026-4598en_US
dc.identifier.urihttp://hdl.handle.net/10722/151301-
dc.description.abstractThe Mesoarchean Nuasahi chromite deposits of the Singhbhum Craton in eastern India consist of a lower chromite-bearing ultramafic unit and an upper magnetite-bearing gabbroic unit. The ultramafic unit is a ~5 km long and ~400 m wide linear belt trending NNW-SSE with a general north-easterly dip. The chromitite ore bodies are hosted in the dunite that is flanked by the orthopyroxenite. The rocks of the ultramafic unit including the chromitite crystallized from a primitive boninitic magma, whereas the gabbro unit formed from an evolved boninitic magma. A shear zone (10-75 m wide) is present at the upper contact of the ultramafic unit. This shear zone consists of a breccia comprising millimeter- to meter-sized fragments of chromitite and serpentinized rocks of the ultramafic unit enclosed in a pegmatitic and hybridized gabbroic matrix. The shear zone was formed late synkinematically with respect to the main gabbroic intrusion and intruded by a hydrous mafic magma comagmatic with the evolved boninitic magma that formed the gabbro unit. Both sulfide-free and sulfide-bearing zones with platinum group element (PGE) enrichment are present in the breccia zone. The PGE mineralogy in sulfide-rich assemblages is dominated by minerals containing Pd, Pt, Sb, Bi, Te, S, and/or As. Samples from the gabbro unit and the breccia zone have total PGE concentrations ranging from 3 to 116 ppb and 258 to 24,100 ppb, respectively. The sulfide-rich assemblages of the breccia zone are Pd-rich and have Pd/Ir ratios of 13-1,750 and Pd/Pt ratios of 1-73. The PGE-enriched sulfide-bearing assemblages of the breccia zone are characterized by (1) extensive development of secondary hydrous minerals in the altered parts of fragments and in the matrix of the breccia, (2) coarsening of grain size in the altered parts of the chromitite fragments, and (3) extensive alteration of primary chromite to more Fe-rich chromite with inclusions of chlorite, rutile, ilmenite, magnetite, chalcopyrite, and PGE-bearing chalcogenides. Unaltered parts of the massive chromitite fragments from the breccia zone show PGE ratios (Pd/Ir = 2.5) similar to massive chromitite (Pd/Ir = 0.4-6.6) of the ultramafic unit. The Ir-group PGE (IPGE: Ir, Os, Ru) of the sulfide-rich breccia assemblages were contributed from the ultramafic-chromitite breccia. Samples of the gabbro unit have fractionated primitive mantle-normalized patterns, IPGE depletion (Pd/Ir = 24-1,227) and Ni-depletion due to early removal of olivine and chromite from the primitive boninitic magma that formed the ultramafic unit. Samples of the gabbro and the breccia zone have negative Nb, Th, Zr, and Hf anomalies, indicating derivation from a depleted mantle source. The Cu/Pd ratios of the PGE-mineralized samples of the breccia zone (2.0 × 103-3.2 × 103) are lower than mantle (6.2 × 103) suggesting that the parental boninitic magma (Archean high-Mg lava: Cu/Pd ratio ~1.3 × 103; komatiite: Cu/Pd ratio ~8 × 103) was sulfur-undersaturated. Samples of the ultramafic unit, gabbro and the mineralized breccia zone, have a narrow range of incompatible trace element ratios indicating a cogenetic relationship. The ultramafic rocks and the gabbros have relatively constant subchondritic Nb/Ta ratios (ultramafic rocks: Nb/Ta = 4.1-8.8; gabbro unit: Nb/Ta = 11.5-13.2), whereas samples of the breccia zone are characterized by highly variable Nb/Ta ratios (Nb/Ta = 2.5-16.6) and show evidence of metasomatism. The enrichment of light rare earth element and mobile incompatible elements in the mineralized samples provides supporting evidence for metasomatism. The interaction of the ultramafic fragments with the evolved fluid-rich mafic magma was key to the formation of the PGE mineralization in the Nuasahi massif. © Springer-Verlag 2009.en_US
dc.languageengen_US
dc.publisherSpringer Verlag. The Journal's web site is located at http://link.springer.de/link/service/journals/00126/index.htmen_US
dc.relation.ispartofMineralium Depositaen_US
dc.subjectBoniniteen_US
dc.subjectBrecciaen_US
dc.subjectChromiteen_US
dc.subjectGabbroen_US
dc.subjectIndiaen_US
dc.subjectMetasomatismen_US
dc.subjectNuasahien_US
dc.subjectPgeen_US
dc.titleEnrichment of PGE through interaction of evolved boninitic magmas with early formed cumulates in a gabbro-breccia zone of the Mesoarchean Nuasahi massif (eastern India)en_US
dc.typeArticleen_US
dc.identifier.emailZhou, MF:mfzhou@hkucc.hku.hken_US
dc.identifier.authorityZhou, MF=rp00844en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1007/s00126-009-0264-0en_US
dc.identifier.scopuseid_2-s2.0-77749326544en_US
dc.identifier.hkuros177761-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-77749326544&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume45en_US
dc.identifier.issue1en_US
dc.identifier.spage69en_US
dc.identifier.epage91en_US
dc.identifier.isiWOS:000273403300006-
dc.publisher.placeGermanyen_US
dc.identifier.scopusauthoridMondal, SK=7102824988en_US
dc.identifier.scopusauthoridZhou, MF=7403506005en_US
dc.identifier.citeulike5955857-

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