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dc.contributor.authorGhose, N.C.
dc.contributor.authorSaha, A.
dc.date.accessioned2019-12-31
dc.date.accessioned2020-02-04T09:38:24Z
dc.date.available2019-07-01
dc.date.available2020-02-04T09:38:24Z
dc.date.issued2019
dc.identifier.citationGeological Journal, vol.54(4); 2019; 1927-1949
dc.identifier.urihttps://doi.org/10.1002/gj.3271
dc.identifier.urihttp://drs.nio.org/drs/handle/2264/8258
dc.description.abstractThe Chakradharpur granite gneiss (CGG) represents an uplifted Archaean basement within the North Singhbhum Orogen (NSO) of Singhbhum-Orissa Craton in the eastern Indian shield and shares a Mesoarchaean 3.12�Ga age equivalent to the emplacement of Singhbhum granite (SBG) phase III. The CGG hosts numerous enclaves of tonalitic gneisses, metamorphosed ultramafic and mafic volcanics, metagabbros, metasediments, and conglomerates that collectively represent vestiges of an older greenstone belt preserved within it. The mineralogical composition of the ultramafic volcanic enclaves of CGG has been overprinted by greenschist facies metamorphism presenting a talc-tremolite-phlogopite-actinolite assemblage with prominent development of crenulation cleavage, pressure solutions and relict spinifex texture. These are characterised by restricted low SiO2 (39.7-46.8�wt.%) at consistently high MgO (20.7-28�wt.%) contents, and geochemically classified as: (a) subalkaline (Na2O�+�K2O�<�2) komatiite and meimechite and (b) an alkaline (Na2O�+�K2O�>�2) type picrobasalt-foidite-basanite assemblage. Depleted LILE and LREE chemistry, Al2O3/TiO2 versus (Gd/Yb)N and HFSE abundances suggest that the studied Al-undepleted Munro-type komatiite and meimechite were derived by high degree (30%-50%), shallow level (<90�km) partial melting of a hot, anhydrous mantle plume carrying depleted components. It is suggested that the komatiite-meimechite melts were deflected by an Archaean cratonic keel and erupted through thinned continental lithosphere at a rifted cratonic margin. Geochemical evidence of crustal contamination preserved in these komatiites are equated with minor input from reworking of older continental materials and interaction between plume-derived asthenospheric melts and metasomatized subcontinental lithospheric mantle (SCLM). Zr/Hf, Zr/Sm, Nb/Ta, Zr/Nb, and Nb/Th ratios for the picrobasalt, high Mg basalt, foidite and basanite rocks corroborate their generation through variable degrees of partial melting of a heterogeneous lithospheric mantle source carrying depleted plume-derived melts and enriched components from metasomatized lithosphere. Mantle processes involved assimilation of metasomatic components of SCLM by ascending melts of plume incubating at the base of lithosphere ensued by melt generation at different mantle depths extending from garnet to spinel peridotite domains. Therefore, the geochemical signatures of ultramafic enclaves in CGG invoke distinct magmatic �
dc.languageen
dc.relation.isreferencedbySCI
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dc.titleVestiges of older greenstone in Mesoarchaean Chakradharpur granite gneiss, Singhbhum Craton, India: Implications for plume-lithosphere interaction at rifted cratonic margin
dc.typeJournal Article


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