Mantle heterogeneity and crust-mantle interaction in the Singhbhum craton, India: New evidence from 3340 Ma komatiites

Abstract The Singhbhum Craton in eastern India preserves the records of Paleoarchean - Mesoarchean oceanic crust dominated by ultramafic-mafic extrusive rocks (greenstones), and sialic rafts composed of tonalite-trondhjemite-granodiorite, together with younger granitoids constituting the composite Singhbhum granite batholith. The greenstone sequences, intruded by younger granitoids are entrained as synformal keels in the batholith. The lower greenstone sequence of eastern Iron Ore Group (IOG) is composed of peridotitic komatiite, and komatiitic basalt with minor chert and BIF, whereas the upper sequence has tholeiite to tholeiitic andesite. Here we report results from first direct dating of the Karanjharan spinifex-textured komatiite from the lower part of Badampahar greenstone sequence of IOG. LA-ICPMS U-Pb analysis of zircon grains in the komatiites yielded consistent weighted mean 207Pb/206Pb age of 3340 Ma, with closely similar Hf depleted mantle age (TDM) between 3357 Ma and 3432 Ma. The high MgO (25–35%), and low Al2O3/TiO2 (