Petrology and Geochemistry of Mafic–Ultramafic Rocks from Taka Area, Western Bastar Craton, Central India: An Implication for Their Genesis and Mineralization Potential

The serpentinite and associated talc-tremolite-chlorite ± chromite occurs as enclaves and small lensoidal bodies within Amgaon granite gneiss around Taka village and adjoining areas of western Bastar craton, Central India. In the present study, we report petrological, mineralogical and geochemical data for these rocks. These data help to interpret the petrogenesis, composition of parental melt and their tectonic setting. These rocks are entirely serpentinized, showing well-developed mesh, hourglass and zoned textures containing bastite pseudomorphs. Serpentinite and talc-tremolite schist consist of chromite in the form of fine dissemination, cumulates and at places as bands. Cr-spinel is equigranular, euhedral to subhedral in shape and exhibits primary cumulus to intercumulus texture. Cr-spinel contains high Cr# and low TiO2 content, which indicates arc tectonic setting. Two different normalized REE patterns, namely a flat pattern with low HREE and fractionated LREE depleted pattern are observed. The IPGE (Ir, Ru) enrichment relative to PPGE (Pd, Pt, Rh) and the relatively low Pd/Ir values suggest that their parental melts were produced by melting of a moderately depleted peridotite similar to the ones described for other IPGE rich chromitites originated in back arc basins in supra-subduction zones setting. Parental magma compositions of this high Cr-spinel suggest the reaction between boninitic melts and depleted peridotites for Taka serpentinite that got generated by partial melting of mantle in the supra-subduction zone setting.