RARE-EARTH ELEMENT GEOCHEMISTRY OF SELECTED MAFIC-ULTRAMAFIC UNITS FROM SINGHBHUM CRATON - IMPLICATIONS TO SOURCE HETEROGENEITY

Modelling of REE data indicates that while mafic rocks of Dhanjori Gro up are partial melting products of a spinel Iherzolite source, Dalma u ltrabasics are the residue after the melt-extraction from an original garnet Iherzolite rock. Ultramafics of Newer dolerite dykes indicate e ither derivation by mantle meta somatism or effect of post magmatic se rpentinisation. REE data in conjunction with the available geochronolo gical data suggest that significant mantle heterogeneity existed over relatively smaller distances (similar to 100 km) even during Proterozo ic and that the mantle evolved in a non-uniform manner with distinct l ocalised processes.