The REE-bearing minerals of intercratonic extensional zone in Chhotonagpur continental plate of Eastern Indian Shield

Abstract

The REE-bearing minerals occurring in the baryte-bearing pegmatites of Nawahatu (23°26′N, 86°04′E), Purulia District, belong to the intercratonic extensional zone in the Chhotonagpur continental plate of Eastern India. Mineralogical and microchemical investigations of REE-bearing minerals reveal their extreme inhomogeneity showing associations of both high temperature minerals like those of euxenite group and low temperature minerals like aeschynite. While the presence of Ba together with traces of Au, Cr, Ni, FeMg-silicates and even P are evidences for the probable fractional crystallisation of the rare earth elements from the upper mantle, the Al and Si-bearing REE minerals are indicative of crustal origin. The presence of U 6+ together with Cl − and OH − shows metasomatic influence subsequent to hydrothermal activity. It is predicted that fractional crystallisation from the lower crust and partly from the upper mantle as well as the subsequent granite-pegmatite intrusion with metasomatic alteration have led to the formation of economically important REE-bearing minerals.