REE geochemistry of uranium-bearing columbite-tantalites and multiple oxide phases from proterozoic rare metal pegmatites of Pandikimal and adjoining areas, Jharsuguda district, Orissa

摘要

Rare earth element (REE) geochemistry of uranium bearing columbite-tantalite and multiple Nb-Ta oxide phases from the Pandikimal-Jangapara pegmatites, Jharsuguda district, Orissa have been studied and evaluated. Columbite-tantalite from these areas contain low Sigma REE (100-1000 ppm) with LREE/HREECN 0.5 and minor amounts of uranium (0.3-0.6%U3O8). Multiple oxide phases (yttrotantalite, samarskite, microlite and fergusonite) contain elevated amounts of U (10-11% U3O8) and REE (1.9-2.8%) with HREE>LREE. Plot of Sigma REE vs chondrite-normalised LREE/HREE shows positive correlation in 'U'rich multiple oxides compared to those from columbite-tantalites which tend to show a negative correlation. The LREE/HREE ratio is 0.24 with negative Eu anomaly (Eu/Eu* = 0.1) indicating evolved nature of these pegmatites.