Uranium mineralization in some typical igneous-metamorphic environments of India

The paper presents the characteristics of uranium mineralization in three distinctive geological environments, two of which are related to magmatic and post-magmatic processes of enrichment and one to metamorphic processes aiding uranium mineralization. Granitoids emplaced into migmatitic complexes host uranium mineralization along shear zones in the Surguja-Palamau belt of Madhya Pradesh and Bihar. At Jajawal in the Surguja District of Madhya Pradesh sheared migmatite and associated amphibolites are the main hosts; in addition there is a minor uranium mineralization in the associated feldspathic biotite schist. Uraninite and coffinite occur as veins and fracture fillings in intimate association with autunite, fluorite, pyrite and minor chalcopyrite and pyrrhotite. In the granitoids of the Binda-Nagnaha area of the Palamau District, Bihar, uraninite is the chief uranium mineral. Microgranites and rhyolitic dykes emplaced into the acid-basic volcanic sequences of the Proterozoic (Dongargarh Supergroup) of Madhya Pradesh have intrinsically higher contents of uranium, and are further enriched along shear zones, resulting in the formation of uraninite with some U-Ti complexes. In the Sikkim Himalayas uranium mineralization is encountered in the phosphatic phyllites of the marine Daling-Buxa sequences deposited originally under euxinic conditions. The tectonics of the region are characterized by the presence of large thrust sheets, some of which slide along the lithostratigraphic contact zones. The exploration strategy in identifying deposits of uranium in the igneous and metamorphic environments calls for an integrated approach of interpretation of Landsat images with airborne gamma ray spectrometric data followed up largely by radiometric surveys, geological mapping and exploratory drilling. 12 refs, 7 figs, 4 tabs