Uranium mineralisation in the migmatites around Rasgandha-Belangi, Surguja district, Madhya Pradesh, India

Uranium mineralisation located near Rasgandha waterfall near village Belangi, Surguja district, Madhya Pradesh is mainly confined to lenticular bodies (10 m to 40 m X 2 m to 25 m) of highly altered migmatite basificates and to a lesser extent (2 m to 3 m X 10 m) in the less altered migmatite mobilizates, both intimately associated. The Chhotanagpur gneisses of this area are peraluminous (A/CNK 1.35), potassic (6.47% K2O), and anomalously rich in uranium (x-bar = 36 ppm; n = 69) and low in thorium (x-bar = 11 ppm; n =69) with an average Th/U = 0.31. These rocks are highly fractionated and evolved which got migmatised during the Satpura orogeny. Enrichment of uranium in the reducing phases of basificates had taken place along with formation of magnetite, marcasite, and pyrite. Later effects of anatexis, shearing, and concomitant hydrothermal activity resulted in further enrichment of uranium. Uraninite, masuyite, zircon, allanite, and monazite constitute the radioactive minerals. Uranium contents in basificates [0.03% to 1.00% U3O8 (β/γ)] are more compared to mobilizates [0.01% to 0.08% U3O8 (β/γ)]. Ferromagnesian elements (Fe, Mg, Ni, and V) and volatiles (CO2, F-, CI-, and OH-) seem to have fixed uranium in basificates. (author). 16 refs., 10 figs., 4 tabs