OCCURRENCE OF MONAZITE IN SOME ALLUVIAL SOILS OF NORTH-BIHAR

Monazite, a thorium-bearing mineral, has been identified in the heavy mineral fractions of the fine sands from the alluvial soil profiles at Barpalia and Gyaspur of Siwan district in north Bihar. The amount of monazite varied from 14.29 to 15.40% and 6.25 to 9.38% of the heavy mi nerals in the fine sands of Barpalia and Gyaspur, respectively. Monazi te could have been derived from the granite pegmatite and gneissic met amorphic rocks in association with feldspar, zircon and apatite from t he Himalayan orogan. The amount of Th-232 present in monazite original ly ranges from a few wt% ThO2 to 10-12% 1. Even in the east coast of I ndia, monazite contains 9.05% ThO2.