U, Th Enrichment in Cesium Bearing Aplitic Pegmatite of Belamu (North) Area, Purulia District, West Bengal with Special Reference to Monazite Group of Minerals

Celsium bearing aplitic pegmatites ot Chhotanagpur Gneissic complcx Purulia district. West Bengal show enrichment in U and Th through at least one phase of lanthanide actinide rich hydrothermal activity. Monazite group of minerals with Th and REE are hosted by the aplitic pegmatites with varying texture and composition. Monazite(Ce) occurs as inclusions within quartz and feldspar with evolutionary trcnd from huttonitic monazite at core to monazite (Ce) at rim Ce/Sm ratio varies from 8 11 to 25 67 representing a wider evolutionary trend of the melt from which monazite crystallized. Principal component analysis shows different subsitution phenomenon in monazite. Chemical variations indicate the huttonitic monazite to be a primitive component which was transformed to monazite (Ce) by interaction with LREE P-rich fluid.