Trace element composition of fluorite from the Chumathang pegmatite deposit, eastern Ladakh, India

Abstract

The fluorite deposit of the Chumathang area of south-eastern Ladakh, India, is hosted in pegmatite which cross-cuts the Paleogene Chumathang granite. The rare earth element and yttrium (REE-Y) and the trace element's composition of different colored (green, purple, and white) fluorite were investigated to understand its genesis. The green fluorite core is surrounded by purple fluorite, indicating that green fluorite crystallized earlier than the purple one. The white fluorite is mineralized with green fluorite, it does not exhibit any zoning like the other fluorite. The REE pattern of green and white fluorites is similar to those in the host pegmatite and associated Chumathang granite. ƩREE content in fluorite increases from green, white to purple. Fluorites in the study area are characterized by negative Ce suggesting partial reducing conditions during its formation. The Y/Y*, Ce/Ce*, and Eu/Eu* ratios show that fluorite records the compositional evolution of the hydrothermal solutions that transported the trace and REE from the host granite during the fluid–wall rocks interactions. The fluorite exhibits a positive Y anomaly which is suggestive of strong Y-Ho fractionation in the fluid system. Chumathang fluorite show significant degrees of differentiation between terbium (Tb) and lanthanum (La) in all the purple, green, and white colored fluorite. The Tb/La and Tb/Ca ratios of the fluorites confirm the role of pegmatitic melt and hydrothermal fluid in the genesis of Chumathang fluorite.