Geological, Mineralogical and Geochemical Study of the Aquamarine-Bearing Yamrang Pegmatite, Eastern Nepal with Implications for Exploration Targeting

The Yamrang Pegmatite in the Ikhabu Field, Eastern Nepal is Nepal’s primary source of aquamarine. This paper reports detailed mineralogy and whole rock granite pegmatite geochemistry, major trace element data for alkali feldspar muscovite order to classify aquamarine-bearing Pegmatite, elucidate beryl-saturation processes evaluate potential geochemical exploration tools beryl-pegmatites. Five internal mineralogical/textural zones were identified Pegmatite; zone 1 (saccharoidal albite); 2 (blocky perthitic microcline); 3 (muscovite–microcline–quartz); 4 (beryl-quartz), 5 (miarolitic cavities). Zones 1–4 represent magmatic stage, while formed during hydrothermal stage genesis. Spectacular aquamarines are recovered from miarolitic 5, beryl saturation found 3, 4, 5. Based on beryllium (Be) content, Be partition among co-existing minerals at > tourmaline quartz. In contrast, sequence albite content rock-forming decreases margin core, could have played a significant role enrichment marginal zone. High temperature, low degree fractionation, dominance Be-compatible mineral phases such as muscovite, calcium-rich resulted undersaturation zones. However, high fractional crystallization, abundance inner strongly peraluminous nature, total REE (<500 ppm), assemblage beryl, tourmaline, spessartine, columbite-tantalite, depletion Ba, Nb, Pb, Rb, Cs primitive mantle normalized multi-element plots suggest that beryl-bearing corresponds LCT family. Alkali with K/Rb values 30–150, Rb ~3000 ppm, >100 ranging 18–50, ~6000 500 Ta 65 ppm (3–5), indicate an intermediate-fractionated, beryl-type rare-element (REL) pegmatite. It probable >10 be considered guide mineralization region.