Geochemistry and Tungsten Metallogeny of the Balda Granite, Rajasthan, India

Abstract

Balda granite occurs along the western margin of the middle Proterozoic South Delhi Fold Belt. It is a medium grained leucogranite associated with tungsten mineralisation. Wolframite mineralisation is confined to pneumatolytic quartz veins and greisenised pegmatites located mainly along shear zones within Balda granite and neighbouring metasediments. Geochemistry of Balda granite suggests that it is highly evolved, peraluminous and volatile -rich granite formed from the melt derived by partial melting of metasediments. Borates and fluorides in various complexes favoured the concentration of W in the melt, whereas sodium cations, chlorides and phosphates were the carrier of tungsten in fluid. The shear zones developed within Balda granite and neighbouring metasediments provided the channelways for fluid movement and deposition of wolframite.