Geology and Geochemistry of Topaz Granite and Associated Wolframite Deposit at Degana, Rajasthan

Post-Delhi acid magmatism at Degana has yielded three intrusive bodies of topaz granite, the earliest one emplaced within phyllite of Delhi Supergroup and the other two successively in the core of previous intrusive, along with two generations of aplites. Wolframite mineralisation has occurred at two different stages during the magmatism: (1) greisen-bordered vein-type ore bodies hosted by the earliest granite intrusive and adjoining phyllite rcpresent the first stage, and (2) stockwork ore bodies hosted by an intrusion breecia developed at a later stage following the emplacement of other two granite bodies. Presence of topaz, Li-mica and fluorite is a characteristic feature of these granites and wolframite deposits. The granites are strongly peraluminous and geochemically specialised with enrichment of Li, F, Rb and depleted in Sr, K-As dating of zinnwaldite from wolframite bearing lode indicates an age of 860±25 Ma.