GEOCHEMICAL CHARACTERIZATION OF TUNGSTEN-BEARING GRANITES FROM RAJASTHAN, INDIA

Tungsten mineralization in Rajasthan (northwestern India) is genetical ly associated with granites of Late Proterozoic age. These granites ar e emplaced on the western margin of the Delhi fold belt. In order to i nvestigate possible geochemical parameters for regional exploration an d to delineate areas with tungsten potential a comparative study of th e geochemical results for the granites associated with tungsten minera lization (Tungsten granites) and those which are not related with any mineralization (Barren granites) in the same or nearby areas from Raja sthan, was undertaken. Tungsten granites are found enriched in SiO2, t otal alkalis and are depleted in CaO, FeO, TiO2 and MgO. The Tungsten granites in general have a higher concentration of W than the Barren g ranites. They are also enriched in Rb, Li, Sn, Nb, B, Be and are deple ted in Ba and Sr and are highly differentiated. Higher values for Rb/S r, Li/K and Ba/Sr and lower values of K/Rb, Ba/Rb and Mg/Li of Tungste n granites in comparison with Barren granites were found to be the mos t significant discriminators. A Geochemical Characterization Index (GC I) is proposed using the trace element discriminators for characterizi ng Tungsten granites and Barren granite. The GCI has a positive value for the Tungsten granites while the Barren granites have negative valu es. The proposed Geochemical Characterization Index is useful for deli neating the granites genetically and spatially associated with tungste n mineralization and hence can be used as an exploration tool. (C) 199 7 Elsevier Science B.V.