Auriferous mineralization in the Sakoli Group,central India,with particular reference to sulphide-bound gold

Gold mineralization in the Pular-Parsori-Thutanbori belt of the Sakoli Group in central India is hosted predominantly by a felsic volcanic suite of rocks and is associated with quartz-sulphide ±carbonate veins. Both free and submicroscopic or invisible forms of latticebound gold occur. The free gold is found within the shear zone, as either disseminated or fracture-controlled grains within sulphides. Major opaque minerals in this gold-bearing belt include arsenopyrite, pyrrhotite, pyrite, chalcopyrite, sphalerite, galena, molybdenite, magnetite, hematite and scheelite. A three-stage paragenesis been established for these minerals.

Mineral chemical analyses of the sulphides reveal the presence of sulphide-bound gold within the belt—the first time such occurrences have been identified in central India. Quantitative spot analyses of individual grains of sulphide indicate high concentrations of lattice-bound gold, which scanning electron micrographs show to be heterogeneously distributed. The substitution of Fe3+ by Au3+ in the lattice structure of the sulphides is postulated as the probable mechanism by which the gold became concentrated.