Nature of ore forming fluids, wallrock alteration and P-T conditions of gold mineralization at Hira-Buddini, Hutti-Maski Greenstone Belt, Dharwar Craton, India

Gold mineralization at Hira-Buddini deposit in Hutti-Maski Greenstone Belt of Dharwar Craton, India is associated with quartz veins and hydrothermal alteration formed during a brittle-ductile deformation episode. The vein minerals (quartz and plagioclase) exhibit microstructures of dynamic recrystallization/intracrystalline deformation. Estimated temperature and pressure condition during mineralization is around 500 degrees C and 2.05-4.36 kbar, respectively. Carbonic inclusions are the most abundant type of fluid inclusions found in quartz grains of mineralized veins. Such abundance of carbonic inclusions must be due to preferential loss of water from original fluid inclusions during intracrystalline deformation of quartz. Rock-fluid interaction led to enrichment of SiO2 (in the form of quartz veins), K, Pb, S and LOI in the auriferous lode. It is inferred that the hydrothermal fluids involved in gold mineralization were of both metamorphic and magmatic origin. Deposition of gold has been attributed to phase separation as well as wall rock sulfidation.