Abstract
Major gold deposits of the world are often associated with carbonate alteration halos and -rich fluid inclusions. The source and transfer mechanisms of the fluids that concentrate gold within quartz vein systems are topics of debate. Here we investigate the C, O, and S stable isotopic composition of -rich fluid inclusions, and quartz, calcite, and sulphide minerals associated with the gold-quartz veins from the Wynad Gold Field, emplaced within the Proterozoic Moyar-Bhavani transcrustal shear system in the granulite facies terrain of southern India. Optical and microthermometric studies of fluid inclusions in auriferous quartz veins reveal that the dominant fluid is , with high (0.7-1.0) and low salinity (ca. 4-5 wt % NaCl equiv.). The carbon isotopie composition of extracted from fluid inclusions by crushing shows a remarkably narrow range of values, -4.1 to . Oxygen isotopie composition of the quartz veins range from +9.2 to . The (-9.1 to ) and (+ 7.6 to ) values of calcite from carbonate veins also define a distinctly uniform range. Sulphur isotopie values in pyrite, chalcopyrite, and pyrrhotite associated with gold display a range of +1.4 to . The carbon isotopie composition of fluid inclusions and carbonates from Wynad are identical to those reported for low-temperature carbonate alterations in high-grade terrains induced by mantle-derived . The narrow spread in isotopie values associated with veins traversing compositionally variable host rocks is consistent with a model involving derivation of by degassing of underplated mantle-derived magmas and transfer of juvenile to higher crustal levels through felsic magmatic conduits. We envisage a common link between Proterozoic influx and incipient charnockite formation, carbonate alteration, and gold mineralization in this terrain.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call