Copper Mineralization in Machanur Area of the Dharwar Craton, Karnataka

Copper mineralization in Machanur is confined to the fracture and breccia zone (shear zone) traversing mainly pink porphyritic granite of the Closepet granite suite (2,400-2,000 my.) including minor diabase dykes and pegmatites, The mineralization is fractule-controlled cavity filling epiigenetic hydrothermal type. The associated wall-rock alterations are chloritization, saussuritizalion, sericitization and silicification of the host-rocks. The  mineralization consists essentially of chalcopyrite and pyrile with subordinate bornite, chalcocite, covellite, digenite and linnaeitc. Native copper occurs but rarely. Hematite(specularite) and magnetite are commonly associated with the mineralization. Three stages of mineralization have been inferred. It is suggested that the second stage has been dominated by precipitation of chalcopyrite. The paragenetic scquence is suggestive of high fO₂ condition in fluid at the beginning and progressive increase of Cu/Fe ratio and high fS₂ condition in fluid during the main Cu deposition stage.