ROCK-WATER INTERACTION AND EVOLUTION OF SULFIDE ORES IN THE LATE ARCHEAN CHITRADURGA GREENSTONE-BELT OF SOUTHERN INDIA

Sulphide ore mineralization developed in proximity to iron formations in a cyclic volcano-sedimentary sequence that forms the offshore part of the late Archaean intracratonic basin of the Chitradurga greenstone belt, south India. The chemistry of volcanic suite attests to an exte nsive rock-water interaction resulting in exchange of Si and Na for di valent cations, including Cu, Pb and Zn. The exchange took place durin g hydrothermal alteration of basalt prior to its involvement in region al deformation and metamorphism. A hydrothermal convection system extr acted Cu, Zn and Pb from sea-floor basalts during a static phase of ev olution of the Chitradurga basin and developed the stratabound ore dep osit within the pyroclastics and the stringer ores below.