Chalcophile Element Depletion in Lower Deccan Trap Formations and Implications for Cu-Ni-PGE Sulphide Mineralization in the Deccan Traps, India akin to those of Norilsk-Talnakh, Siberian Traps, Russia

AbstractChalcophile element depletion in the basalts of Nadezhdinsky Formation, Siberian traps, manifested by the Cu/Zr ratios (< 1) has been recognized as one of the most critical geochemical features in the ore genesis model of the world class Norilsk-Talnakh Ni-Cu-PGE sulphide deposit. Such a feature has been brought to light from the c.3 km thick lava pile of Deccan traps from the Western Ghats. In the lowest Jawhar, Igatpuri and Thakurvadi formations (c. 1.3 km) in the Kalsubai sub-group, where 62 out of the 65 samples have Cu/Zr ratios < 1. Such depletion is also shared by several dykes from the Narmada and Tapti rift zones that are considered to be the source regions for the flows.Sequential ore genetic processes envisaged for such depletion at Norilsk include, crustal contamination with country rocks, sulphur saturation, sulphide liquid immiscibility and finally enrichment in the tenor of Ni, Cu and PGE in the sulphides. Identification of such enriched zones in magma plumbing systems (chonoliths) and intrusions (dykes and sills) near the source regions within the Deccan traps is a huge challenge for exploration geologists in India.