Constraints on the genesis of the Proterozoic bornite dominated copper deposit from Nim ka Thana, western India: An IOCG perspective

摘要

The copper mineralization at the southeastern fringe of the Khetri copper belt in western India is primarily hosted within the metapelites and dolomite units of the Mesoproterozoic Ajabgarh Group of rocks. The copper mineralization is well exposed along a NE-SW trending basinal part around Nim ka Thana area where a few of the prospects namely Dokan, Baniwala-ki-Dhani, Dariba, and Nanagwas primarily consist of abundant bornite, chalcopyrite, covellite, digenite, and chalcocite as disseminated phases hosted within a wide-ranging litho units and along quartz-calcite-barite veins. An integrated approach has been adopted to understand the metallogenetic evolution of this bornite dominated copper mineralization. delta C-13(V-PDB) and delta O-18(V-SMOW) results of the carbonate veins ranging from 0.57 parts per thousand to -3.75 parts per thousand and delta O-18 range from 15.01 parts per thousand to 20.74 parts per thousand respectively suggest the influx of hydrothermal fluid in shaping up the deposit. delta C-13 (CO2) of the ore-bearing fluid ranges from -1.67 parts per thousand to 2.65 parts per thousand and delta O-18 (H2O) from 7.11 parts per thousand to 12.84 parts per thousand respectively also suggest the input of hydrothermal source. The S-isotopic values of Cu-mineralized barite samples range between 16 parts per thousand and 20 parts per thousand, which are lower than that of seawater (delta S-34 parts per thousand = 2022 parts per thousand). This provides the evidence that the barite mineralization could have formed from the hydrothermal fluid that is cogenetic with the late-stage mineralization in a phase-wise separation as an associated mineral assemblage in the system progressively enriching the bornite-rich copper deposit.