Geological Constraints on the Genesis of Jagpura Au-Cu Deposit NW India: Implications from Magnetite-Apatite Mineral Chemistry, Fluid Inclusion and Sulfur Isotope Study

Abstract

The Jagpura Au-Cu deposit is situated within the Aravalli craton in the northwestern part of India. In the present work, petrography, mineral chemistry, fluid inclusion and sulfur isotopic compositions were used to study the Jagpura Au-Cu deposit. The ore mineral association of the deposit is arsenopyrite, loellingite, chalcopyrite, pyrrhotite and pyrite, along with native gold, magnetite and apatite. The gold fineness ranges from 914–937‰ (avg. 927‰). The presence of Au-Bi-Te phases, pyrite (>1 Co/Ni ratio), magnetite (≥1 Ni/Cr ratio, <1 Co/Ni ratio) and apatite (>1 F/Cl ratio) suggest the hydrothermal origin Au-Cu mineralization. A fluid inclusion study indicates the different episodes of fluid immiscibility with the homogenization temperatures varying between 120–258 °C and salinities range within the 8.86–28.15 wt% NaCl eq. The sulfur isotopic composition of sulfides varies from 8.98 to 14.58‰ (avg. 11.16‰). It is inferred that the variation in the sulfur isotopic compositions of sulfides is due to the cooling and dilution of the metalliferous fluid of mixed origin, derived from the basement meta-sedimentary rocks and the high saline basinal fluid. The iron oxide-copper-gold-apatite associations, structural control of mineralization, pervasive hydrothermal alteration, fluid salinity and sulfur isotope compositions indicate that the Jagpura Au-Cu deposit is similar to the iron oxide-copper-gold (IOCG)-iron oxide-apatite (IOA)types of deposits. Based on the ore geochemistry and the trace elements systematic of magnetite, the deposit is further classified as an IOCG-IOA type: IOCG-Co (reduced) subtype.