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Reconstruction of Physicochemical Environment of Hydrothermal Mineralization at M alanjkhand Copper Deposit, Central I ndia: Constraints from Sulfur Isotope Ratios in Pyrite, Molybdenite and Chalcopyrite
Author(s) -
Panigrahi Mruganka K.,
Pandit Dinseh,
Naik Rajesh K.,
Ishihara Shunso
Publication year - 2013
Publication title -
resource geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 43
eISSN - 1751-3928
pISSN - 1344-1698
DOI - 10.1111/j.1751-3928.2012.00214.x
Subject(s) - molybdenite , chalcopyrite , pyrite , geology , fluid inclusions , pyrrhotite , sulfide minerals , geochemistry , sulfur , sulfide , mineralogy , mineralization (soil science) , hydrothermal circulation , copper , chemistry , seismology , organic chemistry , soil science , soil water
δ 34 S values of pyrite, molybdenite and chalcopyrite were determined from the M alanjkhand copper deposit. These minerals constitute the primary sulfide phases that were deposited after the initial magnetite deposition in the main orebody and host granitoid. Pyrite exhibits a depleted range of values (−2.63 to −0.56‰), chalcopyrite, a very narrow range of values around zero (−0.039 to 0.201‰) and molybdenite furnishes a range of enriched values (0.68 to 1.98‰). On back calculation of the δ 34 S values of H 2 S in the fluid from which the minerals were likely to have precipitated, using standard expressions for equilibrium fractionation at the temperature range obtained from fluid inclusion and mineral fluid equilibria, it is observed that H 2 S in the fluid at pyrite deposition was depleted and gradually became enriched towards molybdenite and chalcopyrite deposition. This trend is best explained as being due to inorganic reduction of SO 4 2 − in the fluid and is very much in agreement with the paragenetic sequence indicating increasing activity of H 2 S in the fluid. The very restricted range in the δ 34 S values of sulfide minerals in the fluid does indicate a single, possibly magmatic, source of sulfur that also agrees well with the earlier deduced model of genesis of the deposit as an ancient geothermal system associated with granitic magmatism.