Indicator Isotope-Geochemical Characteristics of Sulfides from the Satka Magnesite Ore Field (South Urals Province)

The stable enrichment of pyrite from magnesite ores in delta S-34 isotope (from 5.4 to 6.9aEuro degrees) compared with pyrite from the host (sedimentary and igneous) rocks was established in the classical Satka sparry magnesite ore field. Concretionary segregations of fine-grained pyrite in dolomite are depleted in the heavy sulfur isotope (delta S-34, from-9.1 to-5.8aEuro degrees). Pyrite from dolerite is characterized by delta S-34 values (-1.1 and 1.7aEuro degrees) close to the meteorite sulfur. The delta S-34 values in barite from the underlying dolomite horizon vary in the range of 32.3-41.4aEuro degrees. The high degree of homogeneity of the sulfur isotope composition in pyrite from magnesite is a result of thermochemical sulfate reduction during the syngenetic crystallization of pyrite and magnesite from epigenetic brines, formed during dissolution of evaporite sulfate minerals at the stage of early catagenesis of the Riphean deposits.