Sources of Sulfur for Sulfide Mineralization in the Archean Rocks of the Sharyzhalgai Uplift of the Siberian Craton Basement (from Multi-Isotope Data)

Abstract

Abstract —We present results of study of sulfide ore occurrence in highly metamorphosed (granulite facies) Archean rocks of the Siberian craton basement. The host rocks and ore minerals are briefly described, and new data on the multiple sulfur isotope (δ33S, δ34S, Δ33S) composition of sulfides are presented. Application of high-resolution analytical methods enabling the assessment of the sulfur isotope behavior in situ made it possible to reveal mass-independent fractionation of sulfur isotopes in the rock samples. The isotopic composition of sulfur in the sulfides indicates its inflow from several sources, including the ancient Archean atmosphere, where primary sulfur has passed through a cycle of fractionation. Despite the high-gradient metamorphism, the subsequent ultrametamorphic and post-ultrametamorphic transformations accompanied by a change in the primary mineral composition of rocks and by chemogenic fractionation of sulfur, the signature of the sedimentary source of sulfur in sulfide ores has been well preserved. Analysis of the chemical composition of rocks and ore minerals and of sulfur isotopes has led to the conclusion that the studied rocks are metamorphosed Late Archean analogs of black shales and the sulfide mineralization is of stratiform pyrite type.