Organic and inorganic geochemistry of gold mineralisation at the Zloty Stok,Southwest Poland

Abstract

Inorganic and organic geochemical data obtained from contact-metasomatic and skarn-like mineralisation and associated country rocks from the Zloty Stok Au–As deposit in Southwest Poland have been studied. Magnetite-rich calcite-dolomite marbles have the highest total organic carbon content of the rocks studied. Organic matter consists of solid bitumen, with a minor extractable fraction composed mainly of low molecular weight aromatics. There are positive correlations between organic matter and Fe₂O₃ and MgO content, suggesting remobilisation of organic matter by the hydrothermal fluids during serpentinisation processes. Results of the organic geochemical and isotope studies suggest that the hydrocarbons were formed by thermal and later hydrothermal alteration of indigenous organic matter. The ranges of δ³⁴S values of sulphides show that in Au-rich arsenopyrite and pyrrhotite, most of the sulphur may have originated from a magmatic source. However, some of results indicate a contribution from isotopically heavier sulphur, most probably associated with fluids derived from the metamorphic sedimentary environment. Rare earth element patterns of the mineralised samples point to a granitic source of the studied orebodies.