Trace elements in pyrite from AuAg epithermal deposits of Kamchatka, Russia: Comparison with geochemical features of mineral systems

Trace elements in pyrite from adularia-sericite (LS type) deposits (Aginskoe, Baranyevskoe, Rodnikovoe, and Kumroch) and acid-sulfate (HS type) deposits (Maletoyvayam) of AuAg epithermal systems in Kamchatka, Russia, were analyzed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In most of the studied deposits, the concentration of Au in pyrite did not exceed 10 ppm. The Au/Ag ratio in pyrites from most deposits is less than 1, except for the Aginskoe deposit, in which pyrite is notably enriched in Au (up to 120 ppm), similar to the Au-rich ores of this deposit with an Au/Ag ratio >1. The concentration of copper (Cu) in pyrite reaches 10,000 ppm in both deposit types. However, Cu is positively correlated with Ag only in the adularia-sericite type deposits (Kumroch, Rodnikovoe, and Aginskoe), aligning with the presence of Ag-containing sulfosalts in these deposits. The neutral and alkaline conditions in the adularia-sericite deposits contribute to an enrichment of the ore-forming system in As, which is significantly concentrated in pyrite (up to 10,000 ppm). Moderate concentrations of Te (up to 100 ppm) were found in pyrite from deposits where tellurides are typically present, with the exception of the Te-depleted pyrite (<10 ppm) from the Rodnikovoe deposit, where telluride minerals were absent. In contrast, the acidic conditions at the Maletoyvayam deposit led to the enrichment of the ore system in Se, Te, and Sb, facilitating the incorporation of these elements into pyrite (up to 10,000 ppm Se, and 1000 ppm each for Te and Sb), as well as the formation of minerals containing these elements. Lead and zinc are moderately present in the pyrite from all deposits, while galena and sphalerite are commonly found only in the Kumroch deposit; their presence may be limited by structural factors. The trace elements found in pyrite, either as solid solutions or nanoclusters, play an important role in the formation of ore assemblages in all studied epithermal AuAg deposits in Kamchatka. The geochemical specialization of ore-forming systems is the main factor controlling these processes, while physical and chemical conditions of ore deposition also significantly influence the enrichment of these trace elements in pyrite.