Geochemical characteristics and implications of epidote in South Dulan and Vlaska exploration greenfield in north of Bor metallogenic zone, Serbia

Abstract

The Bor metallogenic belt in Serbia is a promising region for copper-gold (Cu-Au) resources, hosting numerous porphyry copper deposits, epithermal gold deposits and metallogenic prospects, such as the South Dulan and Vlaska exploration greenfield. Epidote alteration is integral to the propylitic and sodic-calcic alteration assemblages within this region. It is distinguished by the extensive occurrence of two primary epidote types: disseminated (Ep1) and veined (Ep2) epidote. In this study, comprehensive petrographic analysis reveals that in the propylitic zone, epidote mainly replaced hornblende (Ep1a) and plagioclase phenocrysts (Ep1b), coexisting with chlorite, apatite and titanite. In proximity to the potassic zone, epidote (E1c) coexists with biotite, while epidote (Ep2), chlorite, pyrite and chalcopyrite veinlets are observed near the ore body. Notably, Ep1 exhibits lower Fe and higher Mn contents in comparison to Ep2. Additionally, elements such as Ca, Al and Fe in Ep1a, and Ca, Fe, Mg, Mn and Ti in Ep1b, as well as Ca, Al, Fe and Mn in Ep1c, are introduced into the epidote through hydrothermal fluid interactions. Variations in trace element characteristics are evident among different epidotes. Specifically, Ep1a exhibits elevated Mg content (324–6050 ppm), Ep1b is notable for its high Na (22–942 ppm) and Sr (523–3075 ppm) contents, while Ep1c contains elevated K (24–445 ppm) and Na (41–103 ppm). Which suggest that disseminated epidote (Ep1) inherits the geochemical features from its precursor minerals. In comparison to disseminated epidote, epidote in veinlet exhibits higher Fe3+, Cu, Sn and REEs, along with lower contents of Pb, Sb and Sc, suggesting that these elements have been integrated into epidote through isomorphism substitution and influenced by fluids compositions, physical factors (temperature, pressure, etc.) and chemical parameters (speciation, pH, fO2, etc.), as well as mineral assemblages. Therefore, the trace element contents of Pb, Sb, Sc, Cu, Sn and REEs in epidote could serve as more appropriate indicators for mineral geochemistry in porphyry deposit hydrothermal centers.