Trace elements in pyrite from the Čukaru Peki porphyry Cu–high-sulfidation deposit, Serbia: implications for ore evolution in a polyphase hydrothermal system

Abstract

Čukaru Peki is a recently discovered porphyry- high-sulfidation Cu-Au deposit located 5km south of the mining town of Bor in east Serbia. Three styles of mineralization are distinguished in the Čukaru Peki system: a high-sulfidation type with massive sulfides (named the Upper zone), a porphyry type (named the Lower zone) and a transition type (between porphyries and massive sulfides). This study investigates the concentration and distribution of trace elements in pyrite from these three mineralization zones of Čukaru Peki. The high-sulfidation pyrite contains elevated concentrations of V, Mn, Ni, Cu, As, Mo, Ag, Cd, In, Sn, Sb, Au, Hg, Tl, Pb and Bi, compared to pyrite from the porphyry zone. The porphyry zone pyrite contains elevated concentrations of Co and Se. The sample from the transition zone contains concentrations between the two other zones, with the exception of the relative enrichment of Co and Ag. This research also aims to separate different stages of ore deposition. The porphyry stage contains several types of veins: quartz A veins, quartz B veins, pyrite D veins, magnetite veins, purple anhydrite veins, sulfide veins and orange anhydrite veins. The high sulfidation stage also formed in several stages: pyrite1, pyrite-enargite veins, pyrite-covellite veins, pyrite2 veins and calcite-anhydrite veins. There are distinct differences between various vein generations found within each zone, notable examples are the enrichment of Se in quartz B veins pyrite and Cu in sulfide veins, compared to other veins from porphyry zone veins and the enrichment of several trace elements (Cu, Mo, Ag, Cd, In, Sn, Sb, Au, Hg, Tl, Pb and Bi) in pyrite from the Py-cov veins in comparison to the other high-sulfidation veins. The trace element data also indicates a change in fluid compositions; the earlier fluids responsible for the porphyry zone mineralization showing a slightly more magmatic fluid signature (higher Co/Sb and Se/As values) and the later high-sulfidation fluids bearing a more typical epithermal trace element signature, which indicates cooling and diluting of fluids. Some of the porphyry zone pyrite crystals (from B-type veins and Purple anhydrite-veins) contain elevated concentrations of elements attributed to the high-sulfidation zone (e.g. Cu, Ag, Cd, In, Sn, Pb and Bi), which suggests that these veins were affected by later high-sulfidation fluids.