Copper-Gold Skarn Mineralization at the Karavansalija Ore Zone, Rogozna Mountain, Southwestern Serbia

Karavansalija ore zone is situated in the Serbian part of the Serbo-Macedonian magmatic and metallogenic belt. The Cu-Au mineralization is hosted mainly by garnet-pyroxene-epidote skarns and shifts to lesser presence towards the nearby quartz-epidotized rocks and the overlying volcanic tuffs. Within the epidosites the sulfide mineralogy is represented by disseminated cobalt-nickel sulfides from the gersdorfite-krutovite mineral series and cobaltite, and pyrite-marcasite-chalcopyrite-base metal aggregates. The skarn sulfide mineralization is characterized by chalcopyrite, pyrite, pyrrhotite, bismuth-phases (bismuthinite and cosalite), arsenopyrite, gersdorffite, and sphalerite. The sulfides can be observed in several types of massive aggregates, depending on the predominant sulfide phases: pyrrhotite-chalcopyrite aggregates with lesser amount of arsenopyrite and traces of sphalerite, arsenopyrite-bismuthinite-cosalite aggregates with subordinate sphalerite and sphalerite veins with bismuthinite, pyrite and arsenopyrite. In the overlying volcanoclastics, the studied sulfide mineralization is represented mainly by arsenopyrite aggregates with subordinate amounts of pyrite and chalcopyrite. Gold is present rarely as visible aggregate of native gold and also as invisible element included in arsenopyrite. The fluid inclusion microthermometry data suggest homogenization temperature in the range of roughly 150-400°C. Salinities vary in the ranges of 0.5-8.5wt% NaCl eq for two-phase low density fluid inclusions and 15-41wt% NaCl eq for two-phase high-salinity and three-phase high-salinity fluid inclusions. The broad range of salinity values and the different types of fluid inclusions co-existing in the same crystals suggest that at least two fluids with different salinities contributed to the formation of the Cu-Au mineralization. Geothermometry, based on EPMA data of arsenopyrite co-existing with pyrite and pyrrhotite, suggests a temperature range of 240-360°C for the formation of the arsenopyrite, which overlaps well with the data for the formation temperature obtained through fluid inclusion microthermometry. The sulfur isotope data on arsenopyrite, chalcopyrite, pyrite and marcasite from the different sulfide assemblages (ranging from 0.4‰ to +3.9‰ δ³⁴S_CDT with average of 2.29 δ³⁴S_CDT and standard deviation of 1.34 δ³⁴S_CDT) indicates a magmatic source of sulfur for all of the investigated phases. The narrow range of the data points to a common source for all of the investigated sulfides, regardless of the host rock and the paragenesis. The sulfur isotope data shows good overlap with that from nearby base-metal deposits; therefore the Cu-Au mineralization and the emblematic base-metal sulfide mineralization from this metallogenic belt likely share same fluid source.