Mineralogical and geochemical studies of Cu-Bi-Ag±W ores from Janjevo (Kosovo): Insights into the Bi sulfosalt mineralogy and the distribution of bismuth in base metal sulfides

Abstract

This work presents a mineralogical and geochemical study of Cu–Bi–Ag ± W ores from Janjevo in the Trepça Mineral Belt in Kosovo. This locality indicates a new type of Bi–Cu ± Au mineralization within the Kizhnica–Hajvalia–Badovc ore field, including Cu–Bi ± Ag ± As sulfosalts paragenesis previously not described in Kosovo and in this part of the Vardar Zone. Chemical composition of Bi– Pb ± Cu ±Ag and Cu – Bi ± Ag ± As sulfosalts, sulfides, and associated miner - als, as well as their paragenetic relationships and the distribution of minor and trace elements in main ore minerals, are discussed based on microscopy, microprobe, and laser ablation inductively coupled plasma mass spectrometry studies. The Cu–Bi– Ag ± W hydrothermal mineralization in Janjevo was formed during four stages: (1) Early base metal stage, (2) Bismuth stage, (3) Main stage, and (4) Late stage. The Early base metal stage is represented by pyrite, sphalerite I, chalcopyrite I, galena I, bournonite I, tetrahedrite I, siderite, and quartz. The Bismuth stage includes arsenopyrite I, löllingite, native bismuth, galena II, chalcopyrite II, tetrahedrite II, quartz, siderite, and Bi – Pb ± Cu ± Ag sulfosalts: bismuthinite, aikinite, krupkaite, cosalite, and gustavite. The Main stage is represented by chalcopyrite III, tetrahedrite group minerals (tetrahedrite and tennantite) III, galena III, sphalerite II, arsenopyrite II, bournonite II, and siderite. The Cu– Bi ± Ag ± As sulfosalts (pearceite, cupropearceite, wittichenite, and an unknown phase: AgCuBiS 3 ) associated with galena IV, siderite, and quartz were formed in the final low-temperature Late stage. The application of GGIMFis geothermometry on sphalerite gives the following sphalerite precipitation temperatures: 220–272 °C for sphalerite I and 160–190 °C for sphalerite II. Presented results show that in addition to numerous Bi sulfosalts in Janjevo Cu –Bi–Ag ± W ores, bismuth has been incorporated into base metal sulfides, as well as arsenopyrite. The main carrier of bismuth is arsenopyrite I, which has started the crystallization of the bismuth stage.