A geochemical study of gersdorffite from the Trepça Mineral Belt, Vardar Zone, Kosovo

This work presents a textural and chemical study of gersdorffite from numerous small occurrences of hydrothermal Pb–Zn + (Ni–As–Sb) mineralization from Trepça Mineral Belt (broad area of Stan Terg and Kizhnica–Hajvalia–Badovc ore field) hosted in hydrothermally altered serpentinites (listvenites). Mineral associations, textural relations and substitutional trends of gersdorffite recognized in Kizhnica, Mazhiq, Melenica, Vllahia and Selac are discussed based on microscopy and microprobe studies. The two types of paragenetic sequence with nickel mineralization are distinguished in studied localities: Ni–Fe–Co sulfides → Ni sulfarsenides and sulfantimonides (in Kizhnica–Badovc and Melenica) and Ni sulfarsenides → Ni–Fe arsenide and diarsenide → ± Ni sulfides (Vllahia and Selac). Various substitution trends in studied GUS are detected: Fe + Co/Ni (all localities, except Selac); As/Sb – gersdorffite–ullmannite series (Kizhnica, Mazhiq, Vllahia VLX) and As + Sb/S (Selac and Vllahia VL4). Based on As/S ratio, two different hydrothermal fluids were distinguished: narrow range and low As/S values (Kizhnica, Mazhiq, Melenica, Vllahia VLX), which suggest decreased As activity, mixing in the proximity of deposition site (Kizhnica, Mazhiq), broad range and high As/S values: increased As activity and disequilibrium crystallization (Selac, Vllahia VL4).