Geochemical, fluid inclusion and sulfur isotope studies of the Daghkesemen Au-bearing polymetallic deposit (Northwestern Azerbaijan) in Lesser Caucasus: Implications for ore genesis

The Daghkesemen Au-bearing polymetallic vein-type deposit, which is the most important ore deposit of the Kazakh graben located in the northwestern part of the Lesser Caucasus, is hosted by calc-alkaline volcanic rocks (andesite, dacite, basaltic trachyandesite, trachyandesite, rhyodacite and their pyroclastics), subvolcanic rocks (andesite porphyry, dolerite, albitophyre/rhyodacite porphyry), and volcanic breccias. The mineralization is commonly observed as gold-bearing quartz-sphalerite-galena-chalcopyrite veins. The Daghkesemen Au-bearing polymetallic deposit, mostly observed in the propylitic alteration, is commonly composed of primarily sphalerite, galena, chalcopyrite, pyrite, native gold, bornite and magnetite, and secondarily digenite, cerussite, covellite, chalcocite, malachite, azurite, hematite, jarosite, and anglesite. The Daghkesemen Au-bearing polymetallic deposit mostly comprises Zn, Pb, Cu, Au, Ag, Fe and Cd. Homogenization temperatures (Th) of the fluid inclusions in sphalerite and quartz range from 200.1 °C and 281.2 °C and 266.4–266.7 °C, respectively. The low salinities for the fluid inclusions in sphalerite and quartz show a range of 0.7–6.6 wt. % NaCl equivalent and 2.7 to 3.1 wt. % NaCl equivalent, respectively. Eutectic temperatures measured in the fluid inclusions vary between −27.4 and −18.2 °C, indicating H 2 O–NaCl–KCl system. The δ 34 S H2S values (−0.8 to −4.4‰) of sulfides (chalcopyrite, sphalerite, galena and pyrite) suggest a magmatic-hydrothermal origin for sulfur. The calculated sulfur isotopic geothermometer is value of 190 °C for sphalerite-chalcopyrite pair. The geochemical, mineralogical, sulfur isotopic and fluid inclusion data of the Daghkesemen Au-bearing polymetallic deposit suggest an intermediate sulfidation epithermal deposit associated with volcanic rocks. • The Daghkesemen Au-bearing polymetallic deposit is located in the largest porphyry-epithermal ore field of Lesser Caucasus (Azerbaijan). • Is hosted by calc-alkaline volcanic rocks. • associated with dominantly propylitic alteration and primarily composed of Zn, Pb, Cu, Fe, Au, Ag, Cd. • The calculated sulfur isotopic geothermometer (190 °C) consistent with microthermometric data (200–281 °C). • The ore-forming fluid was derived from a primarily magmatic source mixed with meteoric fluids. • Corresponds to an intermediate-sulfidation epithermal system.