Genesis of the Kishan Pb-Zn mineralization, western Iran based on mineralogy, fluid inclusion and sulfur isotope evidences

Kishan lead-zinc deposit is one of the Malayer-Esfahan metallogenic belt deposits, located NW Arak, Markazi Province. The fluid inclusion microthermometry of the primary liquid-vapor bearing fluid inclusions trapped in the cogenetic quartz veins exhibited a homogenization temperature ranges from 140 and 272 °C (average 208.47 °C from 68 fluid inclusions), corresponding with the salinity of 10 to 22 wt.% NaCl equivalent (average 17.78 wt. % NaCl equivalent from 68 fluid inclusions) and density of 0.9 to 1.1 gr/cm3, illustrating the Irish-type characteristic in the Th versus salinity diagram. Additionally, following the mineralogical study and identifying three main mineralization stages of the Kishan deposit, including pre-, main- and late-stages, the sulfur isotope (δ34S) of six galena samples from the main mineralization stage were measured. The δ34S data varies between -3.76 and -5.36‰, which after temperature corrections by fluid inclusion microthermometeric data with average of 200 °C gave a narrow range of -0.98 to -1.76‰, consistent with the sulfide precipitation from the bacteriogenic sulfur-reduction. Consequently, the Irish-type metallogeny of Kishan deposit mostly involves with the intermittent mixing of the relatively cool and dense brines modified from the contemporaneous seawater with the circulating principal ore fluids containing leached metals from the beneath basement, i.e. metamorphosed shale and sandstone of Shemshak Formation. However, considering the extent of granitoieds in the area, recognizing of the plausible magmatic origin of sulfur and metal of the deposit also requires accurate dating of the igneous bodies and further studies.