Investigation of ore mineralization and fluid inclusions of the Kamar-Gov district, south Hashtjin, Ardabil Province, NW Iran

The Kamar-Gov study district is located south of Hashtjin city in the Ardabil Province (NW Iran). The geological units in this district include lavas (with composition of basaltic trachy-andesite to rhyolite), sub-volcanic rocks (as dyke and stock with composition of porphyritic trachy-andesite and trachyte) and crystal, vitric (lithic) tuffs (intermediate and felsic composition). Extensive zones of silicic, sericitic-argillic, advanced-argillic, and chloritic alteration have formed in these rocks. Pyrite is the prevalent metal mineral in the study area and approximately extended in all rock units. Besides pyrite, chalcopyrite, chalcocite, galena, sphalerite, hematite, and magnetite are also present. Covellite, digenite, and goethite are supergene minerals. Ore minerals have formed in crystal, vitric tuff and rhyolite as veinlet, dissemination, strata-bound dissemination, and inside silicic veins/veinlets. Three types of primary fluid inclusions are present within quartz minerals of silicic veins/veinlets and accompanied by disseminated ore minerals, including liquid-rich two phases, vapor-rich two-phases, and salt-saturated three-phase fluid inclusions (liquid, vapor, and halite + sylvite). Micro-thermometric analysis of these fluid inclusions shows the salinity of 1.05-14 wt% NaCl equivalents with the highest frequency of homogenization temperatures between 200 and 300 °C. The ore formation type is similar to intermediate sulfidation epithermal deposits, based on features like the vein-veinlet shape of ore mineralization, colloform and crustiform textures, base metal mineralization, the mineral assemblage of kaolinite – muscovite – pyrite ± sphalerite, intermediate salinity and temperature of the fluid, and probable effect of the boiling process.