Fluid inclusion and O-S stable isotope studies in determining the genesis of gold mineralization in the Hesar mining area, southwest Mianeh, NW Iran

Hesar gold mining area is located in Iran Alborz-Azerbaijan zone. The predominant lithology in the mineral range is volcanic, subvolcanic, and sedimentary rocks of the Cenozoic period, which include volcanic and pyroclastic rocks, andesite-trachyandesite, basalt, eicombrite, and tuffs of the Eocene age and related to the Laramid orogenic phase under the influence of Laramide. Expansion phase of volcanic lava that erupts from several fissures and emerges in the form of delirious dykes and floods and stocks, mainly dacite, rhyodacity with Oligocene age, and alterations related to these masses such as silicification, pyritization and caudal formation Major mineralization in the study area includes pyrite, goethite, magnetite and gold, which is mineralized in two phases and is mainly selective and dispersed. Gold mineralization is the result of the decomposition of pyrite and arsenic pyrite, which is free in the field. The rock has been found to be related to the second phase of volcanic and semi-volcanic outcrops of the Oligomocene age. The results obtained from microscopy studies of fluid shortcuts in quartz mineral indicate that the homogenization temperature varies in the range of 140 to 260 ° C and also the melting temperature of the last ice crystal changes from -0.1 to -9. ° C and salinity is between 0.18 to 14% by weight equivalent of NaCl with a frequency range of 2 to 6% by weight equivalent of NaCl.