Determination of Alishar Cu index (Markazi province) formation conditions using mineralography and fluid inclusions data

The Alishar Cu-Au index is located in the Markazi province within the Uromieh-Dokhtar magmatic belt. The mineralized zone is hosted by andesitic to andesite basalt lava units، andesitic-andesite basalt tuff and rhyolitic to dacitic tuff (Eocene-Oligocene). The area is affected later by young granodiorite and monzodiorite plutonic units (Oligo-Momiocene). As a result of hydrothermal alterations، phyllic and propylitic alterations as well as kaolinitization and silicification developed in the area. In addition، Cu -Au mineralization has been introduced into the area، mainly associated with silicic veins. Based on geochemical data the Cu and Au contents of the samples are about 0. 5% and 0. 3 ppm respectively. Also، the Bi content of the studied samples is about 0. 5 ppm. The index comprises oxidation، hypogene and supergene zones and contains chalcopyrite، pyrite، chalcocite، magnetite، hematite، goethite and malachite. Fluid inclusion studies of the samples taken from silicic veins show that the homogenization temperature and salinity vary between 200 to 300 °C and 21. 6% wt NaCl respectively. On the base of obtained data، it can be concluded that the dominant mechanism for mineralization is the mixing of hydrothermal solutions with meteoritc waters. Geological، mineralogical and fluid inclusion investigations have demonstrated that mineralization in this area is correlated with other IOCG deposits in the world.