Petrogenesis, ore geology, geochemistry and geothermometry of the Jouzbon copper index, south-east Damghan

The Jouzbon Cu index (~1.5 wide and 100 meters’ length), at the south-southeastern parts of Damghan city belongs to the Torud–Chah Shirin volcanic belt. This belt contains calc-alkaline volcanic rocks. The Cu mineralization has occurred between two major faults, the Torud Fault at south and the Anjilu Fault at north. The volcanic and intrusive rocks in this belt include quartz-diorites, quartz-monzonites, dacites and andesites. These rocks show porphyritic, granular and poikilitic textures. The prevailing alteration phases of this region are characterized by sericitization, silicification, calcification, and propylitic alteration. The main mineralization phases of the Jouzbon region are dominanted by occurrence of the sulfides and oxide minerals including pyrite, chalcopyrite, galena, bornite and hematite. Secondary minerals such as covellite , chalcocite , malachite and iron hydroxide are also common. Geochemical observations show that the host rocks are related to a alumina-saturated calc-alkaline magma with volcanic arc (VAG) signature. Fluid inclusion studies on quartz testified a narrow homogenization temperature but a wide salinity, ranging from 130 to 190 ° C and 4 to 14.5 wt% NaCl equivqlent respectively. Geothermometry assay, based on morphology of pyrite crystals, yielded a temperature in the range of ~250°C for the alteration zone. The compiled data testified that mineralization probably has occurred at the depth of ~ 100 meters below the surface during the epithermal conditions, similar to the IOCG-type deposits.