Kuh-e Dom Fe–Cu–Au prospect, Anarak Metallogenic Complex, Central Iran: a geological, mineralogical and fluid inclusion study

Abstract

The Kuh-e Dom Fe–Cu–Au prospect is located in the Urumieh-Dokhtar Magmatic Belt, and is characterized by copper–iron oxide and gold veins, stockworks and breccias hosted by the Eocene Kuh-e Dom arc intrusion. Mineralization is located within NE–SW to WNW–ESE sinistral faults and likely formed in a subduction-related continental margin that is typical of IOCG deposit systems. The deposits have a distinct metal composition of Fe, Cu, Bi, Co, Mo and LREE with gold (up to 3 g/t), and the mineral assemblages are quartz, hematite, pyrite, chalcopyrite, emplectite, magnetite, free gold, calcite, barite, chlorite, and tourmaline. Three paragenetic stages of mineralized quartz veins are distinguished in the Kuh-e Dom prospect, including: (i) hematite-bearing quartz veins, (ii) quartz-sulfide stockwork and breccia veins, and (iii) quartz-calcite±sulfide infilling veins. Sodic (albitization), potassic, and quartz–calcite±chlorite pervasive alterations are commonly associated with these three mineralization stages. Three types of fluid inclusions have been identified at Kuh-e Dom, including: aqueous two-phase (H2O−NaCl−CaCl2±FeCl2), halite-saturated aqueous (H2O−NaCl±KCl), and CO2-bearing (H2O–CO2±CH4 and CO2±CH4) fluid inclusions. A hypersaline (~35 wt% NaCl equiv.), aqueous magmatic fluid was released at about 400 °C and a pressure of nearly 4 kbar, forming early hematite-bearing quartz veins. These high salinity fluids were progressively diluted further away from Kuh-e Dom intrusion due to substantial input of meteoric water and mixing with the magmatic components during the middle and late stages of mineralization. The mineralogy, alteration, and fluid composition of the Kuh-e Dom Fe–Cu–Au prospect compared well with Fe oxide Cu–Au (IOCG) deposits worldwide.