Investigation of mineralization and fluid inclusions of the Lapeh-Zanak copper deposit, Central Alborz zone, Iran

The Lapeh-Zanak copper deposit is located about 15 km east of Tehran, in the southern part of the Central Alborz Zone. The rock units exposed in this area include a sequence of volcanic and pyroclastic rocks (basalt, andesite, trachy-andesite and dacitic and vitric tuff) belonging to the Fajan Formation with the Paleocene-Lower Eocene age, which are cut by subvolcanic igneous masses with a composition of micromonzodiorite-gabbro. Copper mineralization in the Lepeh-Zanak deposit occurred in the form of quartz veins-veinlets (± carbonate and barite) along with silicic, argillic, carbonate and propylitic alterations in andesite-trachyandesite rocks. Vein-veinlet and breccia structures and textures are very common in the copper- bearing ore in this deposit. The mineralogy of ore is simple and includes primary minerals of pyrite, chalcopyrite, magnetite, hematite and rutile, which are accompanied by secondary minerals such as digenite, covellite, malachite, and iron hydroxide compounds. The fluid inclusion studies of quartz and barite minerals in copper-bearing ores and barite veins indicate that majority of primary inclusions are two-phase liquid-rich (L+V). Microthermometric studies show that the homogenization temperatures in quartz and barite vary in the range of 100 to 198 and 110 to 207 °C, respectively. Salinity in the primary inclusions of these two minerals shows the range from 0.88 to 8.55 and 4.96 to 7.86% wt% NaCl eq., respectively. Salinity in quartz and barite minerals is in the range of 0.88 to 8.55 and 4.96 to 7.86 wt% NaCl eq., respectively. Based on the results of microthermometric of fluid inclusions, cooling and dilution of hydrothermal fluids with atmospheric waters are the main reasons for the deposition of minerals in the studied deposit. The combination of the results obtained from geological, mineralogical, alteration and fluid inclusions reveals that the Lapeh-Zanak copper deposit has most similar to low-intermediate sulfidation epitermal-type deposits.