Intermediate-sulfidation epithermal base metal mineralization in the Kourcheshmeh deposit (SW Takestan): Constraints on geology, mineralization, and geochemistry

Kourcheshmeh Pb-Zn-Cu deposit is located 40 km southwest of Takestan (Qazvin province) and west of the Mardabad-Bouinzahra volcanic belt. The mineralization occurred as Pb-Zn-Cu-bearing quartz veins hosted by early-middle Eocene tuff and lava strata and show a close spatial relationship with the middle Eocene pyroxene quartz monzodiorite body. The main ore vein ranges from 70 to 200 meters long, and 0.5 to 2 meters thick. Pyrite, chalcopyrite, galena, sphalerite, and tennantite-tetrahedrite, accompanied by minor pyrolusite and psilomelane, are the main ore minerals; quartz, calcite, siderite, barite, and sericite-illite are gangue minerals. Goethite, cerussite, smithsonite, malachite, and covellite are formed by supergene processes. The ore minerals formed as disseminated, vein-veinlets, brecciated, comb, crustiform, colloform, plumose, and vug infill textures. Six stages of mineralization can be distinguished at Kourcheshmeh, where Pb-Zn-Cu mineralization occurred as quartz-pyrite-chalcopyrite-galena-sphalerite ± tennantite-tetrahedrite veins and breccias in the second stage. Wall-rock alteration comprises silicification, intermediate argillic, carbonate, and propylitic alteration. Chondrite–normalized trace elements and REE patterns of ore samples, pyroxene quartz monzodiorite body, and fresh host acidic crystal tuff are comparable. This specifies that alteration and leaching of elements from the host volcanic rocks are involved in mineralization. Features of the Kourcheshmeh Pb-Zn-Cu deposit are similar to the intermediate-sulfidation type of epithermal deposits.