Epithermal base metal veins of Gomish-tappeh Zn-Pb deposit are located 30 km southwest of Qeydar, Znajan district, in northwestern part of Orumieh-Dokhtar volcano-plutonic zone, Iran. The oldest outcrops in the area are Upper-Cretaceous alternatives of grey argillaceous limestone and shale which are overlain by an Oligo-Miocene volcano-sedimentary sequence. Volcano-plutonic activity occurs in Pliocene as rhyodacitic subvolcanic domes and dacitic volcanics. The rocks in the area have a calc-alkaline nature in a VAG basin.
Two aspects of hydrothermal activity are present: hydrothermal alteration of the rocks and ore deposition. The epithermal event was characterized by hydrothermal brecciation when delicate to coarsely banded vein material was precipitated.
The metalliferous veins form parallel systems generally with constant northeast-southwest trend. The highest ore contents are observed within the fault and alteration zones. Host rock of mineralization is rhyolite to rhyolitic tuff. The mineralization at the deposit consists of:
1- Silicic-sulfidic veins, including quartz, pyrite, chalcopyrite, galena, sphalerite, bornite, digenite and covellite.
2- Silicic, sulfidic and carbonate veins comprising quartz, calcite, pyrite, galena and minor chalcopyrite.
Secondary minerals include malachite, azurite, chalcocite, covellite, cerussite, anglesite, smithsonite, hemimorphite, hydrozincite, siderite and Fe-Mn oxides. The vein textures are described as open space filling, crustiform, banded vein, brecciated and comb textures.
The varying extent of the hydrothermal process is reflected in various mineral assemblages that characterize successive alteration zones and different types of hydrothermal alteration. These types range from alteration, represented by silicic, argillic, sericitic, carbonate and propylitic. The most important characteristics of mineralization at this deposit such as tectonic setting, host rocks, mineralogy, mineral paragenesis and alteration suggest that Gomish-tappeh show similarities with epithermal Zn-Pb-Cu (Ag) deposits.