Manto-type copper mineralization in the central part of the Urumieh-Dokhtar magmatic arc (Qom-Saveh region) with emphasis on the East Narbaghi deposit, northeast Saveh

The Manto-type copper deposits of the Qom-Saveh region are located in the central part of the Urumieh-Dokhtar magmatic arc and occurred in the Eocene volcano-sedimentary sequence. The most important deposits in the studied area are East Narbaghi, Khankishi, Veshnaveh, and Kahak. The geometry of mineralization is stratabound and hosted in the silty tuff, tuff breccia, andesite, lithic crystal tuff, and amygdaloidal andesite basalt. The hypogene ore minerals include chalcocite, bornite, and minor chalcopyrite with vein-veinlet, open space filling, disseminated, and replacement textures. Based on geological studies, two major stages are distinguished for hypogene mineralization. Disseminated and framboidal pyrite formed during the first stage of mineralization which occurred simultaneously with volcanism, sedimentation, and early diagenesis. The second stage of mineralization took place during late diagenesis when copper-bearing oxidized fluids entered into the reduced pyrite-bearing host rock, causing the replacement of the first stage pyrites by copper sulfides. The sulfur isotope composition of sulfide minerals from the East Narbaghi deposit varying from -10.2 to -4.4 ‰ (averaging -6.7 ‰VCDT) indicates the presence of a reduced environment resulting from activation of sulfate-reducing bacteria. The geology, ore mineralogy, alteration characteristics, and sulfur isotopic compositions suggest that the studied ore deposits may be classified as Manto-type mineralization.