Disseminated, veinlet and vein Pb-Zn, Cu and Sb polymetallic mineralization in the GaleChah-Shurab mining district, Iranian East Magmatic Assemblage (IEMA)
Authors: Behzad Mehrabi; Ebrahim Tale Fazel; Ali Nokhbatolfoghahai
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The Iranian East Magmatic Assemblage (IEMA) in the Central Lut region, hosted porphyry and vein-type polymetallic mineralization. The GaleChah-Shurab mining district is located in NW of the IEMA. Volcanic and subvolcanic bodies in the area are composed of calc-alkaline porphyry quartz-latite, porphyry dacite and rhyodacite and hornblende-biotite andesite, equivalent to I-type granite. They emplaced in Tertiary and intruded the Jurassic shale, siltstone and limestone basement (Shemshak Fm). The faults, joints and fractures, are the main controls on the mineralization, in forms of disseminated, vein, veinlet and minor stockwork and brecciation type mineralization of Pb, Zn, Cu, Sb and trace elements. Vein and veinlet of Pb+Zn±Cu±Sb in the Gale-Chah abandoned mine accompanied by carbonate and silicic alterations in association with galena, sphalerite, pyrite, chalcopyrite, bournonite and tetrahedrite as the hypogene ore minerals and their supergene products including cerussite, covellite, digenite and second-generation colloidal pyrite. The Pb+Zn+Cu+Sb mineralization associated with sericitic and silicic alterations in the Shurab abandoned mine, is composed of two types of mineralization, veinlet and brecciation vein in the porphyry dacite boundaries with Jurassic shale and sandstones, and the disseminated and disseminated-veinlet mineralization which is hosted by the altered porphyry dacite and rhyodacite intrusive rocks. The mineral assemblages are galena, sphalerite, stibnite, As-bearing pyrite, chalcopyrite and tetrahedrite-tennantite complex hypogene-sulfide ore as a hypogene ore, and malachite, covellite, cerussite and melancoitic pyrite as a sulfide-oxide supergene ore. The Pb+Zn+Sb±As±Ag polymetallic occurrence is associated with sericitic, carbonate and chloritic alteration assemblage in the Chupan occurrence, in two forms, I) vein, veinlet-stockwork (30m depth) confined to fault structures and II) disseminated-replacement (below 70m) mainly hosted in rhyodacite and porphyry dacite rocks. The hypogene minerals are galena, sphalerite, stibnite, pyrite, realgar-orpiment, arsenopyrite, and chalcopyrite with extensive occurrence of oxide-sulfide supergene products, such as Mn-oxide, hematite, malachite and colloidal pyrite. Fluid inclusion study show that disseminated veinlet Cu and disseminated-replacement polymetallic mineralization at the Shurab and Chupan deposits, respectively occurred in the high temperature, salinity and depth compared to vein-veinlet Pb and Zn mineralization of Gale-chah deposit. It seems that the mineralization is related to hydrothermal fluid evolution affected by mixing with cold and low salinity meteoric water.