The origin of ore-forming fluids in the Mahour polymetal ore deposit, using electron microprobe data and sulfur isotopes (East of Lut block, Central Iran)

The Mahour polymetal deposit, located east of the Lut block, is a three-km-long and 0.5-2m wide vein formed in hypabyssal acid rocks. Downward, three leached zones (malachite, azurite, hematite, goethite and atacamite), supergene (bornite, covellite, chalcocite, anglesite, greenockite and hawleyite), and hypogene (magnetite, chalcopyrite, pyrite, galena and sphalerite) are observed in the deposit. The results of electron microprobe analyses show the presence of varying amounts of Ag, As, Sb, In, Cd, Zn, Fe and Cu, in the sulfide minerals of Mahour deposit. Three rare mineral phases, namely atacamite, greenockite and hawleyite in the leached and supergene zones, were identified by the electron microprobe analyses. The types of alteration present in the deposit are silicic, sericitic, propylitic, argillic, and potassic. The 34SCDT values for eight sulfide samples (pyrite, chalcopyrite, galena, sphalerite and bornite) in Mahour deposit vary between 0.2 to 4.07%, with a mean value of 2.96%. Inferred temperature from thermometric calculations, based on the sulfur isotope compositions of sulfide pairs in equilibrium, indicate temperatures of 215-380 ºC. Therefore, it is concluded that sulfur needed for the generation of sulfide minerals in the Mahour polymetal deposit was supplied by either ore-forming fluids or igneous rocks in the region.