Stable isotope evidence for the genesis of Zn-Pb sulfide mineralization in the Kuh-e-Surmeh deposit

The Kuh-e-Surmeh Pb-Zn deposit is located 50 km south of Firouzabad in the Zagrous mountain folding belt. The upper Permian carbonates of lower Dalan Formation are hosted by mineralization. Galena، sphalerite and pyrite are the main ore minerals and chalcopyrite and smithsonite have been found as the accessory minerals. Mineralogical paragenesis point to mineralization taken place in several stages. Based on the stable isotope analyses the δ34S values of the sulfide minerals are in the range of +10. 12 to +15. 2‰ and those of the sulfate minerals vary between +12. 8 to +14. 9 ‰. The δ18O and δ13C values of the white dolomites exhibit values in the range of -11. 29 to -18. 32‰ and -6. 08 to -8. 31‰ for δ18OPDB and δ13CPDB respectively. Geochemical evidences imply that thermochemical sulfate reduction processes have supplied required reduced sulfur for ore deposition، which seems to be provided through sulfates reduction in the Jahani salt dome. So the Kuh-e-Surmeh mineralization could be explained by mixing model. Dolomitization is affected by two different fluids. The main fluid originated from deeper hydrothermal or basinal sources related to the Precambrian rock units. These brine fluids have ascended through faults related salt diapirism. The second one is sourced from meteoric water. Comparing of sulfur isotope values of the Kuh-e-Surmeh deposit with other carbonate hosted base metal sulfides deposits، display that the mineralization is likely the Mississippi valley type.