Mineralogical evolutions of carbonate-hosted Zn-Pb-(F-Mo) deposits in Kuhbanan-Bahabad area, Central Iran: metal source approach



Over forty nonsulfide dominated Zn (-Pb) deposits with the same character are situated at the Kuhbanan-Bahabad area (KBA), Central Iran. The host rock of these deposits is the Upper Permian (-Lower Triassic) carbonate rocks. Mineralogical studies showed that three dependent mineralization have been occurred in the area. Firstly, a unique and less common disseminated sulfide (sphalerite, galena and pyrite) have formed during the diagenesis stages in the Upper Permian carbonate rocks as a syndiagenetic mineralization. Secondly, because of the later tectonic squeezing of the sulfide bearing strata of Upper Permian, the economic vein-type sulfide mineralization has formed hydrothermally and is present in a few deposits of the area (Tajkuh and Tarz deposits). Sphalerite, galena and pyrite are the main sulfide minerals and a lesser amounts of chalcopyrite and arsenopyrite is accompanied the ore. Sulfur stable isotope studies on the main sulfide minerals showed that the mineralization is comparable with the MVT deposits and the mixing model is the best model for sulfide precipitation. Finally, the third mineralization evolution is outcropping the vein-type sulfide mineralization and exposing to the oxidation conditions and so, formation of the nonsulfide Zn (-Pb) ore has occurred. Smithsonite, hydrozincite and hemimorphite are the most abundant nonsulfide minerals and some minor to accessory minerals such as cerussite, anglesite, willemite and wulfenite are present in some cases.  Carbon and oxygen stable isotope studies showed that combination of meteoric, ground and entrapped connate waters are the fluids responsible for transformation of sulfide to nonsulfide minerals. It seems that the Upper Permian carbonate rocks have played two separate important roles, source and host rock for the mineralization in the KBA.