Mineralization, geochemistry, fluid inclusion and stable isotopes (O, S) studies in the Takht Fe-skarn deposit, NE Hamedan

The Takht iron deposit is located 120 km northeast of the Hamedan City in the Urumieh-Dokhtar magmatic belt. The Miocene Takht granodiorite intruded into the Cretaceous carbonates and resulted in Fe-skarn formation. Epigenetic mineralization in the Takht Deposit occurred predominantly as vein and lenticular ore bodies accompanied with argillic, carbonation, chloritization, epidotization and silicfication alterations and minerals including garnet, pyroxene, epidote, tremolite- actinolite, phlogopite, hornblende, quartz, calcite, magnetite, pyrite, specularite, chalcopyrite, hematite, limonite, goethite and malachite. Chemical composition indicates the presence of Si, Al, Ca, Mg, Ti and chalcophile elements such as Cu, Zn, As and Pb that originate from the coexistence of silicate and sulfide minerals with magnetite. The microthermometric results revealed homogenization temperatures (Th) from 153.2°C to 338.3°C and salinity from 0.827 wt.% NaCl eq. to 25.36 wt.% NaCl eq.. The δ18O (SMOW) values of magnetite were measured in the range of −0.46‰ to .31‰ and δ18O water is .1‰ to .9‰, respectively. These isotope values are similar to magmatic fluids that were also equilibrated with 18O enriched sources. The δ34S (V-CDT) values of pyrite show ranges of .3‰ to .5‰ and the original fluid δ34S H2S values were estimated ranging from .7‰ to .9‰. These positive δ34S values confirm that sulfur is provided by evaporate sulfates. During the retrograde stage of the Takht Skarn, re-mobilized metals accompanied with metal-bearing fluids (provided by intrusion) were mixed with sulfur-bearing descending meteoric waters and eventually, the mixing of the two fluids led to calcic Fe-skarn mineralization in Cretaceous carbonates.