Ore-forming processes, O-C isotopes geochemistry, and fluid inclusions in the Darreh-Zanjir fault control MVT-type Zn-Pb deposit: Iran

The Darreh-Zanjir Zn-Pb deposit is the typical epigenetic carbonate-hosted Zn-Pb deposit in Iran. Mineralization occurs as vein fillings and irregular replacement ore bodies consisting of sphalerite and galena, and with pyrite, chalcopyrite, dolomite, barite, and minor quartz and calcite in the Lower Cretaceous carbonate host rock. Textures include breccia, replacement, massive, and vein-veinlet style. Here, we provide research of the ore geology, geochemistry, and ore-forming fluids of the Darreh-Zanjir Zn-Pb deposit. The vein replacement-shaped ore body is located close to a normal fault. The shape and size of the mineralized body suggest that epigenetic dolomites are replacements with sulfide minerals. Dolomitization is the main wall rock alteration style; alteration intensity increases toward the normal fault. Fluid inclusion microthermometry was carried out on hydrothermal dolomite associated with sulfides. Homogenization temperatures of fluid inclusions from this deposit are predominately <200 degrees C, with salinities of 6.62 to 22.67 wt.% NaCl equiv. The delta C-13(PDB) and delta O-18(SMOW) values of host limestones and hydrothermal dolomites plot the near-marine carbonate rocks field in a plot of delta C-13(PDB) vs. delta O-18(SMOW) diagram. It suggests that CO2 in the hydrothermal fluids mainly originated from marine carbonate rocks. C and O isotopes, along with fluid inclusions, textural, mineralogical, and geochemical data combined with basic features of MVT-type deposits, suggest that this deposit has formed as a result of the migration of basinal fluids coincident with tectonic activity along with ore-controlling structures. Characteristics of the Darreh-Zanjir deposit are compatible with a Mississippian Valley-type (MVT) classification.