Mineralization and structural features of Kalchouyeh copper-gold deposit (west-central Iran)

Abstract

The Kalchouyeh copper deposit is located about 110 km east of Isfahan, in the Urumieh-Dokhtar magmatic assemblage (UDMA) arc of Iran. Mineralization is closely associated with the calc-alkaline volcanism of the UDMA arc and controlled by northwest–southeast trending strike-slip faults (Qom-Zefreh and Nain-Baft faults). A pull-apart basin along these strike-slip faults has facilitated the localization of magma and related hydrothermal systems and eventually the development of Kalchouyeh mineralization. Copper mineralization occurs mainly as veins and veinlets and is related to two distinct main stages of hypogene and supergene. Hypogene mineralization includes Cu and Pb sulfides (chalcopyrite, pyrite, galena) and Fe oxide (magnetite). Chalcocite and covellite are found in supergene mineralization. Microthermometric measurements of fluid inclusions on two mineralized veins show the presence of two different kinds of ore fluids: (1) low temperature and salinity in relation to vein A (homogenization temperature 175–252 °C, salinity 0.82–4.23 wt.% NaCl) and (2) low to moderate temperature and salinity in relation to vein B (homogenization temperature 255–324 °C, salinity 0.16–9.32 wt.% NaCl). Copper mineralization at Kalchouyeh appears to be epithermal and low-sulfidation in style, and ore deposition was the result of cooling and surface fluid dilution.