Fluid inclusion and O–H–C isotopic constraints on the origin and evolution of ore-forming fluids of the Cenozoic volcanic-hosted Kuh-Pang copper deposit, Central Iran

Abstract The Kuh-Pang copper deposit (2.8 Mt @ 1.65% Cu, 0.52 g/t Au, 34 g/t Ag) is a volcanic-hosted epithermal deposit in the central part of the Late Eocene-Oligocene Urmia-Dokhtar Magmatic Arc of Iran. Three stages of fluid evolution are identified at the Kuh-Pang deposit: (i) early pre-ore stage: with homogenization temperature of 205–372 °C (298 ± 45 °C), salinity of 11.3 ± 2.9 wt% NaCl equiv., fluid trapped at ∼200 bars, (ii) main-ore stage: with homogenization temperature of 175–310 °C (253 ± 43 °C), salinity of 2.1–12.5 wt% NaCl equiv. at ∼150 bars, and (iii) late post-ore stage: with homogenization temperatures of 148 to 231 °C (199 ± 24 °C), and salinity of 1.1–9.8 wt% NaCl equiv. These data record an evolution of mineral precipitation from deeper (>2 km) to shallower environments ( 18 O fluid values of +5.7 to +5.9‰ and +3.2 to +3.8‰, and δD fluid values of  −77 to −41‰ and −84 to −60‰, respectively. These data indicate a major magmatic fluid source, with slightly increasing mixing of meteoric waters. Calcite in the late post-ore stage has δ 13 C V–PDB values of −5.8 to −5.6‰ and δ 18 O V–SMOW values of 8.2–8.6‰, with calculated δ 18 O fluid and δ 13 C fluid values of −1.0 to −1.4‰ and −5.4 to −5.2‰ respectively, that are also consistent with a predominantly magmatic carbon source and a significant fluid mixing by meteoric waters.