Ore geology, fluid inclusion, and stable isotope constraints on the origin of the Damoqujia gold deposit, Jiaodong Peninsula, China

Abstract

The Damoqujia gold deposit within the Zhaoping Fault Zone on Jiaodong Peninsula in eastern China is hosted primarily by Mesozoic granitoids and contains >60 t of gold, making it an important gold producer. Three mineralization stages are distinguished (early, middle, and late): (K-feldspar)–sericite–quartz–pyrite, quartz – gold – polymetallic sulfides, and quartz–carbonate. Gold deposition occurred mainly in the middle stage. The primary fluid inclusions of three stages are mainly homogenized at temperatures of 236–389, 191–346, and 104–251 °C, with salinities of 2.96–11.33, 1.39–17.28, and 0.53–11.48 wt.% NaCl equivalent, respectively. Fluid inclusion studies indicate that the metallogenic system evolved from CO2-rich mesothermal homogeneous fluids to CO2-poor aqueous fluids due to inputs of meteoric waters. The gold was carried as a bisulfide complex in the ore-forming fluids. Precipitation of gold was caused by a combination of fluid immiscibility and water–rock interaction. Studies of the fluid inclusion characteristics (medium temperature, CO2-rich, and low salinity H2O–CO2–NaCl homogeneous system), hydrogen and oxygen isotopes ([Formula: see text] = –1.0‰ to 7.6‰, δD = –109‰ to –77‰), sulfur values ([Formula: see text] = 4.5‰ to 8.5‰), and regional geological events show that the ore-forming fluids reservoir was likely metamorphic in origin. Based on the immiscibility of fluid inclusion assemblages, the estimated depth and pressure of trapping are 8.3–10.2 km and 83–276 MPa, respectively, corresponding to the depth and pressure of mineralization.