Characteristics of ore-forming fluids and ore genesis in the Shicheng gold deposit, Jiaodong Peninsula of eastern China

Shicheng gold deposit, located in the Muping-Rushan gold belt of Jiaodong Peninsula, is a typical polymetallic sulphide gold deposit. Fluid inclusions studies show that three stages of inclusions which CO2-rich inclusions formed at the first stage, H2O and CO2-bearing inclusions formed at the second stage and only H2O inclusions formed in the third stage can be identified. The homogenization temperatures and salinities ranging from 256 degrees C to 360 degrees C and 3. 7% NaCl to 6. 9% NaCl for the first stage represent the character of the ore-forming fluid in the early time, 168 degrees C to 270 degrees C and 4. 49% NaCl to 10. 24% NaCl for the second stage represent the property of the main ore-forming fluid, and 123 degrees C to 178 degrees C and 0. 4% NaCl to 7. 6% NaCl for the third stage reflect the property of the ore-forming fluid in the late time. Hydrogen and oxygen stable isotopes indicate that the main ore-forming fluid of the Shicheng gold deposit is the result of mixing between magmatic fluid and meteoric water, while carbon stable isotopes imply that CO2-rich mantle fluid was involved in the ore forming process, and sulfur stable isotopes further reveal that the aurum came from the source induced by mantle-crust interaction. The appearance of Shicheng gold deposit indicates that at least two mineralization events exist in the research area. The earlier one characterized by pyrite-quartz ore happened at the age of about 120Ma and the later one characterized by polymetallic sulphide ore occurred younger than 111Ma.