Origin and evolution of ore-forming fluids, and genesis of the Duhuangling and Jiusangou gold deposits in eastern Yanbian, northeast China

The Duhuangling and Jiusangou gold deposits are located east of the Yanbian area, northeast China. We present the results of systematic studies of the ore geology, fluid inclusion (FI) features, and isotopic geochemistry of the two gold deposits. Four mineralization stages have been defined in each gold deposit: pyrite + sericite + quartz (stage I), quartz + pyrite +/- chalcopyrite +/- arsenopyrite (stage II), quartz + native gold + polymetallic sulfide (stage III), and quartz-calcite (stage IV). FIs from the two gold deposits are similar and contain five types: pure vapor phase (V-type), vapor-rich phase (RV-type), liquid-rich phase (RL-type), daughter mineral-bearing polyphase (S-type), and pure liquid phase (L-type). Stage I FIs homogenize at temperatures of 350-450 C-omicron, yielding salinities of 5.40-48.67 wt.%. FIs from both stages II and III samples homogenize at 160-350 C-omicron, yielding salinities of 5.71-39.75 wt.%. FIs in pyrite from the stage II have He-3/He-4 ratios of 0.0069-0.0148 Ra and Ar-40/Ar-36 ratios of 1302-4433, demonstrating that ore-forming fluids of the two gold deposits were derived from the crust. The delta D values of the two gold deposits range from -107% to -92%, with delta O-18(H20) values from 4.3% to 9.0%, indicating that the ore-forming fluids were mainly magmatic water in origin. Lead isotope data suggest that the ore-forming materials were originated from deep crust. Integrated data indicate that both Duhuangling and Jiusangou gold deposits are medium-to high-temperature, hydrothermal gold deposits.