Abstract:

The Datuanshan copper (molybdenum) deposit is a typical magmatic-hydrothermal superimposing copper (molybdenum)
deposit at the Shizishan orefield in Tongling, Anhui Province. This deposit is intimately associated with the Early Cretaceous
Datuanshan quartz monzodiorite. Based on thorough petrographic observations of the ore-bearing quartz at the sulfide mineralization
stage, we have identified plenty of primary fluid inclusion assemblages that are well preserved. Three types of primary fluid inclusions
are described as vapor (Type I), aqueous (TypeⅡ), and daughter-mineral bearing multiphase inclusions (Type III). Statistical analysis of
all the measured filling temperatures of the fluid inclusions shows two significant peaks at 375~405℃ and 285~315℃. The statistic peak
for salinities appears in the range from 5.0 wt.% to 10.0 wt.% NaCl eq. Raman analyses reveal that water vapor is the dominant
component in the gaseous phase, occasionally with small amount of CO2 and CH4. Hydrogen and oxygen isotopic compositions are
characterized by magmatic water. These results suggest that the ore-forming fluids at the Datuanshan deposit were mainly derived from
magmatic water. The fluids experienced multi-episodes of boiling, and were trapped from heterogenize fluid systems. Combining with
results from previous relevant studies in literature, we conclude that the magmatic-hydrothermal fluids at the Shizishan orefield share
common chemical properties, and experience similar physical chemical conditions. The multi-episode fluid boiling processes have
probably played a key role in metal re-distribution, transport，and precipitation.

Key words: fluid inclusions, microthermometry, Raman, Hydrogen, Oxygen isotopes, Datuanshan Cu (Mo) deposit, Shizishan orefield