CHARACTERISTICS AND SIGNIFICANCE OF THE FLUID INCLUSIONS IN QUARTZ VEINS TYPE ORE BODIES FROM SHIMENSI TUNGSTEN DEPOSIT, NORTHERN JIANGXI
The Shimensi tungsten polymetallic deposit,a recently discovered superlarge deposit in northern Jiangxi,Province.It may break the traditional pattern of "tungsten in the south and copper in the north" of Jiangxi province.To reveal the characters and evolutions of the ore-forming fluids,the fluid inclusions in quartz vein ore bodies were investigated by using microthermometry and the Raman microprobe.On the basis of microscopic investigation,the fluid inclusions are mainly composed of liquid-rich aqueous inclusion and a few liquid-pure,gas-pure,gas-rich and three phase containing CO2 inclusions.Microthermometry results show that the homogenization temperature is between 147.1 ℃ and 316.2 ℃,concentrating on 201.5 ℃ to 259.2 ℃,average value of 211.1 ℃.The salinity is between the range of from 0.88％ to 7.31％ NaCleq,an concentrating on 1.05％～3.06％ NaCleq,an average value of 2.45％ NaCleq.The density is within the limits of from 0.79 g/cm3 to 0.94 g/cm3,concentrating on 0.82 g/cm3 ～0.92 g/cm3,an average value of 0.87 g/cm3.The raman microprobe analysis results that CH4,CO2 and N2 are detected.The results plot indicate that the ore-forming fluids have the main composition of the medium temperature,low salinity and low density NaCl-H2 O-CH4 + (CO2,N2) system.During the evolution of the ore-forming fluid,the mixing of magmatic hydrothermal fluid and meteoric water,and the boiling effect of fluid.The combination of the mixing and boiling are the main factor that causes the Precipitation of tungsten compound and break the chemical equilibrium.enthalpy-salinity plot indicate that mixing appears as the most dominating process,local boiling occurred during the evolution of the hydrothermal system.
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