CHARACTERISTICS AND SIGNIFICANCE OF THE FLUID INCLUSIONS FROM YAOGANGXIAN TUNGSTEN DEPOSIT IN SOUTH OF HUNAN

Abstract

There are three dominant types of fluid inclusion related to metallogensis in Yaogangxian quartz-vein wolframite deposit and skarn scheelite deposit: liquid-rich inclusion, gas-rich two-phase inclusion and daughter-minerals bearing polyphase inclusion. The homogenized temperatures and salinity of fluid inclusions in quartz range from 180°C to 300°C and from 0.88 to 6.45 wt% NaCl eqv, of the inclusions in garnet vary from 190°C to 300°C and from 0.1 to 8.95 wt% NaCl eqv respectively. Density of the fluids is 0.81-0.89g/cm3. These features represent that the fluids are medium temperature, low density and low salinity in the two types of fluids in this tungsten deposits. Pressure of the fluid was 120-16OMPa, indicating that the two types of tungsten deposits were formed at depth of 7-9km. The analytic results get by Laser Laman Spectroscopy, indicate that the fluid is rich in volatile components, such as CH4, CO2 and H20. Therefore, from the formation of the skarn scheelite to the quartz-vein, the fluid is the transitional fluid between magma and hydrothermal. Since Yanshanian Period, this area suffered asthenosphere upwelling, lithospheric extension, thinning and crust-mantle interaction, so the fluid riched in C-H of W-bearing quartz vein of Yaogangxian tungsten deposit most likely came from mantle transition belt or asthenosphere.