| Zuoba tungsten deposit, which is a typical quartz vein wolframite deposit, is located in Dayu of Chongyi-Dayu-Shangyou area which is a multi-metal mineralization intensive areas of tungsten in Southern Jiangxi. It occurs mainly in metamorphic sand-shale of Aurora and Cambrian, and controlled obviously by strong tectonic and magmatism of region. In this paper, with detailed field geological survey and previous preliminary research results as the starting point, selecting fluid inclusions in Tungsten-containing quartz veins as the main research object, the author summarize systematically the mineralization feature of Zuoba tungsten deposit and tried to probe and analysis the hot issues about ore fluid nature, origin, evolution characteristics and metallogenic mechanism etc. by the various theoretical research methods of tectonics, ore deposit ore mineralogy, mineral petrology, rock geochemistry, Geochemistry of fluid inclusions etc.The fluid inclusions petrographic observations show that fluid inclusions in tungsten-containing quartz veins are well developed, the main types of fluid inclusions is gas-liquid two-phase inclusions(typeⅠ), pure liquid inclusions(typeⅡ) and pure vapor inclusions(type Ⅲ).The fluid inclusions microthermometry show that fluid inclusions homogenization temperature of Zuoba tungsten deposit vary from 143 to 447 ℃, concentrated in 180~260 ℃, can be divided into two metallogenic temperature range( 260~360 ℃, 260~160 ℃), indicating that Zuoba tungsten deposit haved experienced two stages of hydrothermal activity at least, and the temperature range of 160~260 ℃ represent probably the main mineralization stage od Zuoba tungsten deposit. The range of salinity is 1~12.8 wt%NaCleq, concentrated in 2~8 wt%NaCleq;The range of density is 0.63~0.96 g/cm3, average is 0.87 g/cm3; The range of mineralization pressure is 39.3~95.8 MPa, average is 57.79 MPa; The range of mineralization depth is 4.96~8.07 km, average is 6.08 km. These suggest that the ore-forming fluids of Zuoba tungsten deposit is a hydrothermal fluid with high and medium temperature, low salinity, low density, and the metallogenic process is in high-medium pressure and deep-medium metallogenic environment.The component analysis of gas-liquid of fluid inclusions show that the main component of liquid phase of ore-forming fluid is Na+, Ca2+, Cl- and SO42-, the main component of gas phase is water vapor, less of CO2, H2, N2 and other gases. The composition characteristics of gaseous and liquid phase of ore-forming fluid show that ore-forming fluid has multi-source mixed characteristics of magmatic hydrothermal fluid, meteoric water, hot brine and metamorphic water. The metallogenic process is in the environment with relatively weak reduction or partial oxidation.The REE and trace elements geochemical analysis of ore-forming fluid show that the ΣREE of ore-forming fluid of Zuoba tungsten deposit is low relatively, REE patterns curve overall showed nearly flat with a weak positive or negative Eu anomaly. The fractionation of LREE and HREE are not obvious. δEu= 0.05~3.29, average is 1.31, δCe=0.47~0.94, average is 0.74. The ore-forming fluid is relatively enriched W, Mo, Ni and other ore-forming elements, and the ratios of Mo/W, Ga/Tl and Y/Ho have larger changes, showing the complicated metallogenic process of Zuoba tungsten deposit, and metallogenic process is possibly always in relative oxidation environment, and ore-forming fluid is mixed by metamorphic water or meteoric water.Comprehensive analysis, the ore-forming fluid of Zuoba tungsten deposit is main magmatic hydrothermal early, and continuously mixed by meteoric water and metamorphic water in late period. The mixing of different nature of fluids may be the main mechanism of accelerating the precipitation and enrichment of tungsten in deposit.There are similar characteristics of ore-forming fluid between Zuoba tungsten deposit and some quartz vein wolframite deposits of Southern Jiangxi and foreign. They are generally showing high-medium temperature, low salinity, low density characteristic of ore forming fluids and high-medium pressure, deep-medium metallogenic environment. It is worth noting that there are similar metallogenic environment, and nature, source and evolution characteristics of ore-forming fluid between Zuoba tungsten deposit and Maoping tungsten deposit, may be indicative of rock type tungsten metallogenic potential in deep of Zuoba tungsten deposit. |
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