Fluid inclusion study of Xihuashan tungsten deposit in the southern Jiangxi province,China |
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| Authors: | G Giuliani Y D Li T F Sheng |
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| Institution: | (1) ORSTOM, Embaixada da França, CP 665, 70404 Brasilia DF, Brazil;(2) Jiangxi Bureau of Geology, Nanchang, Jiangxi, China;(3) Institute of Mineral Deposits, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, Beijing, China |
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| Abstract: | The Xihuashan tungsten deposit is closely related to a small highly evolved granitic intrusion. The fluid phases associated with the wolframite-bearing quartz veins have been investigated using microthermometry and the Raman microprobe; they are highly variable in density and composition. The earlier fluids are low-density and low-salinity CO2-bearing aqueous solutions circulating at temperatures up to 420 °C, and low-salinity (2–3 equiv. wt% NaCl) aqueous solutions without traces of CO2 circulating at high temperatures 280°–400 °C) involved in a specific hydrothermal fracturing event; limited unmixing occurs at 380 °C and 200–100 bar in response to a sudden pressure drop. The second types of fluids related to deposition of idiomorphic drusy quartz are typical CO2-bearing aqueous solutions with low salinity (2.5 equiv. wt% NaCl) homogenizing at low to moderate temperatures (180°–340 °C). The late fluids characterize the sulfide deposition stage; they are aqueous fluids with variable salinities homogenizing in the liquid phase between 100° and 275 °C. The Xihuashan hydrothermal evolution resulted from a discontinuous sequence of specific events occurring between 420° and 150 °C and during a continuous hydrothermal evolution of the system during cooling. The role played by the CO2-rich fluids in the transport and deposition of tungsten in the hydrothermal environment is discussed. |
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