REE and microthermometric analyses of fluid inclusions in the Jinding Pb-Zn deposit show that homogenization temperature of ore-forming fluid is at 54℃~309℃ and 143℃ in average,and its salinity(ω(NaCl)) is at 1.6%~18.0% and 6.0% in average.
Based on the characteristics of fluid inclusions and their composition, We deduce that as component part of the ore-forming fluid, the CO2 - CH4 -H2O system is possibly a special ore-forming fluid.
The pH of ore forming fluid is 6.7~7.2, and Eh -0.69~-0.73. From these data, it can be concluded that the characters of ore forming fluid are mid low temperature, low salinity, rich H 2O, CO 2, HCO -, Ca 2+ , K +, Na +, and Cl -, middle pH and weak reduction.
The ore-forming fluids of Yanshanian magmatism evolved from high temperature,high salinity and K-rich fluids via moderate-high temperature and CO2(CH4)rich fluids to moderate-low temperature and low salinity fluids.
The analytical results suggest that the dominant volatiles in the ore-forming fluids are H2O,CO2 and CH4,with minor C2H6,H2S,N2 etc. Na+,K+ as well as Ca2+,Mg2+ are dominant cations whereas Cl-and SO42-are major anions. High K and CO2(CH4)constitute the main feature of the ore-forming fluids related to Yanshanian magmatism.
While inclusion study indicates that the ore fluid comes from dynamic metamorphic water source with a little influence of magmatic and meteoric water. The ore fluid is featured by density of 0.791~0.971 g/cm 3 and salinity of 2.36%~5.5%. The gold deposit forms at 1.61~2.68 km below the surface with a temperature of 198~290℃ and pressure of 42~70 MPa.
The ore fluid flowed from the basin to the platform between the basin and the platform and migrated from the inter-platform basin to the isolated platform in the Youjiang Basin.
Theδ18O andδD values of the fluid vary from -2.7‰- +4.4‰ and -50‰--87‰ Evidence developed from fluid inclusions and geological setting indicates that the ore fluid was a mixture of magmatic and meteoric-hydrothermal waters.