Preliminary studies of fluid inclusions in Damoqujia gold deposit along Zhaoping fault zone,Shandong province, China
摘要
The Damoqujia gold deposit, discovered recently and located in the north of Zhaoping fault zone, is a large altered rocktype deposit. In this paper, we report the preliminary research results of the fluid inclusions and discuss its metallogenic implications.The homogenization temperatures of fluid inclusions fall into four ranges: 310~350℃,230~270℃,160~200℃ and110~150℃;corresponding to the four stages of hydrothermal ore-forming processes: coarse grain pyrite-milk white quartz stage (Ⅰ),smoky grayAu-bearing quartz-fine grain pyrite stage (Ⅱ),Au-bearing polymetallic sulfide-quLutz stage (Ⅲ),and quartz-carbonate stage (Ⅳ).Ore-forming fluid is with low salinity and low density, ranging from 1.4 WtNaCl%to 13.6WtNaCl% and from 0.48g/cm3 to1.03g/cm3respectively. The inclusions are dominated by H2O and CO2 in gaseous compositions, and Na+ and K+in positive ions, SO24-and Cl-in negative ions of liquid compositions. Au-S complex is the major form for transportation of gold. The pressure varied from 260MPa to340MPa during the formation of CO**2-bearing inclusions at the early mineralization;the fluids are rich in SO24-and Na+. The pressureis 26-49r105 Pa during the formation of the aqueous salt inclusions in late mineralization, the inclusions are rich in Cl-(F-),Na+.δ18Oqurrtz is 10.64~12.68‰,and the corresponding δ18 OH2O and δD is -5.44~6.47‰and-95.52~-106.48‰。respectively. Based on the studies about compositions and hydrogen and oxygen isotopes of inclusions, it is evidenced that ore-formingfluid is magmatic hydrothermal fluid in early period, but affected by meteoric water in late.