Preliminary studies of fluid inclusions in Damoqujia gold deposit along Zhaoping fault zone,Shandong province,China

The Damoqujia gold deposit,discovered recently and located in the north of Zhaoping fault zone,is a large altered rock type 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℃and 110～150℃; corresponding to the four stages of hydrothermal ore-forming processes:coarse grain pyrite-milk white quartz stage(Ⅰ),smoky gray Au-bearing quartz-fine grain pyrite stage(Ⅱ),Au-bearing polymetallic sulfide-quartz stage(Ⅲ),and quartz-carbonate stage(Ⅳ). Ore-forming fluid is with low salinity and low density,ranging from 1.4 Wt_(NaCl)% to 13.6 Wt_(NaCl)% and from 0.48g/cm^3 to 1.03g/cm^3 respectively.The inclusions are dominated by H_2O and CO_2 in gaseous compositions,and Na^+ and K^+ in positive ions,SO_4^(2-)and Cl^- in negative ions of liquid compositions.Au-S complex is the major form for transportation of gold.The pressure varied from 260MPa to 340MPa during the formation of CO_2-bearing inclusions at the early mineralization;the fluids are rich in SO_4^(2-)and Na^+.The pressure is 26-49×10~5 Pa during the formation of the aqueous salt inclusions in late mineralization,the inclusions are rich in CI^-(F^-), Na^+.δ^(18)O_(qurrtz)is 10.64～12.68%o,and the correspondingδ^(18)O_(H_2)O andδD 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-forming fluid is magmatic hydrothermal fluid in early period,but affected by meteoric water in late.

The Damoqujia gold deposit, discovered recently and located in the north of Zhaoping fault zone, is a large altered rock type 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℃ and 110 ～ 150℃ ; corresponding to the four stages of hydrothermal ore～forming processes ： coarse grain pyrite～milk white quartz stage （ I ）, smoky gray Au～bearing quartz～fine grain pyrite stage （ 11 ） , Au～bearing polymetallic sulfide～quartz stage （ III ） , and quartz～carbonate stage （ IV ）. Ore～forming fluid is with low salinity and low density, ranging from 1.4 WtNacl% to 13.6 WtN～cl% and from 0.48g/cm～ to 1.03g/cm～ respectively. The inclusions are dominated by H20 and CO2 in gaseous compositions, and Na ＋ and K ～ in positive ions, SO～～ and CI ～ in negative ions of liquid compositions. Au～S complex is the major form for transportation of gold. The pressure varied from 260MPa to 340MPa during the formation of CO2～bearing inclusions at the early mineralization; the fluids are rich in SO～～ and Na ＂. The pressure is 26 ～49 ～ 105 Pa during the formation of the aqueous salt inclusions in late mineralization, the inclusions are rich in CI～ （ F～ ）, Na～. ～$18Oqu～,zis 10. 64 ～ 12.68%0, and the corresponding ～518 OH2o and ～＆D is -5.44 ～ 6.47%0 and -95.52 ～ 106.48%o respectively. Based on the studies about compositions and hydrogen and oxygen isotopes of inclusions, it is evidenced that ore-forming fluid is magmatic hydrothermal fluid in early period, but affected by meteoric water in late.