Two sericite samples associated with the main ore-stage pyrites from pyritic phyllic ores of the deposit with weighted mean plateau 40Ar/39Ar age of 120.7 +/- 0.6 Ma and 119.2 +/- 0.5 Ma, respectively, were selected for 40Ar/39Ar geochronology. On the basis of petrography and microthermometry, three types of primary fluid inclusions related to the ore forming event were identified: type 1 H2O-CO2-NaCI, type 2 aqueous, and type 3 CO2 fluid inclusions (in decreasing abundance). Stage I quartz contains all three primary fluid inclusions, while stages 2 and 3 quartz contain both type 1 and 2 inclusions, and stage 4 quartz contains only type 2 inclusions. The contemporaneous trapping, similar salinities and total homogenization temperature ranges, and different homogenization phases of type 1 and type 2 inclusions indicate that fluid immiscibility did take place in stages I, 2 and 3 ores, with P-T conditions of 190 to 85 MPa and 334 to 300 degrees C for stage 1 and 200 to 40 MPa and 288 to 230 degrees C for stages 2 and 3. Combined with the H-O-C-S-Pb isotopic compositions, ore-forming fluids may have a metamorphic-dominant mixed source, which could be associated with the dehydration and decarbonisation of a subducting paleo-Pacific plate and characterized by medium-high temperature (285350 degrees C), CO2-bearing (similar to 8 mol%) with minor CH4 (1-4% in carbonic phase), and low salinity (3.38-8.45 eq. wt.% NaCI). During mineralization, the fluid finally evolved into a medium-low temperature NaCI-H2O system. Au(HS)(2)(-) was the most probable gold-transporting complex at Wang'ershan, due to the low temperature (157-350 degrees C) and near-neutral to weakly acidic ore fluids. The reaction between gold-bearing fluids and iron bearing wall-rocks, and fluid-immiscibility processes caused via fluid-pressure cycling during seismic movement along fault zones that host lode-gold orebodies, which led to breakdown of Au(HS)(2)(-), are interpreted as the two main precipitation mechanisms of gold deposition. Two sericite samples associated with the main ore-stage pyrites from pyritic phyllic ores of the deposit with weighted mean plateau 40Ar/39Ar age of 120.7 +/- 0.6 Ma and 119.2 +/- 0.5 Ma, respectively, were selected for 40Ar/39Ar geochronology. On the basis of petrography and microthermometry, three types of primary fluid inclusions related to the ore forming event were identified: type 1 H2O-CO2-NaCI, type 2 aqueous, and type 3 CO2 fluid inclusions (in decreasing abundance). Stage I quartz contains all three primary fluid inclusions, while stages 2 and 3 quartz contain both type 1 and 2 inclusions, and stage 4 quartz contains only type 2 inclusions. The contemporaneous trapping, similar salinities and total homogenization temperature ranges, and different homogenization phases of type 1 and type 2 inclusions indicate that fluid immiscibility did take place in stages I, 2 and 3 ores, with P-T conditions of 190 to 85 MPa and 334 to 300 degrees C for stage 1 and 200 to 40 MPa and 288 to 230 degrees C for stages 2 and 3. Combined with the H-O-C-S-Pb isotopic compositions, ore-forming fluids may have a metamorphic-dominant mixed source, which could be associated with the dehydration and decarbonisation of a subducting paleo-Pacific plate and characterized by medium-high temperature (285350 degrees C), CO2-bearing (similar to 8 mol%) with minor CH4 (1-4% in carbonic phase), and low salinity (3.38-8.45 eq. wt.% NaCI). During mineralization, the fluid finally evolved into a medium-low temperature NaCI-H2O system. Au(HS)(2)(-) was the most probable gold-transporting complex at Wang'ershan, due to the low temperature (157-350 degrees C) and near-neutral to weakly acidic ore fluids. The reaction between gold-bearing fluids and iron bearing wall-rocks, and fluid-immiscibility processes caused via fluid-pressure cycling during seismic movement along fault zones that host lode-gold orebodies, which led to breakdown of Au(HS)(2)(-), are interpreted as the two main precipitation mechanisms of gold deposition. Two sericite samples associated with the main ore-stage pyrites from pyritic phyllic ores of the deposit with weighted mean plateau 40Ar/39Ar age of 120.7 +/- 0.6 Ma and 119.2 +/- 0.5 Ma, respectively, were selected for 40Ar/39Ar geochronology. On the basis of petrography and microthermometry, three types of primary fluid inclusions related to the ore forming event were identified: type 1 H2O-CO2-NaCI, type 2 aqueous, and type 3 CO2 fluid inclusions (in decreasing abundance). Stage I quartz contains all three primary fluid inclusions, while stages 2 and 3 quartz contain both type 1 and 2 inclusions, and stage 4 quartz contains only type 2 inclusions. The contemporaneous trapping, similar salinities and total homogenization temperature ranges, and different homogenization phases of type 1 and type 2 inclusions indicate that fluid immiscibility did take place in stages I, 2 and 3 ores, with P-T conditions of 190 to 85 MPa and 334 to 300 degrees C for stage 1 and 200 to 40 MPa and 288 to 230 degrees C for stages 2 and 3. Combined with the H-O-C-S-Pb isotopic compositions, ore-forming fluids may have a metamorphic-dominant mixed source, which could be associated with the dehydration and decarbonisation of a subducting paleo-Pacific plate and characterized by medium-high temperature (285350 degrees C), CO2-bearing (similar to 8 mol%) with minor CH4 (1-4% in carbonic phase), and low salinity (3.38-8.45 eq. wt.% NaCI). During mineralization, the fluid finally evolved into a medium-low temperature NaCI-H2O system. Au(HS)(2)(-) was the most probable gold-transporting complex at Wang'ershan, due to the low temperature (157-350 degrees C) and near-neutral to weakly acidic ore fluids. The reaction between gold-bearing fluids and iron bearing wall-rocks, and fluid-immiscibility processes caused via fluid-pressure cycling during seismic movement along fault zones that host lode-gold orebodies, which led to breakdown of Au(HS)(2)(-), are interpreted as the two main precipitation mechanisms of gold deposition.
