The ilvaite-bearing skarn associations in the Galinge skarn deposit were studied to determine their physicochemical formation conditions.A thermodynamic model setting pressure of 50 MPa(Pf=Ps=50 MPa)was set up to trac...The ilvaite-bearing skarn associations in the Galinge skarn deposit were studied to determine their physicochemical formation conditions.A thermodynamic model setting pressure of 50 MPa(Pf=Ps=50 MPa)was set up to trace the skarn evolution.Petrographic evidence for replacement of garnet and magnetite by ilvaite in the early retrograde stage(Stage I)combined with thermodynamic modeling suggests that the alteration may have occurred at 400470°C under moderately high fO withΔlgfO(HM)ranges from 4 to 4.2.The model is based on a maximum 22 pressure of 50 MPa calculated from magmatic amphibole geobarometer.The continuous breakdown of ilvaite with quartz to form ferro-actinolite and magnetite occur in the late retrograde stage(Stage II).The reactions occurred at 400440°C under moderate fO(ΔlgfO(HM):4 to 4.4).In Stage III,the breakdown of ilvaite to form calcite,pyrite 22 and ferroactinolite depends on XCO which can be estimated to be in a range of 0.005 to 0.05,and the reaction would 2 occur at higher temperatures with increasing XCO.Under these conditions,the breakdown occurs at 270350°C and 2 low fO(ΔlgfO(HM):up to 5.2).The thermodynamic model for continuous evolution from Stage I to Stage III 22 completely records the conditions of the retrograde alteration,which is inconsistent with the thermobarometry imprints of fluid inclusions.Therefore,the petrography and phase relations of ilvaite are useful indicators of reaction conditions in various skarn deposit types.展开更多
Shangzhuang gold deposit located in the Wangershan fault zone of northwestern Jiaodong is of meso- hypogenic altered rock type. The ore bodies occur at the hanging wall and footwall of Wangershan fault in vein or irre...Shangzhuang gold deposit located in the Wangershan fault zone of northwestern Jiaodong is of meso- hypogenic altered rock type. The ore bodies occur at the hanging wall and footwall of Wangershan fault in vein or irregular shapes with the NE strike, NW trend, 30° -60°~ in dip and the lateral trending of SW. The ores are composed of pyrite, quartz, sericite, bismuthinite, native gold, bismuth sulfosah minerals, chalcopyrite, etc. , shown as brecciated structure and vein structure with metasomatic dissolution textures. The wall rock altera- tion is mainly described as phyllic alteration and silicification. The mineralization of this deposit is controlled by structure and altered rocks. The ore-controlling fault structures of this deposit is Wangershan fault, of which the intersection of major fault and secondary fault is the main ore-bearing position of this gold deposit, and the lar- ger arc curved position is a favorable part for ore body occurrence. On the plane, the ore body is shown as equi- distant pinch-out reproduction.展开更多
基金Projects(41172076,41802080)supported by the National Natural Science Foundation of ChinaProject(1212011085528)supported by Geological Survey Program from the China Geological Survey+3 种基金Project(2019CX035)supported by Innovation-driven Plan of Central South University,ChinaProject(201411025)supported by the Scientific Research Fund from Ministry of Land and Re-sources,ChinaProject(201309)supported by the Program of High-level Geological Talents,ChinaProject(201112)supported by the Youth Geological Talents of the China Geological Survey
文摘The ilvaite-bearing skarn associations in the Galinge skarn deposit were studied to determine their physicochemical formation conditions.A thermodynamic model setting pressure of 50 MPa(Pf=Ps=50 MPa)was set up to trace the skarn evolution.Petrographic evidence for replacement of garnet and magnetite by ilvaite in the early retrograde stage(Stage I)combined with thermodynamic modeling suggests that the alteration may have occurred at 400470°C under moderately high fO withΔlgfO(HM)ranges from 4 to 4.2.The model is based on a maximum 22 pressure of 50 MPa calculated from magmatic amphibole geobarometer.The continuous breakdown of ilvaite with quartz to form ferro-actinolite and magnetite occur in the late retrograde stage(Stage II).The reactions occurred at 400440°C under moderate fO(ΔlgfO(HM):4 to 4.4).In Stage III,the breakdown of ilvaite to form calcite,pyrite 22 and ferroactinolite depends on XCO which can be estimated to be in a range of 0.005 to 0.05,and the reaction would 2 occur at higher temperatures with increasing XCO.Under these conditions,the breakdown occurs at 270350°C and 2 low fO(ΔlgfO(HM):up to 5.2).The thermodynamic model for continuous evolution from Stage I to Stage III 22 completely records the conditions of the retrograde alteration,which is inconsistent with the thermobarometry imprints of fluid inclusions.Therefore,the petrography and phase relations of ilvaite are useful indicators of reaction conditions in various skarn deposit types.
文摘Shangzhuang gold deposit located in the Wangershan fault zone of northwestern Jiaodong is of meso- hypogenic altered rock type. The ore bodies occur at the hanging wall and footwall of Wangershan fault in vein or irregular shapes with the NE strike, NW trend, 30° -60°~ in dip and the lateral trending of SW. The ores are composed of pyrite, quartz, sericite, bismuthinite, native gold, bismuth sulfosah minerals, chalcopyrite, etc. , shown as brecciated structure and vein structure with metasomatic dissolution textures. The wall rock altera- tion is mainly described as phyllic alteration and silicification. The mineralization of this deposit is controlled by structure and altered rocks. The ore-controlling fault structures of this deposit is Wangershan fault, of which the intersection of major fault and secondary fault is the main ore-bearing position of this gold deposit, and the lar- ger arc curved position is a favorable part for ore body occurrence. On the plane, the ore body is shown as equi- distant pinch-out reproduction.
