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
Hydrogen isotope kinetic fractionation in the ilvaite and water system has been studied experimentally at 350-650℃. The result of study shows that the exchange mechanism of hydrogen isotope between ilvaite and water ...Hydrogen isotope kinetic fractionation in the ilvaite and water system has been studied experimentally at 350-650℃. The result of study shows that the exchange mechanism of hydrogen isotope between ilvaite and water is dominated by hydrogen diffusion.The activation energy for hydrogen diffusion in ilvaite is 118.4 kJ/mol for cylinder model and 115.5 kJ/mol for plate model, respectively.The activation energy for hydrogen isotope exchange in ilvaite is 122.6 kJ/mol.The closure temperature for the cessation of hydrogen isotope exchange between ilvaite and water is much lower than its formation temperature.So, after ilvaite crystallizes, the hydrogen isotope exchange between ilvaite and late hydrothermal solution will continue to take place.展开更多
A lot of experimental studies have been made on hydrogen isotope fractionation for hydrous minerals, such as mica, amphibole, epidote-group minerals, serpentine, aluminous-chlorite etc., since the 1970s. This plays an...A lot of experimental studies have been made on hydrogen isotope fractionation for hydrous minerals, such as mica, amphibole, epidote-group minerals, serpentine, aluminous-chlorite etc., since the 1970s. This plays an important role in the development of hydrogen isotope geochemistry. We have first made the experimental study on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.
基金Project supported by the National Natural Science Foundation of China.
文摘Hydrogen isotope kinetic fractionation in the ilvaite and water system has been studied experimentally at 350-650℃. The result of study shows that the exchange mechanism of hydrogen isotope between ilvaite and water is dominated by hydrogen diffusion.The activation energy for hydrogen diffusion in ilvaite is 118.4 kJ/mol for cylinder model and 115.5 kJ/mol for plate model, respectively.The activation energy for hydrogen isotope exchange in ilvaite is 122.6 kJ/mol.The closure temperature for the cessation of hydrogen isotope exchange between ilvaite and water is much lower than its formation temperature.So, after ilvaite crystallizes, the hydrogen isotope exchange between ilvaite and late hydrothermal solution will continue to take place.
基金Project supported by the National Natural Science Foundation of China.
文摘A lot of experimental studies have been made on hydrogen isotope fractionation for hydrous minerals, such as mica, amphibole, epidote-group minerals, serpentine, aluminous-chlorite etc., since the 1970s. This plays an important role in the development of hydrogen isotope geochemistry. We have first made the experimental study on
