The Damoshan deposit is a small B-F-Sn Bi exoskarn deposit and contains a distinctive mineral assemblage comprising andradite,vesuvianite,calcite,diopside,magnetite,hematite,nordenskioldine,cassiterite,varlamoffite,sc...The Damoshan deposit is a small B-F-Sn Bi exoskarn deposit and contains a distinctive mineral assemblage comprising andradite,vesuvianite,calcite,diopside,magnetite,hematite,nordenskioldine,cassiterite,varlamoffite,schenfliesite,native bismuth,eulytite,bismite and bismuthite,in which the occurrence of eulytite is the first reported in China.Textures of the mineral paragenses show that andradite,vesuvianite and diopside were the earliest phases formed during metasomatism,i.e.,the skarn forming stage.Then nordenskioldine,magnetite and native bismuth,perhaps together with eulytite,were precipitated at the stage of retrograde alteration.The minerals varlamoffite,schoenfliesite,hematite ,bismite and bismuthite were probably the product of supergene alteration.The minerals were analyzed by means of electron microprobe.The data on the ,coexisting phases and their compositons show that during the metasomatism reduced F-and Sn-rich primary mineralizing solutions reacted with highly oxidized carbonated of the Gejie Formation,producing a high Fe^2+/Fe^3+ skarn(vesuvianite-fluorite skarn)near the contact of granite,and a low Fe^2+/Fe^3+ skarn(vesuvianite-fluorite skarn)near the contact of granite,and a low Fe^2+/Fe^3+ skarn(andradite skarn)in the outer zone of the skarn body in which andradite is extremely tin-bearing up to 5.14 wt% SnO2),In the retrograde alteration stage ,B-rich,but F-and Si-deficient mineralizing solutions replaced the tin-bearing andradite,forming an association of nordenskioldine and magnetite,No sulphides were deposited at this stage because of the oxidization ambient conditions in the andradite skarn.In the spergene oxidation zone,the nordenskioldine was dissolved into varlmoffite and calcite,the native bismuth was transformed into bismite or bismuthite ,and the magnetite was altered into hematite under the action of the CO2-rich supergene solutions.展开更多
Two principal hydrothermal events have been recognized ,which resulted in the tin-bearing skarns at Red-A-ven ,Northwest Dartmoor.Tin was enriched during both the early (occurring as tin-bearing andradite) and late hy...Two principal hydrothermal events have been recognized ,which resulted in the tin-bearing skarns at Red-A-ven ,Northwest Dartmoor.Tin was enriched during both the early (occurring as tin-bearing andradite) and late hydrothermal events (mainly as malayaite stannite and cassiterite,accompanied by boron silicates and minor tungsten).Thermometric measurements of fluid inclusions in diopside,garnet,malayaite,tourmaline-quartz and axinite were carried out,suggesting that the early skarns were formed at the temperature above 600℃and the salinities ranging from 10 to 20 wt.% NaCl eq.while the late skarns at the temperatures of 350-460℃ and the salinities ranging from 30 to 50wt.% NaCl eq.The estimated minimum depths are 2856m(850 bar) for the early event and 2526m(185 bar) for the late event.The birefringence of the andradite might be related with the superimposition of late hydrothermal fluids.展开更多
The Tongshan copper deposit at Guichi can be considered as a skarn-type copper deposit.Mul-ti-stage carbonatization was well developed in the skarn zone and copper-bearing orebodies,Mineralogy,mineral chemistry and st...The Tongshan copper deposit at Guichi can be considered as a skarn-type copper deposit.Mul-ti-stage carbonatization was well developed in the skarn zone and copper-bearing orebodies,Mineralogy,mineral chemistry and stable isotope data allow it to be divided into five stages:(1)carbonatization of single calcite crystals in the skarn stage;(2)calcite carbonatization in the oxide stage;(3)carbonatization in the early sulfide stage;(4)carbonatization in the late sulfide stage;and (5)carbonatization in the post-sulfide stage.Carbonatization in the early sulide stage is ,among other things,closely related to copper mineralization and is one of the alteration indicators of copper mineralization of this type.C.O,Rb and Sr isotopic studies indicate that the cakites of skarn and oxide stages were formed from hydrothermal solutions predominated by magmatic water,and those of sulfide stage were formed from hydrothermal solutions mainly involving heated meteoric warer.The former was formed in the environment where ?o2(?o2>10^-33and 10^-33>?o2>10^-36)(pH=7-8)is high as compared with the latter(10^-35>?o2>10^-38;pH=5.7).展开更多
文摘The Damoshan deposit is a small B-F-Sn Bi exoskarn deposit and contains a distinctive mineral assemblage comprising andradite,vesuvianite,calcite,diopside,magnetite,hematite,nordenskioldine,cassiterite,varlamoffite,schenfliesite,native bismuth,eulytite,bismite and bismuthite,in which the occurrence of eulytite is the first reported in China.Textures of the mineral paragenses show that andradite,vesuvianite and diopside were the earliest phases formed during metasomatism,i.e.,the skarn forming stage.Then nordenskioldine,magnetite and native bismuth,perhaps together with eulytite,were precipitated at the stage of retrograde alteration.The minerals varlamoffite,schoenfliesite,hematite ,bismite and bismuthite were probably the product of supergene alteration.The minerals were analyzed by means of electron microprobe.The data on the ,coexisting phases and their compositons show that during the metasomatism reduced F-and Sn-rich primary mineralizing solutions reacted with highly oxidized carbonated of the Gejie Formation,producing a high Fe^2+/Fe^3+ skarn(vesuvianite-fluorite skarn)near the contact of granite,and a low Fe^2+/Fe^3+ skarn(vesuvianite-fluorite skarn)near the contact of granite,and a low Fe^2+/Fe^3+ skarn(andradite skarn)in the outer zone of the skarn body in which andradite is extremely tin-bearing up to 5.14 wt% SnO2),In the retrograde alteration stage ,B-rich,but F-and Si-deficient mineralizing solutions replaced the tin-bearing andradite,forming an association of nordenskioldine and magnetite,No sulphides were deposited at this stage because of the oxidization ambient conditions in the andradite skarn.In the spergene oxidation zone,the nordenskioldine was dissolved into varlmoffite and calcite,the native bismuth was transformed into bismite or bismuthite ,and the magnetite was altered into hematite under the action of the CO2-rich supergene solutions.
文摘Two principal hydrothermal events have been recognized ,which resulted in the tin-bearing skarns at Red-A-ven ,Northwest Dartmoor.Tin was enriched during both the early (occurring as tin-bearing andradite) and late hydrothermal events (mainly as malayaite stannite and cassiterite,accompanied by boron silicates and minor tungsten).Thermometric measurements of fluid inclusions in diopside,garnet,malayaite,tourmaline-quartz and axinite were carried out,suggesting that the early skarns were formed at the temperature above 600℃and the salinities ranging from 10 to 20 wt.% NaCl eq.while the late skarns at the temperatures of 350-460℃ and the salinities ranging from 30 to 50wt.% NaCl eq.The estimated minimum depths are 2856m(850 bar) for the early event and 2526m(185 bar) for the late event.The birefringence of the andradite might be related with the superimposition of late hydrothermal fluids.
文摘The Tongshan copper deposit at Guichi can be considered as a skarn-type copper deposit.Mul-ti-stage carbonatization was well developed in the skarn zone and copper-bearing orebodies,Mineralogy,mineral chemistry and stable isotope data allow it to be divided into five stages:(1)carbonatization of single calcite crystals in the skarn stage;(2)calcite carbonatization in the oxide stage;(3)carbonatization in the early sulfide stage;(4)carbonatization in the late sulfide stage;and (5)carbonatization in the post-sulfide stage.Carbonatization in the early sulide stage is ,among other things,closely related to copper mineralization and is one of the alteration indicators of copper mineralization of this type.C.O,Rb and Sr isotopic studies indicate that the cakites of skarn and oxide stages were formed from hydrothermal solutions predominated by magmatic water,and those of sulfide stage were formed from hydrothermal solutions mainly involving heated meteoric warer.The former was formed in the environment where ?o2(?o2>10^-33and 10^-33>?o2>10^-36)(pH=7-8)is high as compared with the latter(10^-35>?o2>10^-38;pH=5.7).
