Field observations demonstrate that calc-sinters occurred in the lakes of Badain Jaran Desert. 87Sr/86Sr ratios,14C,δ 13C and mineral com-positions of calc-sinters,and 3He/4He,4He/20Ne,δ 18O,δ D,pH and TDS of water...Field observations demonstrate that calc-sinters occurred in the lakes of Badain Jaran Desert. 87Sr/86Sr ratios,14C,δ 13C and mineral com-positions of calc-sinters,and 3He/4He,4He/20Ne,δ 18O,δ D,pH and TDS of water from springs and lakes are analyzed in detail. The results indicate that the lake water is supplied through deep fault zone. The “ker-nel” of stabilized dunes in the Badain Jaran Desert perhaps consists of calc-sinters and calcareous ce-mentation layers. Deep-seated groundwater effuses from this “kernel” and recharges to lakes in desert. Precipitation and snowmelt water from the Qing-hai-Tibet Plateau is fed into the Badain Jaran Desert,Gurinai,Wentougaole and Ejinqi areas through the Xigaze-Langshan Fault zone. The isotopic composi-tions of groundwater in the Alax Plateau are abnor-mal due to the strong evaporation of the Gyaring and Ngoring lake water in the headstream of the Yellow River. Groundwater dissolves dissoluble fractions of rocks during its transportation through the fault zone and flows out of the mouth of spring in the Badan Jaran Desert. The dissoluble fractions are finally de-veloped into calc-sinters and calcareous cementation layers around the spring. Calci-sinters are gradually largened and eventually emerge on the surface of lake water. Eolian sands accumulate on the surfaces of calc-sinters and calcareous cementation layers,and eventually develop into dunes. Invasion of magma causes an increase in the temperature of groundwater within the faults. Groundwater evapora-tion provides water vapor for the formation of humid stabilized dunes during its upwelling. Rhizoconcre-tions found in Yihejigede indicate that the dune was formed and remained immovable 4700 years ago. The height of the megadunes is proportional to thermal quantity carried by the groundwater.展开更多
The Yangla copper deposit, located in western Yunnan Province, China, is a typical giant, newly started mining copper deposit with an estimated Cu reserves of about 1,200,000 tons. The deposit is spatially and tempora...The Yangla copper deposit, located in western Yunnan Province, China, is a typical giant, newly started mining copper deposit with an estimated Cu reserves of about 1,200,000 tons. The deposit is spatially and temporally associated with the Linong granodiorite, which is rich in SiO2 （SIO2=58.25 wt%-69.84 wt%） and alkalis （Na20＋K20=5.98 wt%-8.34 wt%）, indicating an association with shoshonitic series to high-K calc-alkaline series granites, and shows low contents of TiO2 （0.35 wt%- 0.48 wt%）, MgO （1.51 wt%-1.72 wt%）, and A1203 （13.38 wt%-19.75 wt%）. The 34S values of sulfides of the main ore stage from copper ores vary range from -4.2%o to -0.9%o, indicating a much greater contribution from the mantle to the ore-forming fluids. The 34S values of the late ore stage is -9.8%0, indicating enrichment of biogenic sulfur which may derive from the crustal hydrothermal fluid. The 208pb/204pb, 207pb/204pb and 206pb/204pb of sulfides of the main ore stage from copper ores range within 38.66-38.73, 15.71-15.74 and 18.35-19.04, respectively, implying that the Pb was derived from the mantle, with the crustal component, probably representing mixtures of mantle lead and crustal lead. Sulfide of the late ore stage in their Pb isotopic composition, 208pb/204pb= 38.69, 207pb/204pb=15.70, 206Pb/204pb=18.35, implying that the Pb was derived from the crust. The Linong granodiorite is syn- collisional, produced by partial melting of thickened lower crust, which was triggered by the westward subduction of the Jinshajiang Oceanic plate. During a transition in geodynamic setting from collision- related compression to extension, gently dipping ductile shear zones （related to subduction） were transformed to brittle shear zones, consisting of a series of thrust faults in the Jinshajiang tectonic belt. The tensional thrust faults would have been a favorable environment for ore-forming fluids. The ascending magma provided a channel for the ore-forming fluid from the mantle wedge. After the magma arrived at the base of展开更多
Calc-sintersdistributed in the middle of lakes and rhizoconcretions scattered at the slopes of sand dunes were observed during three explorations to the Badain Jaran Desert in the past two years. Wet sands were also f...Calc-sintersdistributed in the middle of lakes and rhizoconcretions scattered at the slopes of sand dunes were observed during three explorations to the Badain Jaran Desert in the past two years. Wet sands were also found underneath the dry surface sand layers of about 20-50 cm in thickness. The geochemical parameters were measured on minerals and water samples collected from the Badain Jaran Desert and neighboring areas. The results show that the water system in the desert may be recharged from the groundwater originating from the precipitation of the Qilian Mountains and/or the Tibetan Plateau rather than the local rainfalls.展开更多
The barium deposits in Ankang and Xunyang counties,Shaanxi Province,China,occur in the northernmost part of the world-class barium metallogenic belt in south Qinling.The deposits are hosted by the Lower Silurian carbo...The barium deposits in Ankang and Xunyang counties,Shaanxi Province,China,occur in the northernmost part of the world-class barium metallogenic belt in south Qinling.The deposits are hosted by the Lower Silurian carbonaceous siliceous rocks,with a unique combination of barite and witherite.The homogenization temperatures of fluid inclusions in the barite are mainly concentrated between 135 and 155 ℃,whereas those from the witherite have two peaks of 165-175 ℃,and 215-225℃,respectively.Laser Raman analysis of fluid inclusions indicates that the vapor phase of fluid inclusions in barite is dominated by H_2O,although some contains N_2,H_2S,and CH_4.The compositions of the vapor and liquid phases of fluid inclusions in witherite can be divided into two end-members,one dominated by H_2O without other volatiles,and the other containing CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6 in addition to H_2O.CO_2,H_2S,and some CH_4 are interpreted as products of chemical reactions during mineralization.Organic gases（CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6） in the fluids were critical in the formation of barium sulfate versus carbonate.The δ^（34）S values of barite range from 38.26‰ to54.23‰（CDT）,the δ^（34）S values of sulfides coexisting with barium minerals vary from 22.44‰ to25.11‰（CDT）,and those in the wall rock from 11.60‰ to 19.06‰（CDT）.We propose that the SO_4^（2-）generally experienced bacterial sulfate reduction in seawater before mineralization,and some SO_4^（2-）also experienced thermochemical sulfate reduction in hydrothermal system during mineralization.The δ^（13）C values of witherite range from-27.30‰ to-11.80‰（PDB）,suggesting that carbon was sourced from organic substances（like CH_4,C_2H_4,and C_2H_6）.The formation of witherite was possibly associated with thermochemical sulfate reduction,which caused the consumption of the organic gases and SO_4^（2-） in the hydrothermal solutions,consequently inhibiting barite formation.The important conditions for forming展开更多
基金Acknowledgements This work was jointly supported by the Technical Cooperation Programme of International Atomic Energy Agency （Grant No. CPR/8/15）, the National Natural Science Foundation of China （Grant No. 50579017）, Advanced Research Programme of the National Natural Science Foundation of China （Grant No. 40442001） and Jiangsu Foundation for ＂Talents of Six Industries＂.
文摘Field observations demonstrate that calc-sinters occurred in the lakes of Badain Jaran Desert. 87Sr/86Sr ratios,14C,δ 13C and mineral com-positions of calc-sinters,and 3He/4He,4He/20Ne,δ 18O,δ D,pH and TDS of water from springs and lakes are analyzed in detail. The results indicate that the lake water is supplied through deep fault zone. The “ker-nel” of stabilized dunes in the Badain Jaran Desert perhaps consists of calc-sinters and calcareous ce-mentation layers. Deep-seated groundwater effuses from this “kernel” and recharges to lakes in desert. Precipitation and snowmelt water from the Qing-hai-Tibet Plateau is fed into the Badain Jaran Desert,Gurinai,Wentougaole and Ejinqi areas through the Xigaze-Langshan Fault zone. The isotopic composi-tions of groundwater in the Alax Plateau are abnor-mal due to the strong evaporation of the Gyaring and Ngoring lake water in the headstream of the Yellow River. Groundwater dissolves dissoluble fractions of rocks during its transportation through the fault zone and flows out of the mouth of spring in the Badan Jaran Desert. The dissoluble fractions are finally de-veloped into calc-sinters and calcareous cementation layers around the spring. Calci-sinters are gradually largened and eventually emerge on the surface of lake water. Eolian sands accumulate on the surfaces of calc-sinters and calcareous cementation layers,and eventually develop into dunes. Invasion of magma causes an increase in the temperature of groundwater within the faults. Groundwater evapora-tion provides water vapor for the formation of humid stabilized dunes during its upwelling. Rhizoconcre-tions found in Yihejigede indicate that the dune was formed and remained immovable 4700 years ago. The height of the megadunes is proportional to thermal quantity carried by the groundwater.
基金supported by the National Basic Research Program of China (2009CB421003,2009CB421005)by the 111 Project (Grant No. B07011)
文摘The Yangla copper deposit, located in western Yunnan Province, China, is a typical giant, newly started mining copper deposit with an estimated Cu reserves of about 1,200,000 tons. The deposit is spatially and temporally associated with the Linong granodiorite, which is rich in SiO2 （SIO2=58.25 wt%-69.84 wt%） and alkalis （Na20＋K20=5.98 wt%-8.34 wt%）, indicating an association with shoshonitic series to high-K calc-alkaline series granites, and shows low contents of TiO2 （0.35 wt%- 0.48 wt%）, MgO （1.51 wt%-1.72 wt%）, and A1203 （13.38 wt%-19.75 wt%）. The 34S values of sulfides of the main ore stage from copper ores vary range from -4.2%o to -0.9%o, indicating a much greater contribution from the mantle to the ore-forming fluids. The 34S values of the late ore stage is -9.8%0, indicating enrichment of biogenic sulfur which may derive from the crustal hydrothermal fluid. The 208pb/204pb, 207pb/204pb and 206pb/204pb of sulfides of the main ore stage from copper ores range within 38.66-38.73, 15.71-15.74 and 18.35-19.04, respectively, implying that the Pb was derived from the mantle, with the crustal component, probably representing mixtures of mantle lead and crustal lead. Sulfide of the late ore stage in their Pb isotopic composition, 208pb/204pb= 38.69, 207pb/204pb=15.70, 206Pb/204pb=18.35, implying that the Pb was derived from the crust. The Linong granodiorite is syn- collisional, produced by partial melting of thickened lower crust, which was triggered by the westward subduction of the Jinshajiang Oceanic plate. During a transition in geodynamic setting from collision- related compression to extension, gently dipping ductile shear zones （related to subduction） were transformed to brittle shear zones, consisting of a series of thrust faults in the Jinshajiang tectonic belt. The tensional thrust faults would have been a favorable environment for ore-forming fluids. The ascending magma provided a channel for the ore-forming fluid from the mantle wedge. After the magma arrived at the base of
基金This work is jointly supported by the TC item of LAEA(CPR/8/015)Academician Foundation of Hohai University(2002/05)as.well as the National Natural Science Foundation of China(40442001).
文摘Calc-sintersdistributed in the middle of lakes and rhizoconcretions scattered at the slopes of sand dunes were observed during three explorations to the Badain Jaran Desert in the past two years. Wet sands were also found underneath the dry surface sand layers of about 20-50 cm in thickness. The geochemical parameters were measured on minerals and water samples collected from the Badain Jaran Desert and neighboring areas. The results show that the water system in the desert may be recharged from the groundwater originating from the precipitation of the Qilian Mountains and/or the Tibetan Plateau rather than the local rainfalls.
基金funded by the National Natural Science Foundation of China(No.40730844)the National Basic Research Program of China(No.2009CB219500 and No.2009BC219508)
基金jointly supported by the National Natural Science Foundation of China(grant nos. 41173062 and 40573032)the 111 project under the Ministry of Education and the State Administration of Foreign Experts Affairs,China(grant no.B07011)
文摘The barium deposits in Ankang and Xunyang counties,Shaanxi Province,China,occur in the northernmost part of the world-class barium metallogenic belt in south Qinling.The deposits are hosted by the Lower Silurian carbonaceous siliceous rocks,with a unique combination of barite and witherite.The homogenization temperatures of fluid inclusions in the barite are mainly concentrated between 135 and 155 ℃,whereas those from the witherite have two peaks of 165-175 ℃,and 215-225℃,respectively.Laser Raman analysis of fluid inclusions indicates that the vapor phase of fluid inclusions in barite is dominated by H_2O,although some contains N_2,H_2S,and CH_4.The compositions of the vapor and liquid phases of fluid inclusions in witherite can be divided into two end-members,one dominated by H_2O without other volatiles,and the other containing CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6 in addition to H_2O.CO_2,H_2S,and some CH_4 are interpreted as products of chemical reactions during mineralization.Organic gases（CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6） in the fluids were critical in the formation of barium sulfate versus carbonate.The δ^（34）S values of barite range from 38.26‰ to54.23‰（CDT）,the δ^（34）S values of sulfides coexisting with barium minerals vary from 22.44‰ to25.11‰（CDT）,and those in the wall rock from 11.60‰ to 19.06‰（CDT）.We propose that the SO_4^（2-）generally experienced bacterial sulfate reduction in seawater before mineralization,and some SO_4^（2-）also experienced thermochemical sulfate reduction in hydrothermal system during mineralization.The δ^（13）C values of witherite range from-27.30‰ to-11.80‰（PDB）,suggesting that carbon was sourced from organic substances（like CH_4,C_2H_4,and C_2H_6）.The formation of witherite was possibly associated with thermochemical sulfate reduction,which caused the consumption of the organic gases and SO_4^（2-） in the hydrothermal solutions,consequently inhibiting barite formation.The important conditions for forming
