Chemical and isotopic data were measured for 51 leached brine springs in the Changdu-Lanping-Simao Basin(CD-LP-SM),China.The predominance of Cl and Na,saturation indices of carbonate minerals,and Na/Cl and Ca/SO4 rati...Chemical and isotopic data were measured for 51 leached brine springs in the Changdu-Lanping-Simao Basin(CD-LP-SM),China.The predominance of Cl and Na,saturation indices of carbonate minerals,and Na/Cl and Ca/SO4 ratios of^1 suggest that halite,sulphate,and carbonate are the solute sources.Integration of geochemical,δ18 O,andδD values suggests that springs are mainly derived from meteoric water,ice-snow melt,and water-rock interactions.B concentrations range from 0.18 to 11.9 mg/L,withδ11 B values of-4.37‰to+32.39‰,indicating a terrestrial source.Theδ11 B-B relationships suggest B sources of crustal origin(marine carbonates with minor crust-derived volcanics);we did not identify a marine or deep mantle origin.Theδ11 B values of saline springs(+4.61‰to+32.39‰)exceed those of hot(-4.37‰to+4.53‰)and cold(-3.47‰to+14.84‰)springs;this has contributed to strong water-rock interactions and strong saturation of dissolved carbonates.Conversely,the global geothermalδ11 B-Cl/B relationship suggests mixing of marine and non-marine sources.Theδ11 B-Cl/B relationships of the CD-LP-SM are similar to those of the Tibet geothermal belt and the Nangqen Basin,indicating the same B origin.These differ from thermal waters controlled by magmatic fluids and seawater,suggesting that B in CD-LP-SM springs has a crustal origin.展开更多
The northern Tibet plateau is the core of generalized Qinghai—Tibet plateau. The main part of Qiangtang—Changdu massif, which is 45×10 4km 2 and more than 5000m in altitude, conforms to the northern Tibet plate...The northern Tibet plateau is the core of generalized Qinghai—Tibet plateau. The main part of Qiangtang—Changdu massif, which is 45×10 4km 2 and more than 5000m in altitude, conforms to the northern Tibet plateau in area.1 The shape features and boundary conditions of Qiangtang—Changdu massif\;(1) Qiangtang—Changdu massif shows huge flat\|lying “S” area In MSS7 mosaic image, Qiangtang—Changdu massif extends in west and east, and appears a long\|elliptic huge block composed of feathered and dendritic textures.. Noticeably, there are two similar texture “tails" in the west and east ends of the massif. The western tail turns and constringes to the north, and eastern tail to the south. Thereby, the massif shows huge “S" area. According to the regional analysis, the eastern tail locates between Shaluli Mt.\|Taniantaweng Mt. and Mujiang River, and western part through Bangong\|Co connects with Pamirs along Karakoram Mt. In regional tectonics, the massif locates between Lazhulong\|Xijinwulan\|Co\|Jinshajiang River and Bangong\|Co\|Dongqiao\|Nujiang River fault belts.展开更多
Research on the origin of carbonates in Changdu Basin holds significant importance for understanding the regional potash formation model.Based on a comprehensive review of previous studies,field geological surveys,and...Research on the origin of carbonates in Changdu Basin holds significant importance for understanding the regional potash formation model.Based on a comprehensive review of previous studies,field geological surveys,and laboratory investigations,this study analyzes the origin and properties of carbonates within the context of regional potash formation.Petrographic studies show that magnesite deposits,with the characteristics of sedimentary origin.The results of elemental geochemical analysis show that the carbonates in this area were formed in the sedimentary environment via evaporation followed by concentration,and the formation of magnesite was possibly caused by the substitution of calcium in the dolomite with magnesium-rich brine.Theδ^(13)C values of carbonats in the study area are between5.9‰and 9.1‰.Theδ^(18)O values of magnesite samples range from-7.3‰to-1.3‰,and theδ^(18)O values of dolomites range from-10.3‰to-8.4‰.All the calculated Z values of oxygen isotopes of carbonates greater than 120.A comprehensive analysis of carbon and oxygen isotopes indicates that the magnesite was formed in a highly concentrated Marine sedimentary environment and does not show any relation with the metasomatism of hydrothermal fluids.The results on the correlation of magnesite with seawater and its sedimentary origin provide key information for explaining the migration direction of brine between the Changdu and Lanping-Simao Basins.The residual metamorphic seawater in the Changdu Basin migrated to the Lanping-Simao Basin,where potash underwent deposition.Whereas,magnesite and dolomite in the early stage of potash formation were left in the Changdu Basin.展开更多
基金funded by the National Key Basic Research Project of China(973 program,No.2011CB403004)
文摘Chemical and isotopic data were measured for 51 leached brine springs in the Changdu-Lanping-Simao Basin(CD-LP-SM),China.The predominance of Cl and Na,saturation indices of carbonate minerals,and Na/Cl and Ca/SO4 ratios of^1 suggest that halite,sulphate,and carbonate are the solute sources.Integration of geochemical,δ18 O,andδD values suggests that springs are mainly derived from meteoric water,ice-snow melt,and water-rock interactions.B concentrations range from 0.18 to 11.9 mg/L,withδ11 B values of-4.37‰to+32.39‰,indicating a terrestrial source.Theδ11 B-B relationships suggest B sources of crustal origin(marine carbonates with minor crust-derived volcanics);we did not identify a marine or deep mantle origin.Theδ11 B values of saline springs(+4.61‰to+32.39‰)exceed those of hot(-4.37‰to+4.53‰)and cold(-3.47‰to+14.84‰)springs;this has contributed to strong water-rock interactions and strong saturation of dissolved carbonates.Conversely,the global geothermalδ11 B-Cl/B relationship suggests mixing of marine and non-marine sources.Theδ11 B-Cl/B relationships of the CD-LP-SM are similar to those of the Tibet geothermal belt and the Nangqen Basin,indicating the same B origin.These differ from thermal waters controlled by magmatic fluids and seawater,suggesting that B in CD-LP-SM springs has a crustal origin.
文摘The northern Tibet plateau is the core of generalized Qinghai—Tibet plateau. The main part of Qiangtang—Changdu massif, which is 45×10 4km 2 and more than 5000m in altitude, conforms to the northern Tibet plateau in area.1 The shape features and boundary conditions of Qiangtang—Changdu massif\;(1) Qiangtang—Changdu massif shows huge flat\|lying “S” area In MSS7 mosaic image, Qiangtang—Changdu massif extends in west and east, and appears a long\|elliptic huge block composed of feathered and dendritic textures.. Noticeably, there are two similar texture “tails" in the west and east ends of the massif. The western tail turns and constringes to the north, and eastern tail to the south. Thereby, the massif shows huge “S" area. According to the regional analysis, the eastern tail locates between Shaluli Mt.\|Taniantaweng Mt. and Mujiang River, and western part through Bangong\|Co connects with Pamirs along Karakoram Mt. In regional tectonics, the massif locates between Lazhulong\|Xijinwulan\|Co\|Jinshajiang River and Bangong\|Co\|Dongqiao\|Nujiang River fault belts.
基金the financial support from the Second Tibetan Plateau Scientific Expedition and Research(Grant No.2019QZKK0805)the postdoctoral project of Qinghai Institute of Salt Lakes(Grant No.E260DZ0401)+1 种基金the Kunlun Talent Project in Qinghai Province(Grant No.E340DZ0801)the Qinghai Provincial Department of Science and Technology Project(Grant No.2024-ZJ-722)。
文摘Research on the origin of carbonates in Changdu Basin holds significant importance for understanding the regional potash formation model.Based on a comprehensive review of previous studies,field geological surveys,and laboratory investigations,this study analyzes the origin and properties of carbonates within the context of regional potash formation.Petrographic studies show that magnesite deposits,with the characteristics of sedimentary origin.The results of elemental geochemical analysis show that the carbonates in this area were formed in the sedimentary environment via evaporation followed by concentration,and the formation of magnesite was possibly caused by the substitution of calcium in the dolomite with magnesium-rich brine.Theδ^(13)C values of carbonats in the study area are between5.9‰and 9.1‰.Theδ^(18)O values of magnesite samples range from-7.3‰to-1.3‰,and theδ^(18)O values of dolomites range from-10.3‰to-8.4‰.All the calculated Z values of oxygen isotopes of carbonates greater than 120.A comprehensive analysis of carbon and oxygen isotopes indicates that the magnesite was formed in a highly concentrated Marine sedimentary environment and does not show any relation with the metasomatism of hydrothermal fluids.The results on the correlation of magnesite with seawater and its sedimentary origin provide key information for explaining the migration direction of brine between the Changdu and Lanping-Simao Basins.The residual metamorphic seawater in the Changdu Basin migrated to the Lanping-Simao Basin,where potash underwent deposition.Whereas,magnesite and dolomite in the early stage of potash formation were left in the Changdu Basin.
基金supported by the China Geological Survey Project "An Integrated Study on Precambrian Geology and Paleo-zoic Tectono-Palaeogeography in Tibetan Plateau" (1212010610102)
