Genesis and geological significance of carbonate in Changdu Basin,Xizang,China:Constraints from geochemistry and C-O isotopes  

作　　者：Wenhua Han Yongshou Li Haizhou Ma Huaide Cheng Binkai Li Qinyu Hai Xuahai Ma 

机构地区：[1]Key Laboratory of Comprehensive and Highly Effi cient Utilization of Salt Lake Resources,Qinghai Institute of Salt Lakes,Chinese Academy of Sciences,Xining 810008,China [2]Qinghai Provincial Key Laboratory of Geology and Environment of Salt Lakes,Xining 810008,China

出　　处：《Acta Geochimica》2024年第6期1192-1204,共13页地球化学学报（英文）

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);the Kunlun Talent Project in Qinghai Province(Grant No.E340DZ0801);the Qinghai Provincial Department of Science and Technology Project(Grant No.2024-ZJ-722)。

摘　　要：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.

关 键 词：Changdu basin CARBONATITE GEOCHEMISTRY Mineral deposit genesis Significance of potash formation 

分 类 号：P59[天文地球—地球化学] P588.245[天文地球—地质学]