Geochemical Characteristics And Genesis Of Brine From Hadahexiu Salt Lake,Inner Mongolia

Inner Mongolia is one of the four major salt lakes distribution area in China.Hada Hexiu is a modern dry salt lake,which located in the Ejina Basin in the Alxa Plateau in western Inner Mongolia.Through geological exploration,it is found that there are pore brines of the Pleistocene of the Pleistocene in the underground.At present,there is insufficient research on the geochemical characteristics of the brines.The author collected samples from underground brine,Heihe River,lake water and rainwater in the study area,and analyzed the constant and trace ion content,total dissolved solids?TDS?,and hydrogen and oxygen isotopic compositions of the samples.Compared with previous research results,the geochemical characteristics of brine are analyzed,and the origin and evolution of brine are discussed.It provides basic information for the subsequent resource exploration,development and utilization,and environmental protection in the study area.The salt lake brine is weakly alkaline,the degree of mineralization is medium-low,and the water chemical type is sodium sulfate subtype.The major ions in the brine are mainly Na⁺,Mg²⁺,SO₄^2-,and Cl^-.The content of B³⁺in the trace ions is the highest,and the ion concentration distribution is uneven.High values of constant and trace ions in the brine appear in the center of the lake basin,while the contents of ions in the edge of the lake basin are low.The average K⁺content in the brine is 1.60 g/L,which meets the standard for comprehensive utilization.The K⁺/TDS ratio shows that the brine has the characteristics of high potassium content and low mineralization.The author also analyzed the sodium chloride coefficient?0.79?6.15?and bromine chloride coefficient?0.11?1.81?of the ions in the brine,and revealed that the origin of the brine is mainly the leaching of evaporite.The content of K⁺,B³⁺,and Li⁺in the residual brine after evaporation of brine in the study area exceeded its industrial mining index,and Br-has reached the comprehensive utilization standard,which has the significance of resource development.Based on the distribution of the hydrogen and oxygen isotopes in the underground brine and lake water,both of which are positive,the authors conclude that they accept the supply of Heihe River.The deuterium surplus of brine and lake water has a negative correlation with the TDS,indicating that the underground brine of Hadahexiu Salt Lake has been evaporated,and the deuterium surplus of the brine is smaller than that of the lake water,revealing that the brine has been subjected to evaporation and evaporite leaching.Together,the hydrogen and oxygen isotope fractionation occurred.Based on the hydrochemical characteristic coefficient and the hydrogen and oxygen isotope composition of the brine,the author preliminary discussed the origin and source of underground brine in the study area,and believed that the replenishment of the brine was mainly from the Heihe River.The river water was evaporated during the process of replenishing the brine,and the evaporite in the strata were leached.Finally,combining the three factors of structure,material source,and climate,the author comprehensively analyzed the possible genesis model of brine in Hadahexiu Salt Lake.