Environmental Geochemical Characteristics Of Hot Springs In The Tashkurgan Fault Zone In Xinjiang

The hydrogeochemical method is an effective tool to study the chemical characteristics and evaluation of the hot spring water.Due to the hostile geographical conditions that the average altitude of the Taxkorgan area is greater than 3.5 km,the development and utilization of the hot springs are poor,and the local residents directly use the hot springs as water for domestic and agricultural purposes.Therefore,we evaluated the hot springs in this area with national water quality standards.According to the results of water quality evaluation and the measurements of water chemistry,which includes the main elements,trace elements,?D and?¹⁸O and ⁸⁷Sr/⁸⁶Sr in the hot spring water samples collected in the Tashkorgan fault zone in Xinjiang in September 2018,chemical classification of the hot spring waters,the sources of ions and the water-rock interaction were hydrogeochemically discussed in order to provide a scientific basis for the rational using of local hot spring resources.The following remarks are concluded:(1)The evaluation results for major elements show that all hot spring waters are not suitable for direct drinking and agricultural water sources.The concentrations of trace elements were generally low,except for the potential health risks of B and As owing to the natural abnormally high values.The comprehensive water quality indexes of trace elements showed that the water quality grade is between Class I and Class II,and the water quality was relatively primitive.The concentrations of other toxic heavy elements such as Hg and Pb is very low,which were mainly derived from the surrounding rock of gneiss,alkaline syenite and granite.The elements of Li,B,and F in the hot springs are beneficial to the human body,which reach the medical hot spring standards in some hot springs.(2)The types of the hot spring water samples were HCO3-Ca,HCO3-Na,SO4-Na.The concentrations of Cl,Br and NO3 were lower,but the higher content of F in the all water samples.The concentration of Si O2 was relatively high,ranging from 20.0?53.1mg/L,and the isotopic ratios of strontium were in the range of 0.708779?0.717837,which indicated sources of the carbonate rock and the silico-aluminous rocks.(3)The characteristics of?D and?¹⁸O show that the waters were mainly derived from local atmospheric precipitation,and the replenishment elevation was estimated to be 4.3?4.8 km,indicating the evaporation characteristics of the plateau arid-semi-arid climate.The average circulation depth was estimated as 1.7km.The silicon-enthalpy model showed that the hot spring waters were mixed with the shallow cold water in varying degrees during upwards migration.