Chemical Characteristics And Provenance Analysis Of Geothermal Water In A Typical Geothermal Display Area In Angren County,Tibet

Angren County is located in the southwestern part of the Qinghai-Tibet Plateau,the eastern part of the Alps-Himalayan giant tectonic belt,across the tropical areas of Dangyayongcuo-Nyalam and Tagejia-Dagacuo.The geothermal resources are abundant,and the degree of theoretical research on the geothermal system is relatively low.Therefore,the research on the geochemistry and material sources of the underground hot water in the area is particularly important.On the one hand,the research results can clarify the distribution of resources in the area and improve the development and utilization of geothermal resources.To a certain extent,it can improve the current situation of resource scarcity and low urbanization;on the other hand,it can enrich the understanding of the formation mechanism of the geothermal system in the region,and provide theoretical basis for the subsequent possible drilling and investigation work and heat damage prevention work in railway construction.This paper selects 14 hot springs in the area with good exposure as the research object,collects and arranges the data of underground hot water and surface water;uses hydrochemical methods to analyze the chemical characteristics,evolution and the source of each component of the underground hot water;The isotope method was used to identify the hot water supply source,the range of the supply area,and the heat source;the geochemical thermometer and the silicon enthalpy model were used to explore the mixing of hot and cold water and the heat storage temperature;finally,the above analysis results were combined from the heat source and channel The formation mechanism of underground hot water in the study area is summarized in four aspects:water source and heat storage.Analysis of hydrochemical characteristics shows that the main hydrochemical type of underground hot water in the Angren geothermal display area is HCO₃-Na type,and the minor components Li,As,F,HBO₂,Si O₂and Cl are generally positively correlated,indicating the geothermal water in the study area There is mixing of water from deep magma,and the ion ratio coefficient and Gibbs diagram show that the underground hot water and the surrounding rock have had a strong leaching effect.Most of the Na,K,Ca,and Mg in the underground hot water come from the components filtered out from the surrounding rock during the previous atmospheric precipitation and the water seepage of snowmelt during the upwelling process of the hot water;HCO₃mainly comes from the geothermal water and Dissolution of carbonate wall rocks;SO₄mainly comes from underground hot water dissolving sulfate wall rocks;Cl mostly comes from deep magma.Using a geochemical thermometer,the temperature range of the thermal storage in the study area is 69.93?223.73?,and the temperature range of the deep thermal storage in the region is estimated to be 104?241?by using the silicon enthalpy mixing model.The mixing ratio of cold water in the underground hot water is:52%?85%.The analysis of isotope characteristics shows that atmospheric precipitation infiltration is the main source of replenishment of underground hot water in the study area,and there is an obvious D enrichment phenomenon in the Tagejia hot spring.The elevation effect indicates that the elevation range of the recharge area is 4557.5?4794 meters.Finally,comprehensive regional geological background,geophysical prospecting data and geochemical analysis results of underground hot water,taking Chazi Hot Spring as an example,propose a conceptual model map of the origin of hot springs.