Experimental Study On Formation Mechanisms Of Hydrochemical Components In Xifeng Hot Spring,guizhou Province By Water Rock Reaction

Hot springs are a clean and environmentally friendly renewable geothermal resource,often widely used in heating,refrigeration,healthcare,and various forms of industry and agriculture.They have high therapeutic value due to their rich special chemical components and trace elements that are beneficial to human health.Guizhou Xifeng Hot Spring is a famous mineral water resource for physical therapy both domestically and internationally.Due to its rich chemical components,it has significant therapeutic effects.As early as the 1950s,the Guizhou Provincial Federation of Trade Unions established a sanatorium here and has been in use ever since.It has also been awarded the title of"National Model Worker Sanatorium".During the 14th Five Year Plan period,Guizhou selected Xifeng Hot Spring as a pilot project for geothermal heating in Guizhou based on its resource endowment characteristics.Based on the above,Xifeng Hot Spring not only plays a significant role in healthcare and health tourism,but also plays an important role in the development and utilization of clean energy.Therefore,the scientific development and utilization of Xifeng Hot Spring is of great significance for promoting high-quality development of local economy and achieving the"dual carbon"goal.However,previous studies on Xifeng Hot Spring focused on the geological origin and hydrogeochemical characteristics of the formation of hot springs,and little was known about the migration and enrichment of elements during the evolution of hot springs.The research on the formation mechanism of hydrochemical components based on water rock reaction is weak,which is worthy of further study.In this paper,Xifeng Hot Spring is selected as the research object.By collecting hot spring water samples in the study area for hydrochemical analysis and collecting thermal reservoir and cap rock samples for petrogeochemical analysis,four different types of rocks,including algal debris dolomite in the bottom layer of the thermal reservoir,siliceous dolomite in the middle layer,dolomite at the top layer and black shale in the cap layer,are targeted at at different reaction times Exploring the formation mechanism of chemical components in Xifeng Hot Spring water through leaching experiments under different p H and CO₂ addition conditions.This study can provide scientific support for the development,utilization,planning,and management of Xifeng Hot Spring.The main research conclusions of this paper are as follows:（1）The water temperature of Xifeng Hot Spring is between 38～49℃,which belongs to low-temperature geothermal resources.The Si O₂ temperature scale is used to estimate the thermal storage temperature as 99℃.The p H is between 7.10～7.71,belonging to weakly alkaline water.The hydro-chemical type is Ca-Mg-HCO₃ type,with the main cations being Ca²⁺and Mg²⁺,and the main anions being HCO₃^-and SO₄^2-.Comparing the hydro-chemical composition data of Xifeng Hot Spring from 2011 to 2018,it is shown that the concentration values of various chemical components in Xifeng Hot Spring water have been stable over the years.（2）Under the conditions of thermal storage temperature,the water rock reaction experiments of the Xifeng Hot Spring thermal reservoir and cover rocks show that with the increase of p H,the leached calcium and magnesium ions gradually decrease,while the sodium ions gradually increase;The p H of the solution has negligible effect on the dissolution of K⁺.In addition,compared to the pure water experiment,the addition of CO₂ resulted in a higher leaching amount of potassium,sodium,calcium,and magnesium ions at different reaction times than the pure water experiment.When the water rock reaction time and temperature are the same,the acidic solution has the highest degree of dissolution on the original rock,followed by the solution with CO₂,and the pure water solution has the lowest degree of dissolution on the original rock.（3）According to the water rock reaction experiment,combined with the hydrochemical composition and rock geochemical composition in the area,the results show that the Ca²⁺,Mg²⁺,HCO₃^-ions in the hydrochemical composition of Xifeng Hot Spring mainly come from the dissolution reaction of carbon dioxide to the thermal storage dolomite;The K⁺ions mainly come from the dissolution of potassium salts in the cover layer;Na⁺ions mainly come from the exchange reaction between aluminosilicate and clay minerals like cations in thermal reservoir caprock;Sr²⁺and SO₄^2-ions mainly come from the dissolution of gypsum minerals and associated minerals such as celestite in the Loushanguan Formation of the Cambrian.（4）The geothermal wells and pipeline facilities of Xifeng Hot Springs may have celestite scaling.The high concentration of sulfate ions and trace components of"strontium"in the water of Xifeng Hot Springs may cause celestite precipitation during the development and utilization of hot springs.Therefore,it is necessary to pay attention to and strengthen monitoring to promote the sustainable and efficient use of hot spring water resources.