Hydrochemical Characteristics And Genesis Analyses Of The Hot Springs In The Batang Area Of Sichuan Province

The western area of Sichuan Province is located on the eastern margin of the geothermal zone of southern Tibet-western Sichuan-Western Yunnan.There are many hot springs,some of which are high-temperature hot springs.The Batang area,located in the westernmost part of Sichuan province,has strong tectonic movement,widespread granite and deep river valleys,which are conducive to the formation of hot spring.This article focuses on the Chaqingka hot spring,Chaluo hot spring and Duoge hot spring in the Batang county.Rare high-temperature geysers occur at Chaluo spring.The study of the hydrochemical characteristics and genesis of these hot springs can not only enrich the understanding of the geothermal resources of the thermal groundwater circulation and geysers in the western Sichuan region,but also provide a scientific basis for the development and utilization of local geothermal resources.The study area is mainly underlain by the Permian and Triassic strata.The formation of hot springs are controlled by the Chaluo-Songduo,Chalong-Ranbu and other faults.The temperature of hot springs in the study area ranges from 45 to 89?,the pH from 4.3to 8.1,and the TDS form 394 to 1296 mg/L.The dominant cation is Na⁺,while the anions are HCO₃^-.Most of hot water samples belong to HCO₃-Na type.Hot springs are rich in H₂SiO₃ and F^-.Bathing in the hot spring water has a good effect on skin diseases,but it is not potable.The F^-content has a positive correlation with pH and temperature.Among the trace elements in hot springs,Li,Rb and Cs are group IA elements,Sr and Ba are group IIA elements,so their content have similar distribution characteristics.Higher concentrations of Ca²⁺,HCO₃^-,CO₂ and P_CO2O2 values greatly promote the deposition of travertine in the Duoge hot spring.The?²H and?¹⁸O data show that the three hot springs are all meteoric in origin.The recharge area altitude is estimated as 4400-4800 m.The temperature is about-12--10?.The recharge area is the snow-capped mountains which exist near the hot springs,such as the Mountain Haizi and Mountain Harase.Using SiO₂ geothermometers,cation geothermometers and circulation formula,the temperature of the geothermal reservoirs of the Chaluo hot spring is estimated to be about 150-190?,the circulation depth range from 2537 to 3483 m,and the temperatures of geothermal reservoirs of the Duoge hot spring and Chaqingka hot spring is about 109-139?,the circulation depth is more than2000 m.According to the silicon germanium equation method,it is estimated that the mixture ratio of cold water of the Duoge hot spring and Chaqingka hot spring is ranges between 70 and 80%.The vents of the Chaluo hot spring in the northeast has a pebble layer with good permeability and mixed greater.As a result,the temperatures are lower;the vents in the southwest part emerge in granite,the cold water is mixed less,and the temperature of the vents are higher.The SC103-10 vent of the Chaluo hot spring is a high-temperature geyser which has a 1-minute eruption period and a 20-minute eruption interval.Due to the existence of thick limestone near the spring,groundwater dissolve the limestone to form cavities.The shallow cold water and the deep hot water are mixed in the caves to form a geyser.The causes of the three hot springs in the study area are similar.The thermal groundwater obtained infiltration from atmospheric precipitation and snow water in the mountain areas.After being heated by heat flow from below during the deep circulation process,the hot water emerges due to high temperature and high pressure along the fault zones in the river valleys.The hot springs in study area have great economic value.