A Study Of Hydrochemcial And Isotopic Characteristics And Formation Of Some Of The Hot Springs In The Lincang Area Of Yunnan

The Lincang area is located in the southwestern part of Yunnan Province and lies in the Yunnan-Tibet geothermal belt.A lot of hot springs occur in the area where geothermal resources are abundant.The structural deformation is complex in the area.It basically shows the complex anticline structure.The fold axis in the is north-south direction and the geothermal reservoir is composed of the Lincang Granite.Some hot springs in Lincang area and investigated,including the Lincang hot spring,the Zhafanghe hot spring,the Malutianba hot spring,the Dengjiazhuang hot spring,the Reshuitang hot spring,the Dakongbang hot spring,the Daxing hot spring and the Xiqian hot spring.The hot springs in the study area include both high-temperature hot springs and medium-low temperature hot springs,among which the high-temperature hot springs emerge in the form of spouting springs.Through studies of the characteristics of the hydrochemistry and isotopes and genetic analysis of the hot springs in the study area,it is of great significance for promating the development and utilization of the local geothermal resources.Water temperature of the eight hot springs ranges from 50.2 to 96?.The hydrochemical characteristics of the hot spring water are as follows:TDS=0.625-0.702 g/L,pH=6.7-9,Eh=-327--34 mV.The main cations in the hot water are K⁺,Na⁺,Ca²⁺and Mg²⁺,and the main anions are Cl^-,SO₄^2-and HCO₃^-.Li and Sr are relatively abundant and good for health.By using the software of AquaChem,the hydrochemical types are mainly of HCO₃·SO₄-Na and HCO₃-Na type.The contents of H₂SiO₃ and F^-in the hot spring water are relatively high,and the content of H₂SiO₃ranges from 80.08 mg/L to 211.6 mg/L,meeting the standard concentration of mineral water in the physiotherapy,and the hot water can be named as silicic acid water.Except the F^-of YLC17 of 0.614 mg/L,the contents F^-of the other hot spring water samples exceeds 2 mg/L,as fluorine water and cannot be directly consumed.In the study area,the?²H and?¹⁸O contents of the hot water samples indicate that they are of meteoric origin.The elevations of the recharge are are estimated as 1600-2100m and the temperature of recharge are arecalculated as about 2.4-5.8?.By using ²²⁶Ra-²²²Rn method,the ages of underground hot water are estimated as about 47-470 a.The geothermal reservoir temperatures are arecalculated as116-177?.The circulation depths of the thermal groundwater are approximately2100-3500 m.The formation of the hot spring can be summarized as that after receiving recharge from precipitation in the surrounding mountain areas,the groundwater under goes deep circulation and is heated by heat flow,the geothermal water rises along the fracture zone,then mixes with the shallow groundwater,finally occurs in the form of hot springs.Among them,the high temperature hot springs are exposed to the surface as boiling springs of high temperature,the heat is indirectly come from the deep magma.