Characteristics And Formation Of Some Of The Hot Springs In Tengchong County Of Yunnan

A kind of new clean energy, geothermal energy, is an enormous and important heat resource. The Tengchong County of Yunnan Province is one of several famous geot-hermal regions in China. Studies of the characteristics and formation of hot spings in Tengchong are of very important significance for enrichment of geothermal science and hydrogeology and for promoting the exploitation and utilization of geothermal resources.The Tengchong County is located in the east edge of the Burma arc tectonic belt and is in the south part of Qinghai-Tibet Plateau tectonic belt to the west side of Hengduan Mountains. In the study area, there is a variety of fractures and pyromagma in deep underground. These are advantages of forming hot springs of moderate to high temperature. This article mainly involves in four hot springs. Frog Mouth, Sisters Spring and Large Roll Pan vents are all located in the Rehai Scenic Area, and the hot water temperature is between 94.1℃ and 95℃. The Stone Wall hot springs are situated in the Stone Wall hot spring resort in Zaotang village of Jietou town; the hot water temperature is between 64.5℃ and 64.8℃. The Black Mud springs are situated in the southwest Heinitang in Guyong town; the hot water temperature is between 54.9℃ and 64℃. The Stone Flower Cave hot springs are located at 1.2 km of Eastern Shihuadong village of Guyong, and the hot water temperature is between 64.7℃ and 68.3℃. The discharge of the hot springs in the study area ranges from 0.2 to 10 L/s. The major ions in the hot water are sodium, potassium, calcium, bicarbonate, chloride and sulfate. The main hydrochemical types are of HCO3.Cl-Na type and HCO3-Na type; The TDS of the hot water ranges from 380 to 2998 mg/L; p H value is between 6.8 and 9.07; the content of H2 Si O3 is between 52.4 and 204 mg/L; the content of H2 Si O3, Li and Si in most hot springs are higher than that of the standard of mineral water. The F, HAs O3 and HBO2 indexes of part spring vents exceed the drinking standard, and the water is poisonous and undrinkable. Analyses of stable isotopes characteristics show that the geothermal water are of meteoric origin. The recharge elevation of the hot water is 1682 to 2911 m and the temperature in the recharge areas is 1.8℃ to 16.3℃, which are estimated by applying elevation effect and temperature effect of isotope; the calculated radium-radon age of the geothermal water is 13 to 32 a.The results of mineral saturation index show that quartz thermometric scale is more suitable for calculating the reservoir temperatures than chalcedony thermometric scale. The cold water mixing rations in the hot water are computed with the silicon-enthalpy formula method and the silicon-enthalpy graphic method; and the computation of these two methods is similar, which is 0.56 to 0.85. Using the Si O2 scale calculated the reservoir temperatures of this area is 137℃ to 253℃; the circulation depth of the hot water is 852 to 1748 m. The natural heat discharge of the hot springs is 9.21×1012 to 5.21×1013 J/a, which can be transferred into standard coal of 385.4 to 2179.9 t/a. Those three springs in Rehai Area are hot springs of high temperature which obtain heat through deep circulation of groundwater in granite, what is more, there is a magma pocket at depth; the Stone Wall hot springs and the Black Mud the springs are formed by deep circulation in granite; the Stone Flower Cave hot springs overflow the hot water on the hillside through the weathered granite fissure and it is formed by shallow circulation of groundwater. Moreover, the YT5-1 spring vent is not clearly observed in the field.