Characteristics Of The Hot Springs And Salt Springs In The Yunlong District Of Yunnan

The Yunlong district is located in the west of Yunnan province. The district is affected by the collision of the Indian Ocean plate and the Eurasian plate, and belongs to the Yunnan-Tibet geothermal belt. The Yunlong area is situated in the Lanping basin which is in the northern Qiangtang-western Yunnan’s salt metallogenic belt. There are many hot springs and salt springs in the study area. Through the analysis of geological characteristics and springs’ hydrochemical characteristics, we can put forward the genetic models of the hot springs and calculate the geothermal resources in order to provide a basis for the development and utilization of the geothermal. By analyzing the occurrence of the salt springs, we can give suggestions to looking for potassium and utilizing potassium resources.Hydrochemical investigations show that the temperature of Caojian Xiazaotang hot spring, Shifang hot spring, Shicheng hot spring and Wenxing hot spring ranges from 45.1℃ to 68℃, p H is between 6.38 and 8.65, Eh is-106-45 m V, and TDS from 0.251 g/L to 7.85 g/L. In addition to the fresh hot spring of Caojian Xiazaotang, the other three are brackish hot springs. The temperature of the Nuodengjing salt spring, Longquan salt spring, Shijing salt spring and Shundangjing salt spring varies between 16.3℃ and 21.7℃, p H between 6.35 and 7.6, Eh between-5 m V and 42 m V and TDS between 19.3 g/L and 137 g/L. The water samples are divided into three hydrochemical types: the Shicheng hot spring and the four salt springs are of Cl-Na type, the Caojian Xiazaotang and Shifang hot springs are of HCO₃-Na type and the Wenxing hot spring is of SO₄·Cl-Na·Ca type. The metaboric acid content is higher in the springs, which ranges from 0.74 mg/L to 24.3 mg/L, the content of F- from 0.25 mg/L to 17.3 mg/L and the metasilicic acid from 10.4 mg/L to 92.3 mg/L. Most of the springs in the study area are of medicinal value and are suitable for bath spa. The content of free carbon dioxide in the springs varies between 37.4 mg/L and 286 mg/L, which is negatively related to p H and positively related to Eh. Carbon dioxide content of the springs occurring in the red sandstone or near the faults is higher（110-286 mg/L）. δ¹³C in the carbon dioxide is about-8‰, indicating that the gas is derived from the mantle.The isotope analysis shows that the hot springs are meteoric in origin and receive recharge from precipitation in mountain areas with elevation of about 1886-3268.98 m. The range of the residence time of the thermal groundwaters is estimated to be 10-316 years. By method of geothermometers, we can calculate the temperature of the geothermal reservoirs（83.4℃-104.6℃）. As a result, the research area belongs to the low-medium temperature geothermal system of convection type. The hot springs have experienced the deep circulation and the circulation depth of the geothermal systems ranges from 1714 m to 2245.3 m. The natural heat quantity of the hot springs ranges between 4.3×10¹¹ J/a and 5.5×10¹³ J/a（14.8-1874.1 t/a of standard coal）. Of the hot springs, the Caojian Xiaozaotang is valuable to the development and utilization.The salt springs are meteoric in origin and recharge elevation varies from 3083.08 m to 3294.57 m. The ion characteristic coefficient of γNa/γCl is about 1 and Br×103/Cl is 0.135-0.392. In addition, the springs’ temperatures are low and dynamic characteristics change obviously with the seasons. Conclusion can be drawn that the salt springs form after halites are leached in the red rocks during a shallow circulation. The levels of abnormal potassium are secondary in the Nuodengjing salt spring, Longquan salt spring, Shijing salt spring, Shundangjing salt spring, Shicheng hot spring and Wenxing hot spring in the study area. K contents of the four salt springs and Shicheng hot spring are higher, which range from 52.8 mg/L to 213 mg/L. While the content of K⁺ in the Wenxing hot spring is only 6.91 mg/L. As a result, the four salt springs and Shicheng hot spring have a better prospect of potash resources. However the Wenxing hot spring does not have prospect for potassium.