| The Tianshengqiao and Xiagei hot springs are located in Shangrila County of the Tibetan Autonomous Prefecture of Diqing in Yunnan Province where geothermal resources are rich. The hot springs are located in the high mountain fault basin, the spring went expose to the natural arch fault zone of the northwest of the Gezan river fracture of the upper Triassic Hagong Group.The rocks are mainly limestone. Research on hot spring and travertine deposits is improtant for understanding terrestrial water cycle.The water temperature of the Tianshengqiao hot spring is between 56.9℃ and 54.5℃ respectively, and the chemical type of water is of HCO3-Ca?Na type and HCO3-Na?Ca type. The water temperature of the Xiagei hot spring varies from 41.4℃ to 63.1℃, and the chemical type of water is of HCO3-Na type or HCO3-Na?Ca type.Two spring vents are mildly acidic water and brackish water. Cation is mainly Na+, Ca2+, anion is mainly HCO3-. F-, Li, Sr, metasilicic acid and boric acid contents are high in the hot water. The water belongs to the medical mineral water.In this paper, based on the geothermal geological conditions of the Shangrila basin, hydrochemistry compositions and isotope method are used as the main research methods. It is found that the two hot springs belong to middle-low temperature convection system. The conceptual model of occurrence is similar. The area of the southeast of Cina is the two hot springs recharge area, the elevation is about 3697 m and 3812 m respectively, and the temperature is about 1.7℃. The precipitation of the recharge area begins to infiltrate through the Tianshengqiao deep faults of good permeability by water pressure drived. Because of the geothermal gradient, the groundwater water temperature is gradually heated by surrounding rocks with the increase of circulation depth. The underground heat storage temperature is up to about 96 ℃ and 160 ℃ respectively at 3518 m and 3980 m depth. Subsequently the underground water rises through fracture interchange. When the underground hot water rises to or close to the surface, it mixes with shallow cold water, and the proportion of cold water are 52% and 72% respectively, Then the mixed water exposes in the form of Tianshengqiao hot springs ang Xiagei hot springs with temperature of 56℃ and 41.4℃ to 63.1℃ respectively. The groundwater residence time is about 16 a and 50 a. In the process of geothermal groundwater to rise to carry a large amount of CO2, which comes from underground mantle, carbonate rocks dissolve, and 69.5% CO2 of the Tianshengqiao hot springs and 73.8% ~ 73.8% CO2 of the Xiagei hot springs mainly comes from deep underground.The Tianshengqiao and Xiagei hot spring deposit travertine. The mainly forms are travertine ridge, travertine cone and travertine wall. Travertine mainly are pale, and the weathering phenomenon is serious. Through analysising travertine cause of the two hot springs, it is found that high contents of HCO3-, Ca2+, CO2 and CO2 partial pressure are the main condition for the travertine deposition. The formation process of travertine is roughly divided into three stages: initial stage, growth stage and closed stage. Currently the travertine is at the stage from the closed or to the closing stage of transition. |
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