Characteristics Of Some Hot Springs And Salt Springs And Formation Of Travertines In Nouthwestern Yunnan

The study area,located in the northwest of Yunnan province and Yanjing in the southeast of Tibet,lies in the geothermal zone of Yunnan-Tibet.A lot of hot springs and salt springs occur in this area where geothermal resources are abundant.The topography in this area varies greatly,the tectonic activities are strong,and the faults are well-developed.The study mainly focuses on the Shangqiaotou hot spring,Xiagei hot spring,Caqugu hot spring,Tianshengqiao hot spring,Dadong hot spring,Adong hot spring,Xilu hot spring Quzika hot spring and Yanjing salt?hot?spring.The study of hot springs,salt spring and the cause of travertine deposition in this area can provide some meaningful guidance for the development and utilization of local hot springs and salt springs resources.The temperature of hot springs in the study area ranges from 39 to 70 ?,pH from 5.9 to 7.5,and TDS from 258 mg/L to 3430mg/L.The temperature of the Yanjing salt springs ranges from 21 ? to 49.5 ?,pH from 5.9 to 6.8,TDS from 26 to 110.5 g/L.The hydrochemical type of the Shangqiaotou hot spring,Xiagei hot spring,Caqugu hot spring,Tianshengqiao hot spring,Dadong hot spring,Adong hot spring,Xilu hot spring,Quzika hot spring and Yan jing salt spring are HCO3?SO4-Ca?Mg,HCO₃^-Na?Ca,HCO₃^-Na?Mg,HCO₃^-Ca?Mg,HCO3?SO4-Ca?Mg,SO4?HCO₃^-Na?Ca,SO4?Cl-Na?Ca,HCO₃^-Na and Cl-Na,respectively.In the study area the values of ?2H of the water samples range from-147.5‰ to-112.9‰,?18O ranges from-16.8‰ to-12.3‰,showing more negative values.Most water samples appear different degree of “18O drift” phenomenon.The hydrogen and oxygen stable isotope data indicate that the hot springs and salt springs are of meteoric origin.By analysing ?2H and ?18O,the elevations of recharge area are estimated as 3000⁴516m,The temperature of recharge area is estimated as-3.9 to 5.2 ?;By using 226Ra-222 Rn method,the ages of underground hot water are estimated as 316 a to 1963 a.By using geothermometer methods,the thermal reservoir temperature is estimated as 59.8²02.2 ?;By using circulating depth formulas,the circulation depths are estimated as 1980 to 4504.5m;By using mixture of cold and hot water method,the mixture ratios of cold water are estimated as 18% to 82%.Adong hot spring exposes in the layer of Triassic volcanic clastic rock,under the control of the Deqin-Zhongdian-Daju fault zone.The hot spring circulates deeply along water channel after receiving the recharge of atmospheric water,and then the water forms a hot spring on the ground surface after heating by terrestrial heat flow.And other hot springs and salt spring also are deep circular springs.By comparing the hydrochemical characteristics of the travertine deposition of hot springs and the non-travertine deposition hot springs,this paper find that the travertine deposition requires higher content of Ca²⁺ and HCO₃^-as the material basis;The Ca²⁺ / HCO₃^-value should be greater than,or equal to 0.1;the percentage of milligramme equivalent of Ca²⁺ and HCO₃^-in the main cation and anion should be greater than 25%,The saturation index of Calcite,Aragonite and Dolomite of the springs should be greater than 0,or close to 0,which is beneficial for the deposition of calcium carbonate.