Study On Hydrogeochemical Features Of The Thermal Water At Wentang Gorge Anticline In Chongqing, China

The ecological environment and social development is major issue of common concern in the international community today. In the course of the long development of human beings, especially since the industrial revolution, it has made brilliant achievements in transforming the nature and economic development. At the same time, because of the unreasonable exploitation and utilization of natural resources to result in global environmental pollution and ecological destruction, human survival and development is threatened. Protecting the ecological environment and realizing the sustainable development has become urgent and difficult task in the world.As a special water resources, thermal water, because of its energy value, recuperation value and enormous economic value, be widely noticed. Especially, in the21st century with shortage of water resources and the energy crisis, the reasonable exploitation and utilization of thermal water is particularly important. Now, the thermal water is widely exploited and utilized as the tourism resources.Chongqing is economic development center in the west of China, famous "Spy city". There are rich in the geothermal water resources in Chongqing. With social economic growth and the needs for the development of tourism, the thermal water have been massively exploited and utilized. Recently, a series of plans about the development of hot spring, including "ten hot springs’project of five direction" and "exploiting one hundred hot springs in surrounding the city " and "exploiting more hot springs in the flank of the city" and so on, were implemented and Chongqing have been " Chinese hot spring capital ". Now, it is obvious that hot spring resource possessed very important status in tourism development tactic of Chongqing. However, the rapid development of hot spring tourism will put forward higher request to continuance utilize and scientific protecting of the thermal water resource in Chongqing. So, it is important that the thermal water source and reservoir conditions are systematically researched in Chongqing.In this paper, we selected two hot spring points as the research object in Wentang Gorge Anticline. We used hydrochemical and isotopic analytical method to study the thermal water source and hydrochemical feature and the mixing condition of cold water and hot water. According to the data analysis, conclusions can be made as below:(l)The major ions of the thermal water are SO42-and HCO3-and Ca2+and Mg2+. The hydrochemical type is SO42--Ca2+(Mg2+). Total dissolved solids and total hardness and total alkalinity of the thermal water show greatly high value. Another conclusion shows that the major ions are from mineral dissolution of surrounding rock, particularly, from dissolving anhydrite. Moreover, that Sr2+content shows greatly high value may be related to the high content of the background value.(2)According to the fluid-mineral equilibrium analysis of the thermal water samples, we can judge the thermal water not to equilibrate. Maybe the thermal water have mixed underground water. We can use mixture model created by Fournier R.O. and silicon-enthalpy model to calculate the percentage mixed the underground water. The results show that the quantity mixed the underground water is very large. The share mixed the underground water is similar at B1and B2of Bei hot spring and Ql of Qing Muguan hot spring, about76.80%. The share is also similar at Q2and Q3of Qing Muguan hot spring, about87.43%.(3)The study of5D and δ18O shows that the thermal water source is atmosphere precipitation and the recharge elevation is about900m and the recharge area may be the karst outcrops area on the north of the anticline. The δ34S value (31.87%o～33.8%o) of the thermal water is consistent with the δ34S value (32.5%o-35.6%o) of the anhydrite at second phase of Jialingjiang formation in early Trias in Sichuan basin, and the87Sr/86Sr value (0.70803～0.70849) of the thermal water samples is also consistent with the87Sr/86Sr value (0.70724～0.70990) of the celestite at second phase and fourth phase of Jialingjiang formation (Major metallogenic belt of strontium in study area). Comprehensive judgment, the major aquifer is Jialingjiang formation in study area.