Hydrochemistry Characteristics and Origin of Geothermal Water in Northeastern Guizhou
Song Xiaoqing;Peng Qin;Duan Qishan;Xia Yanle;No.111 Geological Party,Guizhou Bureau of Geology and Mineral Exploration & Development;Geo-Engineering Investigation Institute of Guizhou Province;Yunnan Chihong Zinc & Germanium Co.Ltd.;
The hydrochemical characteristics of geothermal water and the source of geothermal water have not been systematically carried out in the northeastern Guizhou, and there are problems such as unclear geothermal water sources, recharge areas, runoff and excretion. On the basis of fully understanding the geothermal geological conditions in the northeastern Guizhou,15 groups of geothermal water in the collection area for water chemistry were analyzed, 12 groups of geothermal water hydrogen and oxygen isotopes and 3 pieces of geothermal water carbon isotope data were collected in this study, aimed to firstly obtain the water chemical characteristics and isotopic characteristics of geothermal water in this area, secondly to find the source of geothermal water and thirdly to estimate the recharge elevation, recharge temperature, heat storage temperature, circulation depth, and cold water mixing ratio of geothermal water. The results show that the geothermal water in this area mainly runs from south to north due to the topography and geological structure. The hydrochemical types of geothermal water are mainly HCO_3· SO_4-Ca · Mg,HCO_3-Ca·Mg,HCO_3-Na,SO_4-Ca·Mg and SO_4-Ca types, the beneficial elements are mainly F~- and H_2SiO_3, the geothermal water in the direction of runoff shows a decrease in pH and an increase in TDS,the type of water chemistry changes from bicarbonate to sulfuric acid salt-type water. The results of isotope analysis indicate that the geothermal water supply source in this area is atmospheric precipitation, and the recharge area is Fanjing Mountain area with an altitude of 1 500-2 000 m. The geothermal water age is(6 400-11 570) ±560 a, and the annual average temperature during recharge is 7.0-9.1 ℃. Using silica temperature scale and lg(Q/K)-T method, the heat storage temperature is estimated at 45.0-107.0 ℃, and geothermal water circulation depth of 1 000-3 000 m. By silicon-helium mixed model, the heat storage is estimated before the mixing of geothermal water, showing the maximum temperature at 110-200 ℃.The geothermal water is mixed by the shallow cold water during the ascending process,and the proportion of cold water mixed is 50% to 90%.