黔东北地区地热水化学特征及起源

目前在黔东北地区未系统地开展过地热水水文地球化学特征以及地热水来源方面的研究，存在地热水来源、补给区域、径流和排泄等特征不清等问题.在充分了解黔东北地热地质条件的基础上，采集区内15组地热水进行水化学全分析、收集12组地热水氢氧同位素和3组地热水碳同位素数据，得到了该区地热水的水化学特征和同位素特征，分析出地热水的补给来源，估算了地热水的补给高程、补给温度、热储温度、循环深度以及冷水混入比例.结果表明，受地形地貌及地质构造的影响，该区地热水总体由南向北径流，水化学类型主要为HCO₃·SO₄-Ca·Mg、HCO₃-Ca·Mg、HCO₃-Na、SO₄-Ca·Mg及SO₄-Ca型，有益元素主要有F-和H₂SiO₃，沿径流方向地热水呈现pH降低、TDS增加的趋势，水化学类型则由重碳酸盐型水变为硫酸盐型水.同位素分析结果表明，该区地热水补给源为大气降水，补给区为海拔1 500~2 000 m的梵净山地区，地热水年龄为（6 400~11 570）±560 a，补给时的年平均气温为7.0~9.1℃；选用二氧化硅温标及lg（Q/K）-T法估算热储温度为45.0~107.0℃，地热水循环深度为1 000~3 000 m；硅-焓混合模型估算地热水混合前的热储温度极大值为110~200℃，地热水在上升过程中受浅部冷水混合，冷水混入比例为50%~90%. 

Hydrochemistry Characteristics and Origin of Geothermal Water in Northeastern Guizhou

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 HCO₃·SO₄-Ca·Mg, HCO₃-Ca·Mg, HCO₃-Na, SO₄-Ca·Mg and SO₄-Ca types, the beneficial elements are mainly F- and H₂SiO₃, 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%.