南京汤泉地下热水化学特征及其指示意义

Hydrogeochemistry of Geothermal Water from the Tangquan in Nanjing and Its Indicating Significance

为确定南京汤泉地区地下热水补给来源,本次对比分析了区内20组不同水样的水化学、氘氧同位素及锶同位素比值的特征。结果表明,汤泉地下热水水化学类型为SO 4-Ca型,热储温度为63~75℃;δD、δ18 O值分别为-42.89‰^-53.21‰、-7.11‰^-8.40‰,均位于当地大气降水线附近,指示其补给来源为雨水,补给高程为321~539 m;Sr同位素比值87 Sr/86 Sr为0.708876~0.709299,表现为碳酸盐岩溶滤水特性。研究认为,地下热水的来源为碳酸盐岩岩溶出露区的大气降水补给,并主要流经碳酸盐岩地层,与浅层冷水和地表水水力联系微弱。

In order to analyze the resource of the geothermal water in Nanjing Tangquan area,20 groups of different water samples were collected to obtain the hydrochemical characteristics and isotopic characteristics of D,18 O and 87 Sr/86 Sr in this area.The research shows that the geothermal water in Tangquan belongs to SO 4-Ca type,and the heat storage temperature is estimated at 63℃to 75℃.The value of theδD andδ18 O in geothermal water are-42.89‰^-53.21‰and-7.11‰^-8.40‰,respectively,and they are located near the local precipitation line.The recharge of this geothermal water is rainwater and the altitude of recharge area is 321 to 539 m.And,the isotope ratio of 87 Sr/86 Sr is 0.708876 to 0.709299,which shows the characteristics of carbonate karst water solution.It is concluded that the origin of geothermal water is the meteoric precipitation from the karst outcropping area,and it mainly flows through the carbonate formation.It has weak hydraulic connection with shallow water and surface water.