宜春鼻田和温汤地热水氢氧同位素特征研究

Hydrogen and oxygen isotope characteristics of geothermal waters at Bitian and Wentang in Yichun city

采集了鼻田和温汤地热水以及袁河水,分别测试了其氢氧同位素组成、酸碱度(pH)、电导率(EC)、溶解性总固体(TDS)和HCO 3-浓度。结果表明,地热水TDS较小,呈弱碱性,导电率较小。地热水的δD值和δ^(18)O值的变化范围分别为(-45.95‰~36.93‰)和(-7.54‰~4.36‰),比河水的δD值(-34.11‰~31.04‰)和δ^(18)O值(-5.91‰~5.32‰)变化范围大。地热水的氢氧同位素分布与宜春地区大气降水线较一致。表明地热水的补给来源为大气降水,补给高程范围在370 m-761 m。结合该区水文地质条件,明确了地热的形成机理,即:地热水源自大气降水,是通过入渗进行补给,并沿断裂深部循环加温后所形成。地下热水在上升过程中,受花岗岩围岩具有阻水性的影响,其沿裂隙带上升并与浅部风化裂隙水混合后扩散。

Bitian and Wentang geothermal water and Yuanhe river water samples were collected to measuretheir hydrogen and oxygen isotope composition,pH,EC,TDS and HCO 3-concentration.The results shows that the geothermal water belongs to low temperature geothermal field with low TDS,weak alkalinity and low conductivity.TheδD andδ^(18)O values of geothermal water,varying from-45.95‰to-36.93‰and-7.54‰~-4.36‰,has larger variations than river water(δD:-34.11‰~-31.04‰,δ^(18)O:-5.91‰~-5.32‰).The consistent isotopic composition of geothermal water and meteoric water line in Yichun indicates that the recharge source of geothermal water is atmospheric precipitation.The recharge altitude ranges from 370 to 761 m.Combined with the hydrogeological conditions of this area,the formation mechanism of geothermal is defined,that is,geothermal water originates from atmospheric precipitation,is recharged through infiltration,and is formed after cyclic heating along the deep fault.Influenced by the water resistance of the granite rock,the underground hot water rises along the fracture zone and diffuses after mixing with the shallow weathered fracture water.