银川盆地地热水水化学特征及形成机理

Hydrochemical Characteristics and Formation Mechanism of GeothermalWater in Yinchuan Basin

地热能绿色可持续,对于实现“双碳”目标至关重要。银川盆地是典型的寒旱区域,对热能需求巨大。针对银川盆地地热的研究基本集中于估算地热资源量,对地热水的水化学特征及形成机理研究较少。因此以运用水文地球化学、氢氧稳定同位素、放射性同位素(氚和^(14)C)测年和水岩作用模拟等方法分析银川盆地内地热水水化学特征及形成演化机制。研究结果表明银川盆地地热水水化学类型为Cl-Na型和Cl·SO4-Na型。Na^(+)在阳离子中占比最大,Cl^(-)在阴离子中占比最大。岩盐的溶解是Na^(+)的主要来源之一,另一个来源是阳离子交替吸附作用。石膏的溶解是SO_(4)^(2-)主要来源。银川盆地补给区高程为范围在2600~2900 m,平均补给高程为2762.44 m,地热水来源并非大气降水直接补给,而是贺兰山地区高海拔处的大气降水沿贺兰山东麓断裂对银川盆地地下热水进行补给,地热水最老年龄为20750 a,存在亚现代地下水的混合水,补给高程高且距离远。

Geothermal energy is green and sustainable,which is crucial to achieving the“double carbon”goal.The Yinchuan Basin is a typical cold and arid region with a huge demand for heat energy.Previous research on geothermal energy in the Yinchuan Basin mainly focused on estimating the amount of geothermal resources,and there were few studies on the hydro-chemical characteristics and formation mechanism of geothermal water.Therefore,the hydro-geochemistry,hydrogen and oxygen stable isotope,radioisotope(tritium and^(14)C)dating,and water-rock interaction simulation were used to analyze the chemical characteristics and formation and evolution mechanism of geothermal water in the Yinchuan Basin.The research results show that the hydro-chemical types of geothermal water in Yinchuan Basin are Cl-Na type and Cl·SO4-Na type.The main cation of geothermal water is Na+,and the main anion is Cl^(-).Na+comes from the dissolution of rock salt and the alternating adsorption of cations.SO_(4)^(2-)mainly comes from the dissolution of gypsum.The elevation of the recharge area in the Yinchuan Basin ranges from 2600 to 2900 m,with an average recharge elevation of 2762.44 m.The source is that the atmospheric precipitation at high altitudes in the Helan Mountain area recharges the underground hot water in the Yinchuan Basin along the faults and broken zones.The oldest age of geothermal water is 20750 a,there is mixed water of sub-modern groundwater,and the recharge elevation is high and the distance is long.