河北何家庄流体观测井水文地球化学特征分析

Geochemical Characteristics of Fluid from Hejiazhuang Observation Well in Hebei Province

应力、应变或地震活动会打破地壳中流体原有的水-岩平衡状态,引起地下流体化学组分和同位素的变化。根据河北何家庄流体观测井氢氧同位素和离子化学组分测试结果,分析了该井的地球化学特征及与构造活动的关系。由氢氧同位素结果及高程效应,判定井水来源主要为大气降水,大气降水沿断裂裂隙渗入,深循环后温度增加,经溶滤作用等形成热水;按照舒卡列夫分类法,何家庄井水为Cl-Na.Ca型。受2015年9月14日昌黎M4.2地震的影响,区域应力变化使井孔断裂岩石裂隙增大,深部热水上涌,引起何家庄井水离子组分和氢氧同位素组成等发生变化。研究结果表明,对何家庄井流体地球化学特征进行分析,可以为井孔附近断裂构造活动和地震前兆异常分析提供地球化学依据。

The change of stress caused by fault activity will break the balance of water-rock reaction of groundwater,which will lead to the change of hydro-chemical type and hydrogen oxygen isotopic composition.In this paper,we analyzed ion chemical composition and hydrogen oxygen isotope of fluid from Hejiazhuang observation well,and studied the geochemical characteristics of the well and the relationship with tectonic activity.Firstly,based on the results of hydrogen and oxygen isotopes and elevation effect,we determined that the main source of well water is atmospheric precipitation,which infiltrates along fracture fissures,increases temperature after deep circulation,and forms hot water through dissolution and filtration.Then with accordance to Shukarev classification,the water type of Hejiazhuang well is classified into Cl-Na.Ca type,which is under the influence of Changli M4.2 earthquake on September 14,2015.We believed that the regional stress change increased the rock fracture in the fracture zone of the borehole,and the deep hot water upwelling,resulting in the change of ion composition and hydrogen oxygen isotope composition of the well water in Hejiazhuang.The results show that the geochemical characteristics of the fluids in Hejiazhuang well can provide geochemical basis for the analysis of the fault structural activities and the earthquake precursor anomalies near the fluid observation well.