贺兰山东麓断裂地下水水文地球化学特征
王晓涛,丁风和,张燕霞,李新艳,贺嘉伟

(宁夏回族自治区地震局,宁夏 银川 750001)

地下水; 贺兰山东麓断裂; 水文地球化学; 氢氧同位素; 微量元素

Hydrogeochemical Characteristics of the Groundwater in the Eastern Piedmont Fault of the Helan Mountains
WANG Xiaotao,DING Fenghe,ZHANG Yanxia,LI Xinyan,HE Jiawei

(Earthquake Agency of Ningxia Hui Autonomous Region,Yinchuan 750001,Ningxia,China)

groundwater; the Eastern Piedmont Fault of the Helan Mountains; hydrogeochemistry; hydrogen and oxygen isotopes; trace elements

DOI: 10.20015/j.cnki.ISSN1000-0666.2023.0002

备注

以贺兰山东麓断裂带内地下水为研究对象,运用Piper三线图、离子比值等方法对研究区内丰水期与枯水期地下水的水化学特征进行分析,探讨了断裂与水化学组成及地震活动的关系,并建立贺兰山东麓地区地下水成因模型。结果表明:①区域地下水总体偏弱碱性,阳离子以Ca2+和Na+为主,阴离子以HCO-3和SO2-4为主; ②区域地下水主要受大气降水补给,补给高程为1.07～2.04 km。Na-K-Mg三角图显示,研究区地下水为“未成熟水”。绝大多数水样的矿物饱和指数SI<0,表明区域地下水中各个离子含量大体处于未饱和状态。利用温标法估算该区域地下水的热储温度为74.6 ℃～114.1 ℃,循环深度为1.7～2.8 km; ③地下水样中的Sr、Ba、Li等微量元素富集因子EF>1,富集程度高,其余大部分微量元素含量较低,说明当地地下水为未成熟水,矿化度低,水岩反应程度不强。④研究区地下水出露点主要沿贺兰山东麓断裂展布,水温、矿化度、矿物饱和指数及水循环深度呈北高南低的分布特征,水化学组分高值区内小震活动频度高但强度弱。⑤研究区地下水在附近山区接受大气降水入渗补给,在地下循环过程中被大地热流加热,期间与围岩发生一系列水岩反应,后沿断裂上升以温泉的形式出露地表。
In this study,10 groundwater samples were collected in the Eastern Piedmont Fault of the Helan Mountains to investigate the hydrogeochemical characteristics during the flood and dry season by various methods,such as Piper trilinear diagrams and ion ratios.We also discussed how the Eastern Piedmont Fault of the Helan Mountains was related with the chemical composition of the groundwater and the earthquake activity. We further built a model illustrating the genesis of the groundwater in this area.The results show that:① The groundwater is generally alkaline in this area.The main cations in groundwater samples are Ca2+and Na+,while the main anions are HCO-3 and SO2-4.② Hydrogen and oxygen isotopes indicate that precipitation is the main source of recharge for groundwater in the study area,and the recharge height is between 1.07 km and 2.04 km.Almost all groundwater in the study area is “immature water” with a weak degree of water-rock reaction.The mineral saturation index in most water samples is less than 0,indicating that the content of each ion in the regional groundwater is generally in an unsaturated state.The geothermal reservoir temperature calculated is 74.6 ℃—114.1 ℃,and the circulation depth ranges from 1.8 km to 2.7 km.③ Most of the trace elements enrichment factors(EF)are less than 1,indicating that the groundwater is “immature”with low mineralization.The degree of water-rock reaction was relatively weak.④ Water temperature,mineralization,mineral saturation index and water circulation depth is high in the north part and low in the south part.The small earthquakes's activity has a high frequency but weak intensity in high value zone of hydrochemical components.⑤ Groundwater in the study area is recharged by infiltration of atmospheric precipitation in the nearby mountains,and the groundwater during subsurface circulation is heated by the Earth's heat flow.The groundwater reacts with the surrounding rock and eventually rises along the fracture to the surface as hot springs.
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