鄂尔多斯盆地南区环河组地下水水岩作用研究

Geochemical modeling of Huanhe water-bearing layers in south Ordos Basin

文中以揭示鄂尔多斯盆地南区白垩系环河组地下水水化学场的形成机理为主要研究目的。在了解鄂尔多斯盆地水文地质条件的基础上,分析了环河组地下水水化学演化特征,应用Phreeqc软件对其进行了水-岩作用的地球化学模拟,定量分析研究了该区地下水的演化过程、形成机理,并进一步分析了南区环河组地下水的补、径、排关系。得出结论为:在水流模拟路径上主要发生了石膏、岩盐、斜长石、钾云母或钾长石的溶解反应和阳离子交替吸附作用,导致地下水的TDS不断增大;其间,受总排泄带位置及东西两侧径流的影响,使水化学演化方向、径流方向产生朝向总排泄带的"向心"偏转,因此,环河组大体上以马莲河入泾河汇入口附近为中心,形成半个向心椭圆状的地下水流动系统。该结论对盆地南区地下水流动系统的划分、边界界定,具有特殊意义。

The purpose of the study is to study the evolution meehanism of geochemical field in groundwater of Hanhe water - bearing layers in south Ordos Basin. Based on the understanding of South Ordos Basinhydro - geological condition, the chemical evolution characters of groundwater of Huanhe bearing layer were analyzed. Phreeqe softwares were used to perform a geochemical modeling for water - rock interaction, and analyze quantitatively the evolution process, forming mechanism of the local groundwater, further to analyze the interaction of change, runoff and dischange of groundwater in Huanhe water bearing layer. Some conclusions were summarized, including dissolution reactions of gypsum, halite, plagioelase, k -mica, K -feldspar and cation exchange, which result an constant increase to TDS of groundwater in modeling direction ; the direction of aqueous chemical evolution and groundwater runoff are declined to the centre of main discharge zone with the influence of final discharge zone site and east - west runoff. Thus, the discharge zone site is close to the entrance in which the Malian River flows to Jing River, and in which form the centre of groundwater flow system of Huanhe. These conclusions are provide with significance to divide a groundwater flow system of the south Ordos basin and delimit boundaries.