广东雷州半岛玄武岩地下水水文地球化学特征及演化模拟

应用水化学分析软件和水-岩作用模拟软件对雷州半岛的水文地球化学进行了分析和路径模拟。沿东、西2个地下水径流方向从一级台地补给区至二级台地、三级台地排泄区的模拟计算结果表明,地下水可能经历了一系列复杂的水-岩作用,包括石膏、高岭石、钙蒙脱石、伊利石、绿泥石、斜辉石(或透辉石)、针铁矿、赤铁矿的溶解或沉淀及CO2气体的溶解或逸出等地球化学反应。针铁矿、赤铁矿和透辉石的溶解或沉淀量在沿东面地下水径流方向上远小于沿西面方向;针铁矿和赤铁矿只在少量水点发生溶解进入地下水,在大多数水点处于饱和状态而从地下水中析出;CO2气体在大多数取样点发生溶解进入地下水中,其溶解量较大,且随着CO2在水中浓度的变大,其饱和指数也增大,达到饱和后从水中逸出。可见水-岩作用模拟结果有助于揭示研究区地下水化学环境的演化机制。

Hydrogeochemical characteristics and evolution simulation of groundwater in basalts on the Leizhou Peninsula, Guangdong, China

Softwares for hydrochemical analysis and water-rock interaction are used to perform the hydrogeochemical analysis and flow path simulation of groundwater on the Leizhou Peninsula. Simulations of water-rock interactions are made in the directions of groundwater runoffs in the east and west from the recharge area of terrace I to the discharge area of terraces II and III. The research results show that groundwater may undergo a series of water-rock interactions, including dissolution or precipitation of gypsum, kaolinite, Ca-smectite, illite, chlorite, diopside, goethite and hematite and dissolution or escape of carbon dioxide. The quantities of dissolved or precipitated goethite, hematite and diopside are far smaller in the east flow direction than in the west flow direction. Dissolution of goethite and hematite occurs only in a couple of water sample sites, whereas in most water sample sites they are in a saturated state and precipitated from groundwater. Dissolution of carbon dioxide occurs at most water sample sites. The quantity of dissolved carbon dioxide is relatively large and its saturation index increases with increasing concentration of carbon dioxide in the water. The carbon dioxide may escape from water after it reaches saturation. Thus the results of modeling of water-rock interaction are conducive to revealing the evolution mechanism of the groundwater chemical environment in the study area.