海南岛温泉特征与地下热水成因

Characteristics of Thermal Springs and Genesis of Thermal Underground Waters in Hainan Island

通过对海南岛区域地质构造、岩浆岩与温泉分布的关系，以及温泉水化学和同位素分析，总结该区温泉的属性特征，阐明地下热水的成因。温泉在地势较低的琼西北和琼东南呈对称性条带状分布。水质类型大多为低矿化的重碳酸盐型，呈碱性，含较高的氟和硅；第四系滨海区受海水影响则表现为氯化钠型。温泉的氢、氧、氦同位素及气体组分揭示地下热水起源于大气降水，大气降水在地壳浅部循环过程中被围岩加热成地下热水。地热资源为中低温对流型地热系统，热储温度为59．5～161．2℃，平均128．5℃，是由偏高的区域热流在深部供热的，与岩浆作用无关。地下热水的出露受区内NE、EW向深大断裂控制。

The regional structural geology, igneous rocks and spatial relationships among the springs, as well as the springs＇ hydrochemistry and isotope datum were analyzed. The characteristics of thermal springs in Hainan Island could well be concluded by this study, and formation of thermal underground water can be detected. The thermal springs distribute over northwest and southeast areas which are located at lower altitude. The type of water is mainly HCO3 dominant, and slightly alkaline, high fluorine and silica. However, those from Quaternary beachfront region are the type of NaCl dominant because of seawater influence. Data on hydrogen, oxygen, helium isotopes and gas chemical composition showed that the underground thermal water was originated from local precipitation, then this precipitation was heated by the surrounding rocks when it cycled in earth＇s upper crust and warmed to hot underground water finally. Geothermal source belongs to a low - medium temperature convectional geothermal system, and equilibrium temperature of the geothermal reserve in the range of 59.5 - 161.2℃ with the average temperature of 128.5℃. The heat energy is not influenced by magmatic activities but related to the higher regional geothermal flow in deeper region. The out-crops of thermal underground water are controlled by the regional NE, EW trending faults.