基于水文地球化学特征的辽宁丹东地区地热水成因模式研究

辽宁丹东地区地热资源丰富,阐明其地热田的成因模式对于区域热水资源的可持续开发利用具有重要意义。以区内北汤、东汤、五龙背地热田为研究对象,进行水化学和同位素分析。结果表明,北汤、东汤、五龙背地热水的水化学类型分别为SO₄·Cl-Na·Ca型、HCO₃·SO₄-Na型、 HCO₃-Na·Ca、HCO₃·SO₄-Na和HCO₃·Cl-Na型。研究区的热水来源为大气降水,北汤、东汤地热田的补给高程分别为678 m和376 m。根据¹⁴C测年方法,得出北汤、东汤和五龙背地热田地热水年龄分别为2 000~3 300 a B.P.、2 200~7 200 a B.P.和700~2 900 a B.P.。根据二氧化硅地温计和lg(Q/K)方法,北汤、东汤和五龙背地热田的热储温度分别为92 ℃、120 ℃和100~101 ℃,相应的地热水循环深度分别为1 900 m、3 000 m和800~1 800 m。地热水接收大气降水入渗补给,经断裂带深循环加热,于NNE和NW向两组断裂交汇处上涌进入浅部含水层或出露地表成泉,属中低温对流型地热系统。

Genesis Model of Geothermal Water in Dandong Area of Liaoning Province Based on Hydrogeochemical Characteristics

Geothermal resources are abundant in Dandong. It is of great significance to establish the genesis model of the geothermal fields for sustainable utilization and further development. The geothermal fields of Bei-tang, Dongtang and Wulongbei were investigated for hydrochemical and isotopic analysis. The results show that the hydrochemical types of Beitang, Dongtang and Wulongbei geothermal water are SO₄·Cl-Na·Ca, HCO₃·SO₄-Na and HCO₃-Na·Ca, HCO₃·SO₄-Na and HCO₃·Cl-Na, respectively. The source of the thermal water is atmospheric precipitation. The recharge elevations of Beitang and Dongtang geothermal fields are 678 and 376 m, respectively. According to ¹⁴C dating methods, the ages of the thermal waters in Beitang, Dongtang and Wulongbei geothermal fields are 2,000-3,300 and 2,200-7,200 and 700-2,900 a B.P., respectively. The reservoir temperatures of Beitang, Dongtang and Wulongbei geothermal fields are predicted to be 92, 120, and 100-101 ℃, respectively according to the silica and lg(Q/K) geothermometer. The thermal water circulation depth of Beitang, Dongtang and Wulongbei geothermal fields are ca. 1,900, 3,000 and 800-1,800 m, respectively. The thermal water is heated up during deep circulation through the fault zone, and then upwelled into shallow aquifers or outcrops as springs at the intersection of NNE and NW trending faults, which belong to low to medium temperature geothermal system of convective type.