苏北盆地老子山地热田成因模式

Genesis Model of Laozishan Geothermal Field,Subei Basin

老子山地热田是苏北盆地的典型地热田之一,阐明其成因模式对于该地热田的进一步开发和热水资源的可持续利用具有一定的指导意义。基于大地热流测试和水文地球化学方法对其进行了系统研究。结果表明:该区大地热流背景值为63.9mW/m2,地热水与浅层地下水和地表水之间在水化学和同位素组成上存在明显差异。经分析,该地热系统属于中低温对流型。其补给区位于距地热田南部约60km处的盱眙—张八岭一带的丘陵地区,热储温度为73～120℃,循环深度为2 350～4 200m,循环周期约为7 800a,热水在区内NNE—SSW向与NW—SE向断裂的交汇处上涌,形成地热田。

Laozishan is a typical geothermal field in Subei Basin.We conducted a systematic study to explore into the genesis mechanism through heat flow measurement and hydrogeochemical investigation,for the purpose of further exploration and sustainable use of the geothermal resources.Results show that the background heat flow is 63.9 mW/m2,and the hydrochemical and isotopic compositions of the thermal water are different from those of the shallow groundwater and surface water.Based on these data,the genesis model of the geothermal field has been postulated to be a low-medium temperature geothermal system of convective type.The recharge area is located in the Zhangbaling to the Xuyi mountain chain with a distance of about 60 km to the south of the geothermal field.The reservoir temperature of the geothermal field has been estimated to be 73-120 ℃,with a water circulation depth of 2 350-4 200 m.The water age is about 7 800 a.The thermal water flows upward in Laozishan area in the intersection zones of the faults striking NNE-SSW and NW-SE.