湖北京山地区地热田地球化学特征及热源分析

GEOCHEMICAL CHARACTERISTICS AND HEAT SOURCE OF THE GEOTHERMAL FIELD IN JINGSHAN AREA,HUBEI PROVINCE

依据采自京山县地热田JR5JR9井水化学特征和同位素分析,确定其补给源和径流路径;JR7井30年来水化学的变化与冷热水混和、地热流体温度降低有关;通过对井JR5JR8选择钾、镁、二氧化硅地球化学温标估算热储温度,SiO2温标与钾、镁温标评价结果基本一致,地热田热动力平衡温度为99-108℃,热储深度约在744 m;同位素示踪研究表明地热田补给源来自大气降水,补给高程应在800 m以上;根据氚的半衰期估算,其径流时间4060年;从区域地质条件分析,地热流体的补给区位于距地热田西北约60 km的大洪山区,区内玄武岩流活动和喷发给地热田带来的了大量的热能;京山深大断裂为地下水提供了运移通道,经深循环加热后,在汤堰畈附近富集,形成地热田。

Based on chemical features and isotope analyses of water from JR5 to JR9 wells in the geothermal field of Jingshan County,the authors determined the replenishment fountainhead and path of the water.Chemical change of water in JR7 well in the past 30 years has been related to mixture of hot and cool water and cooling of terrestrial heat liquid.Geochemical thermometric scales of K,Mg and silicon dioxide were chosen to estimate temperature of the geothermal reservoir,and the results of the SiO2 thermometric scale are almost consistent with the K and Mg thermometric scale,with the thermodynamic equilibrium temperature of the geothermal field being 99～108 ℃,and the depth of the thermal reservoir being 744 meters.Researches on isotope tracing indicate that the recharge source of the geothermal field is meteoric water,and the recharge height should be over 800 m.Calculation of the half-life of tritium shows that the duration of the runoff should be 40～60 years.An analysis of regional geological conditions reveals that the replenishment area of the geothermal fluid is located in Dahong Mountain area about 60 kilometers northwest of the geothermal field,and the activity and eruption of basalts have brought a mass of heat energy.In addition,Jingshan area has a deep fracture,which could provide the pathway for groundwater;the water is heated through deep circulation and then concentrated near Tangyangfan,thus forming the geothermal field.