安徽大别山区温泉的水化学与同位素特征及成因

安徽大别山区位于扬子板块和中朝板块之间的碰撞造山带东部, 南东侧以池-太断裂为界, 北西侧止于金寨深断裂, 向东至庐江东汤池。对大别山区5个温泉, 即太湖县汤泉乡汤湾温泉(AH2)、岳西县温泉镇温泉(AH6)、岳西县菖蒲镇溪沸温泉(AH7)、庐江县东汤池温泉(AH11)和舒城县西汤池温泉(AH12)进行调查和分析。深大断裂和与之平行或斜交的小型断裂控制着大别山区温泉的出露, 地下热储带分布于花岗岩和变质花岗岩中。温泉水温为40~70℃, pH值为7~8.8, 均为中低温、弱碱性温泉。温泉氢氧稳定同位素组成表明, 大别山区温泉的补给水源为大气降水, 并具有轻微的18O漂移现象。利用同位素高程效应公式估算温泉补给区高程为950~1300 m, 补给区平均温度约为8.2℃。地下水在大别山区接受大气降水入渗补给, 经历深循环受到来自深部热源的加热之后, 沿断裂带或破碎带上升, 在山谷、河谷的低处出露形成温泉。估算的热储温度为80~120℃, 热水循环深度为1400~1800 m。结合硅焓方程法和实地调查, 认为AH2和AH7不存在冷热水混合, AH6、AH11和AH12若继续扩大开采, 不排除会发现热水与浅部冷水的混合。

Hydrochemical and isotopic characteristics and formation of the hot spring in the Dabie Mountain area,Anhui Province

The Dabie Mountain area in Anhui is located in the eastern part of the collision orogenic belt between the Yangtze Plate and China-Korea continental Plate.The southeast side is bounded by the Chi-Tai fault, the northwest side ends by the Jinzhai deep fault, and east side to East Tangchi in the Lujiang.Five hot springs in the Dabie Mountain area including the Tangwan hot spring(AH2)in Tangquan Township of Taihu County, Wenquan Town hot spring(AH6)in Yuexi County, Xifei hot spring(AH7)in Changpu Town of Yuexi County, East Tangchi hot spring(AH11)in Lujiang County and West Tangchi hot spring(AH12)in Shucheng County are investigated.Deep and large faults and small parallel or oblique faults control the occurrence of the hot springs in the study area, and underground heat storage zones exist in the granite and metamorphism granite.The water temperature of hot springs in the study area ranges from 40~64℃, and the pH value, from 7 to 8.8.The hot springs are of medium-low temperature and are weakly alkaline hot springs.The stable isotope compositions of hydrogen and oxygen of the hot springs indicates that the hot springs in the Dabie Mountains area are of meteoric origin and have a slight 18O shift.Based on altitude effect, the elevations of recharge areas of the hot springs are estimated to be about 600~900 m, and the average temperature of the recharge areas is about 8.2℃.After receiving recharge from infiltration of precipitation in the Dabie Mountain area, groundwater is heated by heat flow from below during deep circulation, then rises to the surface along fault zones or fracture zones, and emerges in the form of hot springs in the lower parts of valleys and river valleys.The estimated temperatures of the geothermal reservoirs are 80~120℃, and the circulation depth of hot water, 1400~1800 m.The results with silicon enthalpy equation method and field investigation, indicate that there is no mixing of hot and cold water in hot springs AH2 and AH7.If hot springs AH6, AH11 and AH12 are exploited continually, mixing of hot water and shallow cold water will be expected.