摘要
通过水化学法和同位素示踪法对渝东南断裂型碳酸盐岩地热水的地球化学特征及其水资源的形成进行研究。结果表明:郁山断裂以西地热水的水化学类型为Cl-Na型,断裂以东地热水以SO4-Ca·Mg型为主。根据Gibbs图,郁山断裂以西、以东的地热水分别受到蒸发浓缩和岩石风化作用的影响;断裂以西地热水的γNa^+/γCl^-接近1,表明地热水中高浓度的Cl-和Na+主要是源于地层中岩盐的溶解;断裂以东地热水的γ(Ca^2++Mg^2+)/γ(HCO3^-+SO4^2-)接近1,表明地热水中高浓度的Ca^2+和SO4^2-主要来源于地层中膏岩的溶解。地热水的δD和δ^(18)O值分别为-64.7‰^-50‰和-9.17‰^-7.89‰,分布在当地大气降水线两侧,表明补给来源主要为大气降水。地热水水源平均补给高程为1 278 m,这很可能来自附近岩溶中山地区。其热储温度为41~90℃,平均热储温度为66℃;循环深度为1 000~3 500 m,平均值为2 300 m。大气降水到达地表后,在重力(地形)作用下向深部径流,接受地球内部的热传导形成地热水,由西北向东南流动,沿着断裂带上涌,并接受冷水的混入。
Southeast Chongqing is located in the mountain region at the edge of the basin between Wuling mountain and Dalou mountain. Municipally, it falls within two districts and four counties of Chongqing, which are Qianjiang District and Wu Long district, the Shizhu county, the Xiushan county, the Youyang county and the Pengshui county. Paleozoic and Mesozoic sedimentary rocks widely distribute in the area, with lithology dominated by carbonate and clastic rock types. A number of synclines and anticlines expose in a parallel manner in the area where develop many faults.The thermal reservoir studied is mainly composed of dolomites and limestones of the upper & middle Cambrian and the lower Ordovician. It’s overlaid by the stratum layers comprise the upper & middle Ordovician and the lower & middle Silurian, their lithologies are mainly shale, silt stone and inclusion limestone. Below the thermal reservoir is the layer of aquiclude consisting of Gaotai formation of the middle Cambrian, with its lithology dominated by shales. The geochemical characteristics and the formation of the fault-controlled thermal water in carbonate rocks in southeastern Chongqing City were investigated by using the methods of hydrochemistry and isotopic tracer.The result of Gibbs diagram shows that the geochemical characteristics of thermal water in the west and east of the Yushan fault region are affected by evaporation and rock weathering, respectively. The hydrochemical type of the water in the west of Yushan fault region is Cl-Na. Ratio of gNa+/gCl-is close to 1, indicating that high Cl-and Na+concentrations of the thermal water are mainly dominated by the dissolution of halite in the stratum. The hydrochemical facies of the thermal water of east Yushan fault are SO4-Ca·Mg. Ratio of g(Ca2++Mg2+)/g(HCO3^-+ SO4^2-) of the thermal water is nearly equivalent to 1,indicating that the high Ca2+ and SO4^2- concentrations in thermal water are derived from the dissolution of the anhydrite.The δD and δ18O values of the thermal water range from -64.7‰ to -50‰ and from -9.17‰ to -7.89‰, respectively,falling around the local atmospheric precipitation line, which indicates that the recharging source is mainly atmospheric precipitation. The average recharge elevation of thermal water source is 1,278 m, which is likely to come from the recharge nearby karst middle-mountain. The thermal reservoir temperature is from 41 ℃ to 90 ℃ with an average value of 66℃ The circulation depth is in the range of 1,000-3,500 m with an average value of 2,300 m. After the atmospheric precipitation infiltration, it flows into ground under the effect of gravity(topography) and follows with the heat conduction into the upper earth. The thermal water flows from the northwest to the southeast along the fault zone, and is mixed with shallow karst groundwater.
作者
罗丹
杨平恒
王治祥
冉瑜
蒋晶
明晓星
LUO Dan;YANG Pingheng;WANG Zhixiang;RAN Yu;JIANG Jing;MING Xiaoxing(Field Scientific Observation&Research Base of Karst Eco-environments at Nanchuan in Chongqing,Ministry of Natural Resources,School of Geographical Sciences,Southwest University,Chongqing 400715,China;No.208 Hydrogeological Engineering Geological Team of Chongqing Bureau of Geology and Mineral Exploration&Chongqing Exploration and Design Institute of Geological Disaster Prevention Engineering,Chongqing 400700,China)
出处
《中国岩溶》
CAS
CSCD
北大核心
2019年第5期670-681,共12页
Carsologica Sinica
基金
国家自然科学基金项目(41103068)
中央高校基本科研业务费专项(XDJK2018AB002)
关键词
碳酸盐岩地热水
断裂型
地球化学
氢氧同位素
渝东南
carbonate thermal water
fault type
geochemistry
hydrogen and oxygen isotopes
Southeastern Chongqing City
