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摘要:
南京汤泉地区地下热水资源丰富，阐明其补给来源及成因模式，对于地下热水的科学开发意义重大。采用水化学及同位素地球化学分析方法对其进行了系统研究。结果表明，研究区地下热水与浅层冷水水化学组成差异明显，热储温度为63~75℃，循环深度为1.8~2.3 km。大气降水入渗是地下热水的补给来源，补给高程范围为321~539 m；循环周期为2046~6474 a；地下热水上涌过程中会混入比例为4%~26%的浅部岩溶冷水。经分析，该地热系统成因上属于中低温对流型，补给区主要为老山复背斜构造内的碳酸盐岩裸露区，依靠区域大地热流供热，热储层主要为上震旦统白云岩，盖层为寒武系、白垩系及第四系，地下热水经深循环沿NEE向与NW向断裂交会通道向上运移，并与浅部冷水发生混合，形成本区的地热异常。
Abstract:Nanjing Tangquan is rich in geothermal water.It is of great significance for the sustainable use of geothermal water to reveal its supply source and genesis mechanism.The method of hydrochemistry and isotope geochemistry was taken to make the systematic study.The chemical composition of geothermal water is different from that of shallow cold water.The thermal reservoir temperature has been estimated to be 63~75℃, with a water circulation depth of 1.8~2.3 km.The geothermal fluid origins from the rainfall, and the altitude of recharge area is 321~539 m.The water age is 2046~6474 a, with shallow karst cold water mixed while upwelling, and the mixing ratio is 4%~26%.Based on these analysis, a genesis model of the study area has been postulated to be a low-medium temperature geothermal system of a convective type.It receives the precipitation from the karst outcropping area in Laoshan complex anticline, and it is gradually heated by the normal heat flow during circulating.The thermal reservoir is originally the Upper Sinian series dolomite.The cap rocks are mainly Cambrian, Cretaceous and Quaternary strata.The geothermal water flows upward in the intersection zones of the NEE- and NW-striking faults along deep circulation, and mixing with cold water in shallow, forming the geothermal anomalies.
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Key words:
- geothermal water /
- hydrogeochemistry /
- origin of geothermal water /
- genesis model /
- Nanjing
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表 1 水化学及同位素测试数据
Table 1. The data of hydrochemistry and isotopes
水样编号 温度/℃ 离子含量/(mg·L-1) 同位素值/‰ K+ Na+ Ca2+ Mg2+ Cl- HCO3- SO42- H2SiO3 δD δ18O H1 37.0 6.77 12.4 682.0 102.0 5.55 301 1789 55.1 -54.9 -8.83 H2 46.0 6.96 12.2 566.0 108.0 6.93 299 1523 60.2 -56.2 -8.71 H3 22.0 3.60 11.8 174.0 33.9 20.8 134 444 20.3 -49.9 -8.00 H4 32.4 4.92 12.0 464.0 84.4 6.93 332 1178 48.0 -54.3 -8.62 H5 35.5 5.31 13.2 457.0 88.4 10.4 332 1180 46.8 -54.2 -8.74 H6 41.4 6.38 12.6 541.0 98.9 6.93 314 1489 54.5 -55.8 -9.27 C1 15.8 4.79 21.7 368.0 71.2 41.6 343 904 32.6 -46.6 -7.85 C2 15.2 0.81 17.4 138.0 35.0 24.3 270 230 32.0 -46.8 -7.98 C3 14.8 61.80 50.5 66.5 21.3 54.1 339 75.5 30.0 -43.9 -7.58 C4 16.2 0.64 98.9 52.8 10.8 69.3 257 49.9 27.0 -46.0 -7.16 C5 14.6 1.63 21.7 58.6 22.1 41.6 157 62.9 31.9 -44.2 -7.69 C6 16.5 2.93 63.6 126 32.7 70.7 389 139 35.3 -44.4 -7.47 C7 16.5 2.05 67.3 92.8 19.4 54.1 299 115 23.7 -42.9 -7.11 C8 16.2 4.10 46.6 84.5 23.0 61.0 213 96.4 36.2 -45.0 -7.14 C9 15.6 3.39 66.4 57.2 20.5 61.0 163 69.8 42.4 -44.1 -7.30 
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表 2 二氧化硅地热温标计算结果
Table 2. The calculation results of SiO2 geothermometer
℃ 样品编号 井口温度 无定形硅 α-方石英 β-方石英 玉髓 Fournier, 1977 H1 37.0 -15 50 3 70 H2 46.0 -12 54 7 75 H3 22.0 -49 10 -33 27 H4 32.4 -20 44 -2 64 H5 35.5 -21 43 -3 63 H6 41.4 -16 50 3 70
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表 3 地下热水循环深度
Table 3. Depth of geothermal water circulation
样品编号 深度/m 备注 H1 2117 H2 2292 H3 417 混入冷水较多，计算结果偏低 H4 1854 H5 1807 H6 2096
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表 4 汤泉地区地下热水补给高程计算结果
Table 4. The recharge altitude of geothermal water in Tangquan
样品编号 δ18O/‰ δ2H/‰ 补给高程/m H1 -8.83 -54.9 392 H2 -8.71 -56.2 354 H3 -8.00 -49.9 116 H4 -8.62 -54.3 321 H5 -8.74 -54.2 362 H6 -9.27 -55.8 539
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表 5 汤泉地区地下热水混合比例计算结果
Table 5. The mixing fraction of geothermal groundwater
样品编号 87Sr/86Sr Sr/(μg·L-1) 热水混合比例 冷水混合比例 H1 0.708876 4890 96% 4% H3 0.709299 1580 13% 87% H4 0.708916 4100 76% 24% H5 0.708901 4020 74% 26% H6 0.708997 4740 92% 8%
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表 6 地下热水中14C年龄校正结果
Table 6. The 14C age of the geothermal water samples based on correction model
样品编号 13C /‰ 14C /pMC 未校正前年龄/aBP Pearson (13C分馏)校正/a BP H1 -3.8 11.06 18203 6474 H2 -2.03 8 20880 3709 H3 -2.99 35.49 8564 M H4 -5.09 25.15 11411 2046 H5 -5.69 24.28 11702 3417 H6 -4.43 13.11 16797 6206 注：pMC为大气中现代碳的百分含量之比
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