| 粤港澳大湾区地下热水地球化学特征及其热储含义 |
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| 引用本文：魏正安,黄少鹏,王成善,张敏.2023.粤港澳大湾区地下热水地球化学特征及其热储含义[J].地球学报,44(1):117-132. |
| DOI：10.3975/cagsb.2022.121701 |
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| 基金项目:国家自然科学基金项目(编号: U20A2096);深圳市高等院校稳定支持面上项目(编号: 20200827003238001);深圳市基础研究专项(自然科学基金)重点项目(编号: 基20220292) |
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| 中文摘要:粤港澳大湾区地热资源丰富, 但人们对区内地下热水地球化学特征的认识还存在一定争议。本文对27组地下热样品的水化学分析表明, 研究区内陆地热水的水化学相主要为重碳酸盐型, 沿海地热水则主要呈氯离子型。地热水的δ2H和δ18O值分别为–30‰ ~ –48‰和–5.2‰ ~ –7.5‰。内陆地热水的δ2H和δ18O值沿当地大气降水线(LMWL)分布, 表明内陆地热水来源于当地大气降水补给。沿海地热水的δ18O值偏离当地大气降水线并向海水数据点靠拢, 沿海地热水的δ18O值与Cl–含量呈强正相关, 表明沿海地热流体源于当地大气降水和海水混合补给。经典地球化学温标、多矿物平衡状态模拟、硬石膏-玉髓矿物对饱和指数模拟以及硅-焓混合模型揭示的粤港澳大湾区地热系统热储温度为104~156 ℃。内陆地热水中的地下冷水的混入比例为52%~84%, 沿海地热水中海水的混入比例高达37%。内陆和沿海地热水的最大循环深度分别为3300~4800 m和3200~4200 m, 没有显著差别。水化学组成与氢氧同位素研究均表明, 水岩反应和混合作用共同控制着研究区地下热水的地球化学特征。 |
| 中文关键词:氢氧同位素 补给来源 混合作用 热储温度 循环深度 |
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| Geochemistry and Its Geothermal Reservoir Implications of Geothermal Water in the Guangdong–Hong Kong–Macao Greater Bay Area, South China |
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| Abstract:The Guangdong–Hong Kong–Macao Greater Bay Area (GBA) in South China has abundant geothermal resources. However, the geochemistry of geothermal water in the area remains unclear. Hydrochemical analysis of 27 samples shows that the inland and coastal geothermal waters are mainly of bicarbonate and chloride types, respectively. The GBA geothermal water δ2H and δ18O ratios are in the range of ?30‰ to ?48‰ and ?5.2‰ to ?7.5‰, respectively. The δ18O and δ2H compositions of inland water samples fall along the Local Meteoric Water Line (LMWL), indicating its local precipitation origin. In contrast, coastal geothermal water is enriched in heavy isotopes, with δ18O values deviating from the LMWL towards those of seawater, with a strong positive correlation between δ18O values and chloride concentrations, suggesting that coastal geothermal water is recharged by a mixture of seawater and local precipitation. The combination of empirical chemical geothermometers, modeling of multi-mineral saturation states, anhydrite/chalcedony saturation indices, and silica-enthalpy mixing models suggests a reservoir temperature range of 104–156 °C for the GBA geothermal systems. The contribution of cold groundwater to the sampled inland geothermal water ranges from 52%–84% and the proportion of seawater mixing with coastal thermal water can reach up to 37%. The circulation depths of inland and coastal geothermal water are found to vary from 3300–4800 m and 3200–4200 m, respectively. Hydrochemical and isotopic compositions indicate that mixing with cold groundwater/seawater and water-rock interactions are the predominant factors regulating the geochemistry of geothermal water in the GBA, South China. |
| keywords:hydrogen and oxygen isotope source of recharge mixing process reservoir temperature circulation depth |
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