Origins and mixing contributions of deep warm groundwater in a carbonate-hosted ore deposit, Sichuan-Yunnan-Guizhou Pb-Zn triangle, southwestern China
Origins and mixing contributions of deep warm groundwater in a carbonate-hosted ore deposit, Sichuan-Yunnan-Guizhou Pb-Zn triangle, southwestern China
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DOI：
10.1016/j.jhydrol.2020.125400
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发表时间：
2020-11
影响因子：
6.4
通讯作者：
He Huang;Zhi-hua Chen;Tao Wang;Gaoming Zhou;Jonathan B. Martin;Liang Zhang;Xianmeng Meng
中科院分区：
文献类型：
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作者：
He Huang;Zhi-hua Chen;Tao Wang;Gaoming Zhou;Jonathan B. Martin;Liang Zhang;Xianmeng Meng
川滇黔碳酸盐岩型铅锌成矿三角带是我国最大的铅锌成矿带，属密西西比河谷型铅锌成矿带。然而，很少有人知道的水-岩相互作用涉及矿床和现代水文系统的影响。通过对深部地下水化学和同位素组成的测定，分析了地下水的来源、潜在循环深度、反应温度以及与浅层地下水的混合过程，从而评价了区域水文地质与矿床之间的可能联系。在茅坪子矿床内，深层地下水温度较高（21.2-32.0 °C），pH值较低，HCO 3 −和SO 42 −浓度较高，平均87 Sr/86 Sr比值较高（0.7148）和Sr浓度（4.1 mg/L），δ 13 CDIC值较正（−4.5 ~ −4.2‰），平均同位素值（δD = −98，δ 18 O = −13.7‰）较浅，表明其来源与现代地表补给不同。深层温水的轻同位素组成表明，在过去，可能在末次冰盛期在较冷的温度下进行了补给。δ 13 CDIC值反映了深部地下水与周围岩石之间的同位素平衡，沿着可能存在深部CO2来源。硫化物的氧化过程，包括与成矿过程相关的H2S和黄铁矿，可以产生硫酸，增强碳酸盐溶解，并产生升高的HCO 3 −和SO 42 −浓度。根据石英地质温度计，深层地下水的反应温度似乎在50-65 °C左右，鉴于区域地热梯度为24.1 °C/km，这表明反应发生在地表以下约1 900米的深度。放射成因Sr同位素比值的Sr浓度升高反映了深循环过程中与基底岩石和碳酸盐岩的反应。锶浓度和同位素混合模型表明不同的补给来源，并建议深温暖的地下水捕获矿井排水的贡献。这些结果反映了深层地下水循环和反应的重要性，在一个大型存款，可以提高这些重要的矿体对区域水成分的SYG三角和其他MVT矿床的潜在影响的理解。
Sichuan-Yunnan-Guizhou (SYG) carbonate-hosted Pb-Zn triangle is a world-class metallogenic belt and classified as Mississippi Valley-Type (MVT), which provides the greatest ore production in China. However, little is known about the effects of water-rock interactions involving the ore deposits and the modern hydrologic system. Measured chemical and isotopic compositions of the deep groundwater are used to evaluate water origins, potential circulation depth, reaction temperatures, and mixing process with shallow groundwater to assess possible linkages between regional hydrogeology and ore deposits. Within the Maoping sub-deposit, deep groundwater is warmer (21.2–32.0 °C), has lower pH, higher HCO3−and SO42−concentrations, higher average87Sr/86Sr ratio (0.7148) and Sr concentration (4.1 mg/L), more positiveδ13CDICvalues (−4.5 to −4.2‰), and lighter average isotopic value (δD = −98 andδ18O = −13.7‰) relative to shallow groundwater, suggesting an origin distinct from modern surface recharge. The light isotopic composition of the deep warm water indicates recharge at a cooler temperature in the past, perhaps during the Last Glacial Maximum. Theδ13CDICvalues reflect isotopic equilibrium between deep groundwater and surrounding rocks along with a possible deep source of CO2. The oxidation process of sulfides, including H2S and pyrite linked to the ore-forming processes, could produce sulfuric acid that enhances carbonates dissolution and generates elevated HCO3−and SO42−concentrations. Reaction temperatures for the deep groundwater appear to have been around 50–65 °C based on quartz geothermometers and given a regional geothermal gradient of 24.1 °C/km suggest reactions occurred at depths ~1900 m below the land surface. Elevated Sr concentrations with radiogenic Sr isotope ratios reflect reaction with basement rocks and carbonates during the deep circulation. Sr concentration and isotope mixing models demonstrate different recharge sources and suggest the contribution of deep warm groundwater captured in mine drainage. These results reflect the importance of deep groundwater circulation and reactions in a large ore deposit that may improve understanding of potential effects of these important ore bodies on regional water compositions in the SYG triangle and other MVT ore deposits.