Using stable isotopes (δD, δ18O, δ34S and 87Sr/86Sr) to identify sources of water in abandoned mines in the Fengfeng coal mining district, northern China

Qu, Shen; Wang, Guangcai; Shi, Zheming; Xu, Qingyu; Guo, Yuying; Ma, Luan; Sheng, Yizhi

Using stable isotopes (δD, δ18O, δ34S and 87Sr/86Sr) to identify sources of water in abandoned mines in the Fengfeng coal mining district, northern China | Utilisation des isotopes stables (δD, δ18O, δ34S and 87Sr/86Sr) pour identifier l’origine de l’eau dans des mines abandonnées dans le district des mines de charbon de Fengfeng dans le Nord de la Chine Uso de isótopos estables (δD, δ18O, δ34S and 87Sr/86Sr) Para identificar las Fuentes de agua en minas abandonadas en el distrito minero de carbón de Fengfeng, norte de China 利用稳定同位素(δD,δ18O,δ34S和87Sr/86Sr)识别华北峰峰矿区废弃矿井充水水源 Uso de isótopos estáveis (δD, δ18O, δ34S e 87Sr/86Sr) Para identificar fontes de água em minas abandonadas no distrito de mineração de carvão de Fengfeng, norte da China

2018

With depleted coal resources or deteriorating mining geological conditions, some coal mines have been abandoned in the Fengfeng mining district, China. Water that accumulates in an abandoned underground mine (goaf water) may be a hazard to neighboring mines and impact the groundwater environment. Groundwater samples at three abandoned mines (Yi, Er and Quantou mines) in the Fengfeng mining district and the underlying Ordovician limestone aquifer were collected to characterize their chemical and isotopic compositions and identify the sources of the mine water. The water was HCO₃·SO₄-Ca·Mg type in Er mine and the auxiliary shaft of Yi mine, and HCO₃·SO₄-Na type in the main shaft of Quantou mine. The isotopic compositions (δD and δ¹⁸O) of water in the three abandoned mines were close to that of Ordovician limestone groundwater. Faults in the abandoned mines were developmental, possibly facilitating inflows of groundwater from the underlying Ordovician limestone aquifers into the coal mines. Although the Sr²⁺ concentrations differed considerably, the ratios of Sr²⁺/Ca²⁺ and ⁸⁷Sr/⁸⁶Sr and the ³⁴S content of SO₄²⁻ were similar for all three mine waters and Ordovician limestone groundwater, indicating that a close hydraulic connection may exist. Geochemical and isotopic indicators suggest that (1) the mine waters may originate mainly from the Ordovician limestone groundwater inflows, and (2) the upward hydraulic gradient in the limestone aquifer may prevent its contamination by the overlying abandoned mine water. The results of this study could be useful for water resources management in this area and other similar mining areas.

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