Hydrochemical characteristics and formation mechanism of groundwater in Yushenfu Mining Area

The hydrochemical characteristics of groundwater in coal mining areas and its formation are of great significance to groundwater protection in mining areas and the identification of mine water inrush water sources. This paper takes the Quaternary aquifer, Cretaceous Luohe Formation, Jurassic Anding Formation and Zhiluo Formation aquifer groundwater as research objects in the Yushenfu Mining Area in northern Shaanxi. The chemical characteristics and formation of groundwater were analyzed by comprehensive use of statistical analysis, Piper's three-line diagram, isotope, Gibbs diagram and ion ratio relationship. The results show that the groundwater in this mining area is weakly alkaline fresh water. In the groundwater of quaternary, cretaceous Luohe Formation and Jurassic Zhiluo Formation （weathered bedrock）, the cation is mainly Ca²⁺, and the anion is mainly HCO₃ ⁻. In the groundwater of Jurassic Anding Formation, the cation is mainly K⁺+Na⁺, and the anion is HCO₃ ⁻. In the groundwater of Jurassic Zhiluo Formation （normal bedrock）, the cation is mainly K⁺+Na⁺, and the anion is mainly SO₄ ²⁻. TDS in the groundwater of each aquifer is significantly correlated with major ions. In the normal bedrock groundwater of the Luohe Formation and the Jurassic Zhiluo Formation, the spatial distribution of ions was quite different. Through isotope analysis and dissolution analysis, there is a hydraulic connection between the fourth series and the weathered bedrock aquifer of the Zhiluo Formation. The formation of main ions in groundwater in the study area is controlled by rock weathering, and the main ions are derived from the dissolution of carbonate, silicate, and sulfate minerals, and are affected by the alternating adsorption of K⁺, Na⁺, Ca²⁺, and Mg²⁺ cations. The results of this study can provide some reference for the protection and rational development and utilization of groundwater resources in the Yushenfu Mining Area.