煤矿水害是陕北侏罗纪煤田的主要灾害，直罗组地下水是主要突水水源之一。为研究鄂尔多斯盆地北部直罗组地下水地球化学特征及其指示意义，借助Durov图、Piper三线图、Gibbs图、Stiff图以及主成分分析等手段，深入研究直罗组地下水地球化学特征，阐释其对直罗组与上覆含水层之间水力联系及地下水径流条件的指示意义。结果表明：自西部正常基岩区至东部风化基岩区，直罗组地下水pH以及TDS、K⁺+Na⁺、${rm{SO}}_4^{2 - } $、Cl⁻质量浓度均呈现出逐渐减小的趋势。直罗组地下水水化学类型存在一定差异，西部直罗组埋藏较深区域，地下水水化学类型以SO₄−Na型、SO₄·Cl−Na型和HCO₃·SO₄−Na型为主，向东至直罗组基岩风化区，地下水类型过渡为HCO₃−Ca型和HCO₃−Ca·Mg型等。直罗组地下水水化学形成受岩石风化作用、交替吸附作用、脱硫酸作用以及溶滤作用的控制。氢氧同位素和水化学特征对含水层之间水力联系具有明显的指示作用，氢氧同位素、典型钻孔地下水水化学离子浓度和区域地下水水化学特征分析表明，研究区西部直罗组正常基岩地下水与洛河组、萨拉乌苏组地下水基本不存在水力联系；东部直罗组风化基岩与萨拉乌苏组地下水水力联系紧密。卤族元素Cl⁻对直罗组地下水径流条件指示作用明显，研究区西部直罗组正常基岩地下水径流滞缓，地下水以静储量为主；而在基岩风化区，由于直罗组风化基岩孔隙、裂隙发育，储水性和渗透性明显增强，并与第四系地下水发生了强烈的混合作用，地下水径流强度大，地下水以动储量为主。

Coal mine water disaster is the main disaster of the Jurassic coalfield in the northern Shaanxi and the groundwater of the Zhiluo Formation is one of the main water inrush sources. Using the Durov diagram, Piper three-line diagram, Gibbs diagram, Stiff diagram and principal component analysis method, the geochemical characteristics of the Zhiluo Formation groundwater in the northern Ordos Basin and its indicative significance were investigated in this study. Also, it studied the geochemical characteristics of groundwater and explains its significance for the hydraulic connection between the Zhiluo Formation and overlying aquifer and the groundwater runoff conditions. The results show that the concentrations of the pH, TDS, K⁺ + Na⁺, ${rm{SO}}_4^{2 - } $ and Cl⁻ show a decreasing trend about the Zhiluo Formation groundwater from the western normal bedrock area to the eastern weathered bedrock area. And there are some differences about the Zhiluo Formation groundwater chemical types. For the deep buried area of the Zhiluo Formation in the west, the hydrochemical types of groundwater are mainly SO₄−Na type, SO₄·Cl−Na type and HCO₃·SO₄−Na type. For the bedrock weathering area of the Zhiluo Formation in the east, the groundwater type transitions to HCO₃−Ca type and HCO₃−Ca·Mg type. The hydrochemical formation of the Zhiluo Formation groundwater is controlled by rock weathering, alternating adsorption, desulfuration and leaching. Hydrogen isotope and oxygen isotope and hydro-chemical characteristics have obvious indicative effects on the hydraulic connection between aquifers. The analysis of hydrogen isotope and oxygen isotope, chemical ion concentration of typical borehole groundwater and regional groundwater hydro-chemical characteristics shows that there is no hydraulic connection between the normal bedrock groundwater of the Zhiluo Formation and the groundwater of the Luohe Formation and the Salawusu Formation in the western part of the study area. The weathered bedrock groundwater of the Zhiluo Formation in the eastern part is closely related to the Salawusu Formation groundwater. The halogen element (Cl⁻) has obvious indication effect on the runoff conditions of the Zhiluo Formation groundwater., The normal bedrock groundwater runoff of the Zhiluo Formation in the western is slow and the groundwater is mainly static reserves. For the bedrock weathering area, due to its development of pores and fissures, the water storage and permeability are significantly enhanced and there is a strong mixing effect with the Quaternary groundwater. So the groundwater runoff intensity is large and the groundwater is mainly dynamic reserves.