The central part of the Zhangjiakou area is occupied by the Yanshan orogenic basin. A large number of piedmont faults developed over time, controlling the exposure of geothermal anomalies. The fluid chemistry characteristics and their influence on the heat generation mechanism of the medium- and low-temperature convective geothermal field in the area are not fully understood. In this study, the geothermal fluid was sampled and tested, and the hydrogeological background conditions were analyzed. The results show that the sulfate in geothermal fluid originates from the dissolution of gypsum or H₂S oxidation in deep magma. The geothermal fluid in the faulted basin flows upward after deep circulation and interacts with shallow groundwater. The main source of geothermal fluid is atmospheric precipitation. The temperature of the hot reservoir is between 82 °C and 121 °C, and the depth of geothermal water circulation is more than 3200 m. It can be seen that the geothermal resources in this area are formed by the long-term contact of residual magma, geothermal heating and mechanical heating of neotectonic movement after atmospheric precipitation recharge.

Xiongan New Area is located in the middle of North China Plain, with high background heat flow values and abundant geothermal resources. However, the degree of development of geothermal resources in Xiongan New Area is different, and the understanding of the hydrochemical formation and evolution is not comprehensive. Geothermal water and cold groundwater in Rongcheng uplift, Niutuozhen uplift, Baxian depression, Baoding depression and Gaoyang low uplift were sampled for hydrochemical analyses. There are two types of thermal reservoir in the study area: sandstone and karst thermal reservoir. Minghuazhen formation and Guantao formation had relatively shallow buried depth, and the hydrochemical types were mainly Cl·HCO3-Na and Cl-Na type. The main hydrochemical type of Wumishan formation was Cl·HCO3-Na. Due to the high degree of homogenization of karst reservoir, the spatial difference of hydrochemical characteristics was relatively small. From shallow to deep, the TDS value of geothermal water increased. Due to the influence of the water conduction in the fault zone, the mixing phenomenon of geothermal water in some deep Wumishan and Guantao formation occurred. The metamorphic coefficient and desulfurization coefficient of geothermal water in Wumishan formation were lower than that of Guantao formation, and the thermal storage was relatively closed and in relatively reduced state, while the sealing of geothermal water in Guantao formation and Minghuazhen formation was relatively poor. Our result is of great significance to understand the geothermal resources in Xiongan New Area and to promote the clean heating in winter in northern China.