Occurrence Conditions and Hydrogeochemical Characteristics of High-Temperature Geothermal Resources in the Eastern Jiyang Depression

The eastern part of the Jiyang Depression possesses high-temperature geothermal resource potential due to the influence of the destruction of the North China craton, but there is a lack of systematic research on the occurrence conditions of high-temperature geothermal resources and the characteristics of geothermal fluids. Based on the results of geothermal well implementation and existing data, methods such as geothermal resource investigation, geothermal geological drilling, sample collection and hydrogeochemical analysis are employed to examine the occurrence conditions, conduct data analysis and complete water quality analysis and testing, hydrochemical types, ion sources, and evolution of high-temperature geothermal resources in the region. The genetic model of high-temperature geothermal systems in the eastern sedimentary basin is further explored. The results indicate that the uplifted areas within the depression are characterized by high heat flow, with Paleozoic carbonate formations serving as the key high-temperature geothermal reservoirs. The geothermal water predominantly exhibits a SO₄·Cl-Na hydrochemical type with high total dissolved solids (TDS), suggesting deep-circulation flow characteristics. The Na⁺ and Cl⁻ in geothermal waters primarily originate from the dissolution of minerals, precipitation-dissolution equilibrium of carbonate, sulfate and silicate minerals collectively influence the concentrations of Ca²⁺ and Mg²⁺. The main geothermal reservoir temperature ranges from 34.12℃ to 165.45℃, and the circulation depth of geothermal water is between 582.07 m and 4610.64 m. The water–rock interaction does not reach equilibrium, with the proportion of cold-water mixing ranging from 14.6% to 65.9% and the corresponding pre-mixing geothermal reservoir temperature ranging from 99.28℃ to 196.94℃. The study area represents a conductive-convective composite type geothermal system within a sedimentary basin, where mantle-derived material upwelling and magmatic activity following crustal thinning have contributed to the formation of high-temperature zones in the uplifted areas. The results of geothermal information provide a basis for the high-temperature geothermal resource exploration in this area.