Hydrogeochemical research on fluids is an effective method to understand the formation mechanism, occurrence environment, and circulation process of groundwater. The groundwater sampling sites are located in the town of Dachaidan on the northeastern edge of the Tibetan Plateau, which was selected as the study object. Samples were collected from hot and cold springs and surface water in the area. This study is based on the analysis of water chemistry and isotopes, and aims (1) to discuss the chemical characteristics of groundwater in Da Qaidam, (2) to estimate the deep reservoir temperatures, recharge elevation and circulation depth of geothermal waters, and (3) to figure out the heat source beneath the geothermal area and its genetic mechanism. The result showed the following: The hydrochemical type of the hot spring is Cl·SO₄-Na and Cl-Na, and the hydrochemical type of cold spring is SO₄·HCO₃-Na·Ca and Cl·HCO₃·SO₄-Ca·Na. The main source of groundwater recharge is snow and ice melt water. The recharge elevation ranges from 4666.8 m to 5755.9 m. The geothermal reservoir temperature is about 119.15–126.6 °C. Ice and snow melt water infiltrate into the high mountainous areas on the north side of Da Qaidam and circulate underground through the developed deep and large fractures. Part of the groundwater migrates upwards under the water conduction of the Da Qaidam fault fracture zone to form cold springs, while another part is heated by deep circulation and exposed to the surface in the form of medium to low temperature tectonic hot springs. The research results can provide a scientific basis for geothermal resource exploitation and utilization in Qinghai Province.

The Waliguan–Duohemao tectonic belt on the northeastern Tibetan Plateau hosts Qinghai’s highest-temperature hot springs (Zhacanggou 98 °C, Qunaihai 97 °C) and deep hot dry rock resources in the Gonghe Basin. However, the mechanisms governing hydrothermal circulation in this region remain poorly understood, limiting the assessment of its sustainable geothermal development potential. Through integrated fluid geochemistry, borehole temperature logging, and crustal thermal structure analyses, this study reveals the dual “water–heat” control exerted by the fault zone. The fault acts as a dominant pathway for deep meteoric water circulation, controlling mixing between deep hydrothermal fluids and shallow cold water, as evidenced by continuous hydrochemical and isotopic trends. Heat flow analysis indicates surface heat flow values up to 134.66 mW/m² in the Gonghe Basin (with a 78.6% crustal contribution), decreasing to 57.4% in the Guinan area. A deep intra-crustal partial melting layer provides additional heat in the Gonghe Basin, whereas the Guide and Tongren areas rely primarily on radiogenic heat generation. The systematic increase in crustal heat flow from southwest to northeast confirms the fault zone as an efficient conduit for deep thermal transport, highlighting the region’s substantial deep geothermal energy potential. To overcome the “heat without water” exploration bottleneck and promote sustainable resource development, we propose differentiated exploration strategies tailored to the structural heterogeneity of the belt: (1) in the western Gonghe Basin, prioritize heat source characterization and enhanced geothermal system (EGS) feasibility assessment; (2) in the central Guide area, employ high-resolution geophysical methods to detect water-conducting fault zones; and (3) in the eastern Tongren area, evaluate water source conditions and fault connectivity with recharge areas. These strategies collectively minimize exploration risks and support the long-term, sustainable utilization of geothermal resources in this high-altitude region.