Study on the characteristics and genesis mechanism of geothermal resources in the Yangyuan Basin, Zhangjiakou, China

Objective The objective of this study is to elucidate the genesis mechanism of the geothermal system in the Yangyuan Basin, Zhangjiakou. This addresses a key scientific gap, as its genetic model has not been systematically explained, a deficiency that restricts the selection of high-quality exploration targets. Methods This study employed an integrated analysis of geological, geophysical, hydrogeochemical, and isotopic data. Furthermore, a comparative study with the neighboring Datong Basin was conducted to highlight the unique characteristics of the Yangyuan system.Results The results of this investigation show that geophysics reveals a deep thermal anomaly beneath the basin, associated with Datong volcanic activity. The reservoir system exhibits a dual-layer structure, dominated by Jixian carbonates, with localized Archean metamorphic fractures. This reservoir is overlain by thick Cenozoic sediments that act as a competent caprock. NW-trending deep faults and NE-trending basin-controlling faults provide pathways for fluid circulation and migration. The geothermal fluids originate from meteoric precipitation and undergo deep circulation and heating. Three genetic models were identified within the basin: fault-zone convective, deep-depression conductive, and fault-uplift composite. Conclusions The findings of this study indicate that the Yangyuan geothermal system concurrently possesses the high-quality reservoirs typical of stable cratonic basins and the active heat sources and pathways characteristic of rift zones. This reflects the composite nature of a tectonic–thermal transition zone. The polygenetic models proposed in this research provide a new theoretical framework for geothermal resource exploration within the rift basins of North China.