Hydrogeochemistry and genetic mechanisms of the geothermal system in the Xi'an depression of the southern Weihe Basin, China

•Three water types were identified: HCO3·SO4-Na, SO4·HCO3-Na, and SO4·HCO3·Cl-Na.•The thermal storage temperature ranges from 90 °C to 190 °C in the Xi'an depression.•The circulation depth of thermal storageis ranges from 1429.42 to 3103.22 m in the Xi'an depression.•The genetic mechanism of the geothermal system was revealed in the Xi'an depression. Investigating hydrogeochemistry in geothermal fluids is a valuable approach to comprehending the intricate process of deep geothermal water circulation and uncovering the underlying mechanism behind the formation of geothermal systems. The article presents a thorough investigation of the hydrogeochemical and stable isotope characteristics of geothermal fields situated on both the southern and northern sides of the Xi'an depression. This study elucidates the process and progression of deep geothermal water, thereby offering theoretical backing for the exploitation of geothermal resources in the Weihe Basin. The data indicates the following points. The predominant chemical composition of geothermal water consists of SO4·HCO3–Na and SO4·HCO3·Cl–Na types. The ionic components are mainly impacted by the dissolution of Silicate and evaporite minerals, as well as the alternating adsorption of cations. The geothermal water is replenished by rainfall from the Qinling Mountains, with the recharge elevation varying from 677.94 m to 1,467.65 m. Various techniques are employed to determine the temperature and depth of the reservoir, which helps to understand the behavior of the deep thermal water. Thus, the study determines that the geothermal water in the Xi'an depression originates from laminar-controlled geothermal reservoirs, lateral flow recharge, and an unusual deep thermal structure.