The increasing population and growing water demands have drawn global research attention to alternative water sources such as hard rocks aquifers. They play a crucial role in arid regions, where water resources are scarce. This study focuses on the volcanic belt of Torud–Chahshirin, situated in the south of Shahrood (Northeast Iran), to assess the geochemistry of water resources. This volcanic belt holds significant importance as it serves as the only water source for surrounding villages. Sampling was conducted during two wet (February 2017) and dry (July 2018) seasons from 34 springs and qanats and physico-chemical parameters (electrical conductivity, pH, temperature, major ions and heavy metals) and stable isotopes (18O and 2H) were measured. Spatial analysis revealed increasing electrical conductivity and temperature with reduction of pH along the flow path, primarily due to the dissolution of evaporate minerals (fracture filling halite and gypsum) and weathering of the silicates that enhanced the concentration of SiO2 with reduction in altitude along the flow pathways. Temporal changes in major ions indicated higher levels of ions in February as compared to July due to progress in dissolution and weathering processes. Halite and gypsum dissolution and weathering of silicate minerals were
determined as the main mechanisms controlling the geochemistry of the groundwater in this area. The concentration of heavy metals followed the order of Rh < Sb < Se < Mo < Sc < Ba < Li < Sr. They mainly sourced from geogenic origins, emerging in concentrations below WHO drinking standard except for Sr. Isotopic studies (18O and 2H) revealed that groundwater from the volcanic belt closely resembles local rainfall, suggesting that local water resources originate primarily from local atmospheric precipitations.