A conceptual model for groundwater flow and geochemical evolution of thermal fluids at the Kızılcahamam geothermal area, Galatian volcanic Province

The isotopic values of thermal water (δ18O, δ2H, δ3H) indicates their deep-circulating meteoric origin and allow estimation of infilitration altitude ranging between 1350 and 1750 m.a.s.l.This datum, supported by structural data, suggests the Işıkdağ and Aluçdağ Mountains as the recharge area of the system. As frequently observed in many geothermal systems positive I8O shifts of Kızılcahamam thermal waters relative to the local meteoric line were considered to be primarily due to interaction with host rocks at elevated temperature (T > 150 °C) and from CO2 exsolution of thermal and mineral springs. In this system, geothermal waters are heating by an intrusive-cupola and geothermal gradient, followed by the waters rising to the surface along faults and fractures that act as hydrothermal conduits. A conceptual hydrogeochemical model was developed for a hydrogeological flow system in the Kızılcahamam Region.