Hydrogeochemical and isotopic investigation of Aydıncık-Kosrelik (Yozgat) geothermal and cold springs

The study area, Aydıncık-Kösrelik, is located in the northeast of Yozgat Province in the Central Anatolian Region of Turkey. The aim of this thesis is to reveal the hydrogeological origin by examining the existing physical, hydrogeochemical, isotopic (δ18O, δ2H, 3H) properties of geothermal and cold-water resources in the Aydıncık-Kösrelik (Yozgat) region, and to determine the possible reservoir temperatures of the reservoir system in the region by calculating with geothermometers. Water samples were taken from the study area for two periods, March (2022) and November (2022). The locations of the geothermal/cold water sources in the study area were determined by GPS, and the temperature, electrical conductivity and pH parameters were measured on-site. While chemical (major ion and trace element) and isotopic analysis (δ18O, δ 2H and 3H) were performed from the water resources in the study area, isotopic analysis (δ18O and δ2H) were performed from the snow samples as well. Ammonium (NH4), nitrite (NO2), nitrate (NO3), fluoride (F) and arsenic (As) pollutions were determined in some waters in the study area. Based on the hydrogeochemical and isotopic data, it is determined that the recharge of the KÖS-5 (geothermal) source can be from the south to the north of the study area at 1360-1416 m elevations, deeply circulated according to low 3H content, limestones of the reservoir rock is formed, and the possible temperature could be 31-42 ᵒC with respect to the silica geothermometer calculation. Furthermore, it is determined that the waters in the study area originate from meteoric water. In the study area, it is observed that spring waters except KÖS-2 might be suitable for irrigation. KEYWORDS: Geothermal, Aydıncık-Kösrelik (Yozgat), Hydrogeochemistry, Isotope, Pollution