Geochemistry, active tectonic and relationship with young volcanics of Tekman (Erzurum) region geothermal waters

This study investigates the hydrogeochemical and isotopic characteristics of geothermal, cold spring (fountain), and surface (stream) waters in Yiğitler Village (Tekman district) and Çimenözü Village (Çat district) within the Erzurum province. The study area, encompassing geothermal fields in both regions, exhibits widespread exposures of volcanic, plutonic, and sedimentary rocks dating back to the Paleozoic to Pliocene periods. These hot water sources are influenced by tectonic and volcanic activity, surfacing through secondary shear faults that parallel the dominant NE-SW trending strike-slip faults. Geothermal waters in Yiğitler and Çimenözü display distinct characteristics: temperatures range from 43-49 °C and 45-54 °C, respectively; pH values fall within 7.03-8.33 and 8.2-8.69; and electrical conductivity (EC) values vary between 950-1550 and 925-1415 µS/cm. Chemically, both regions exhibit Ca-Mg-Na-HCO3-SO4 water types. Schoeller diagrams indicate a similar origin for the geothermal waters in both areas. Alpha activity ranges from 0.241-0.249 Bq/l and 0.193-0.406 Bq/l, while beta activity varies between 0.336-0.444 Bq/l and 0.426-0.723 Bq/l. Tritium (³H) isotope concentrations in the geothermal waters are low (0.32 Bq/l to 0.63-0.93 Bq/l), suggesting long-term deep circulation and rock-water interactions. Silica geothermometer calculations estimate reservoir temperatures between 55-141 °C and 62-168 °C in both regions. Major ion, trace element, and pollution analysis results for the geothermal waters comply with relevant regulations. However, compared to other geothermal waters in the Erzurum region, the Yiğitler and Çimenözü waters exhibit lower HCO3 concentrations and higher levels of Fe, Mn, and Al. Keywords: Çimenözü and Yiğitler (Erzurum), Hydrogeochemistry, Geothermal waters, Cold spring and surface waters, Tritium isotopes