title: Assessment of the origin and geothermal potential of the thermal waters by hydro-isotope geochemistry: Eskisehir province, Turkey.
abstract: The thermal fluids vented over Eskisehir province have been investigated for their origin and to estimate the geothermal potential of the area. Thermal waters as well as bubbling and dissolved gases were collected and analysed for their chemical and isotopic features. Their isotopic composition varies in the range from -11.5 to -7.7 ‰ for δ18O, -84 and -57 ‰ for δ2H, and 0-7.2 TU for tritium. The gases (bubbling and dissolved) are mostly N2-dominated with a significant amount of CO2. The helium isotopic ratios are in the range of 0.2-0.66 R/Rac, indicate remarkable mantle-He contribution ranging between 2 and 10 % in the whole study area. Considering the estimated geothermal gradient about three times higher than the normal gradient, and the reservoir temperatures estimated to be between 50 and 100 °C using quartz and chalcedony geothermometers, a circulation model was built where possible mixing with shallow waters cool down the uprising geothermal fluids.
authors.affiliation: a Department of Geological Engineering , Hacettepe University , Ankara , Turkey.
authors.forename: Galip
authors.initials: G
authors.lastname: Yuce
authors.affiliation: b Istituto Nazionale di Geofisica e Vulcanologia , Sezione di Palermo , Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Italiano
authors.affiliation: c Department of Geological Engineering , Eskisehir Osmangazi University , Eskisehir , Turkey.
authors.forename: Didem
authors.initials: D
authors.lastname: Yasin
authors.affiliation: d General Directorate of Mineral Research and Exploration (MTA) , Ankara , Turkey.
authors.forename: Lutfi
authors.initials: L
authors.lastname: Taskiran
authors.affiliation: c Department of Geological Engineering , Eskisehir Osmangazi University , Eskisehir , Turkey.
authors.forename: Ahmet Hilmi
authors.initials: AH
authors.lastname: Gulbay
mesh_terms: D005618:Fresh Water / Q000032:analysis* / Q000737:chemistry; D006358:Hot Temperature; D007554:Isotopes / Q000032:analysis*; D008900:Mineral Waters / Q000032:analysis*; D011868:Radioisotopes / Q000032:analysis; D014421:Turkey
chemical_list: D007554:Isotopes; D008900:Mineral Waters; D011868:Radioisotopes
keywords: Carbon-13; Eskisehir; carbon dioxide; geothermal model; geothermometers; helium-3/helium-4; hydro-geochemistry; hydrogen-2; hydrogen-3; isotope hydrology; oxygen-18