In this study seasonal changes in the geochemical and stable isotope compositions of Hisaralan thermal waters in Simav Graben, western Turkey, were investigated with regards to a variety of mineral-water interactions and mixing processes. The Hisaralan and Emendere geothermal waters, with temperatures of up to 99 °C, were mostly of Na-HCO3 and Ca-HCO3 types. The δ18O and δ2 H values of the Hisaralan waters ranged from –‰ to –‰ and –‰ to –‰, with maximum seasonal differences of ‰ and ‰. The Emendere waters were represented by a more positive range of δ2 H values (–‰ to –‰), while their δ18O compositions (– to –‰) were very similar to those of the Hisaralan waters. | GÖKGÖZ et al. Turkish J Earth Sci Turkish Journal of Earth Sciences Turkish J Earth Sci 2021 30 182-203 http earth TÜBİTAK Research Article doi yer-2007-14 Multiple fluid-mineral equilibria approach to constrain the evolution of thermal waters in the Hisaralan geothermal field Simav Graben western Turkey Ali GÖKGÖZ1 Halim MUTLU2 Mehmet ÖZKUL1 Ali Kamil YÜKSEL3 1 Department of Geological Engineering Engineering Faculty Pamukkale University Denizli Turkey 2 Department of Geological Engineering Engineering Faculty Ankara University Ankara Turkey 3 Department of Geological Engineering Engineering Faculty Balıkesir University Balıkesir Turkey Received Accepted Published Online Final Version Abstract In this study seasonal changes in the geochemical and stable isotope compositions of Hisaralan thermal waters in Simav Graben western Turkey were investigated with regards to a variety of mineral-water interactions and mixing processes. The Hisaralan and Emendere geothermal waters with temperatures of up to 99 C were mostly of Na-HCO3 and Ca-HCO3 types. The δ18O and δ2H values of the Hisaralan waters ranged from to and to with maximum seasonal differences of and . The Emendere waters were represented by a more positive range of δ2H values to while their δ18O compositions to were very similar to those of the Hisaralan waters. The stable isotope compositions of the Hisaralan thermal waters were consistent with those of the global meteoric water line whereas the Emendere waters closely resembled those of the Marmara meteoric water line. The δ13C of the dissolved inorganic carbon varied from to for the thermal waters and from to for the cold waters. These values indicated a marine carbonate origin for the former and an organic source for the latter. Sulfur isotope systematics of dissolved sulfate in the Hisaralan geothermal waters indicated
