In this study, the hydro-geochemistry and stable isotope compositions (δ18O, δ2H, δ13C) of travertine-depositing springs were investigated in two regions of Garab and Pamukkale, located in NE-Iran and SW-Turkey, respectively. The physical, chemical, and isotopic dataset of water and travertine samples were obtained in-situ measurements, laboratory analysis and from the literature. According to the high EC values (~2400 and ~10500 S/cm); to hydro-geochemical properties; to the average δ13C-DIC values of water samples (10.4 and 7.2‰ VPDB); to released CO2 concentrations (316 and 673 mg/l) and its δ13C-CO2 values (1.5 and -1.8 ‰ VPDB which are enriched than the δ13C of CO2 originate from magmatic sources with values of −7 to −5‰ VPDB), it seems that the Garab and Pamukkale springs water were supplying from deep thermal groundwater with thermogenic origins and with contribution of carbonate dissolution through the rock-water interactions process. The more concentrations of Na+, K+ and Cl- in Garab water is related to subsequent admixture processes, which is originate from dissolving overloaded impure dissolve materials during upwelling water toward the ground level. The more enriched δ13C and δ18O values of Garab travertine samples (10.4 and -7.1 ‰ VPDB, respectively) than that of Pamukkale travertine (7.2 and -10.4 ‰ VPDB, respectively) is due to more CO2 degassing. The isotopic compositions of precipitation in both Garab (δ2H=7.2∗δ18O+11.2‰) and Pamukkale (δ2H=8∗δ18O+16‰) areas are characterized by greater d-excess compared to GMWL but smaller than of Mediterranean area. Although the isotopic compositions of both Garab and Pamukkale springs show the meteoric origin; however, the deviation from meteoric water lines is probably evident to oxygen isotope exchange with the deep host bedrock.

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