A comparison of hydro-geochemistry and stable isotope composition of travertine-depositing springs, Garab in NE Iran and Pamukkale in SW Turkey

In this study, the hydro-geochemistry and stable isotope compositions (delta O-18, delta H-2, and delta C-13) 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 (similar to 2400 and similar to 10,500 mu S/cm), the average delta(C-DIC)-C-13 values of water samples (10.4 and 7.2 parts per thousand VPDB), and its delta C-13-CO2 values (1.5 and - 1.8 parts per thousand VPDB), it seems that the Garab and Pamukkale spring 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-+,K- and Cl- in Garab water are related to subsequent admixture processes, which is originated from dissolving overloaded impure dissolve materials during upwelling water toward the ground level. The more enriched delta C-13 and delta O-18 values of Garab travertine samples (10.4 and - 7.1 parts per thousand VPDB, respectively) than that of Pamukkale travertine (7.2 and - 10.4 parts per thousand VPDB, respectively) is due to more CO2 degassing. The isotopic compositions of precipitation in both Garab (delta H-2 = 7.2*delta O-18 + 11.2 parts per thousand) and Pamukkale (delta H-2 = 8*delta O-18 + 16 parts per thousand) 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.