43rd IAH Congress, Montpellier, France, 25 - 29 September 2016, pp.1992
As a result of active volcanism and tectonism, the eastern Anatolian region in Turkey is represented by a high geothermal potential. In this study, we evaluate chemical and isotopic compositions of several geothermal springs in eastern Anatolia with emphasis on hydrochemical/isotopic characteristics and reservoir temperatures. Thermal waters were sampled in areas of Miocene volcanism (northeastern Anatolia) whilst some are collected in localities near historically-active volcanoes (e.g. Ağrı, Tendürek and Süphan volcanoes and Nemrut caldera) around Lake Van. Waters are mostly NaHCO3-type and their temperature, pH and electrical conductivity values are 16.26-81.30°C, 5.56-9.76 and 203-10434 µS/cm, respectively. Oxygen and hydrogen isotope compositions (–13.5 to –3.4 permil (VSMOW) and –92.1 to –64.5 permil (VSMOW), respectively) coincide with the Global Meteoric Water Line (GMWL); however, some samples plot close to the Mediterranean Meteoric Water Line (MMWL). Tritium contents are in the range of 0 to 3.2 TU. Carbon (d13C (VPDB): –17.5 to +6.9 permil) and sulfur (d34S (VCDT): –5.5 to +45.7 permil) isotope compositions imply marine carbonates and terrestrial evaporate units as the main source of dissolved carbon and sulfate in the waters. Temperatures estimated by SO4–H2O isotope geothermometry fall between 40 and 200°C and are generally not in agreement with reservoir temperatures computed from chemical geothermometers (~130 °C). 14C contents of thermal waters around Lake Van fall between 0.8 to 6.0% pmC and are equivalent to corrected ages of 8.2 to 28.8 ka.
Acknowledgements: This study is funded by the Scientific and Technological Research Council of Turkey (TÜBİTAK-ÇAYDAG project number: 114Y067).