Hydrogeochemical Properties of Geothermal Fields at Northeastern Anatolia

In Anatolia which is one of exceptional continental regions hosting both Neogene volcanism and tectonism, the geothermal potential is quite high due to unique geological and tectonic structures. In recent years, the geothermal resources in western Anatolia, whose geothermal potential is well defined, are successfully used in a wide range of applications such as energy production, district heating, thermal tourism and greenhouse heating. However, the geothermal resources of northeastern Anatolia (NEA) have been used only in limited local-scale applications such as thermal tourism. Some of the geothermal fields in NEA region have been studied partly using physicochemical and isotopic techniques, leading to an understanding of water-rock interaction and origin of fluids. However, geothermal potential of these resources was not investigated from the perspective of hydrogeological conceptual model. In this study, hydrogeochemical properties and reservoir temperatures of 36 geothermal springs from 17 different geothermal fields in NEA region are investigated (in Ardahan, Artvin, Erzincan, Erzurum, Kars and Rize provinces). Waters which are of mostly NaHCO3 character have temperature, pH and specific electrical conductivity values varying between 18.57-63.20°C, 5.33-9.76 and 194-9580 µS/cm, respectively. The reservoir temperatures of Akdağ, Çat, Horasan and Ilıca (Erzurum) geothermal fields computed by Na/K and K/Mg geothermometers typically range from 70- 170°C and 48-88°C. The Na/K geothermometer results for the Köprüköy, Pasinler, Tekman and Uzunahmet (Erzurum) geothermal fields seem to be unrealistic (>160°C) while the temperatures calculated by K/Mg geothermometer are 45-87°C. A remarkable reservoir temperature of 107°C is obtained by K/Mg geothermometer for the Ġkizdere field (Rize). The Na/K geothermometers yield varying results between 71-123°C for Ayder while results from K/Mg geothermometer are similar to discharge temperatures. For low-temperature geothermal fields in the Artvin and Kars provinces, reservoir temperatures by K/Mg geothermometer are estimated between 71- 123°C