From Early to Middle Miocene, the continental rift zones of the Buyuk Menderes, the Kucukk Menderes and the Gediz were formed by extensional tectonic features, which generally strike E-W and are represented by a great number of geothermal waters, epithermal Hg, Sb and Au mineralizations, and volcanic rocks of Middle Miocene to recent age. The geothermal waters and epithermal mineralizations are related to faults, which strike preferentially NW-SE and NE-SW and are located transversely to the general strike of the rift zones. These faults are probably generated by compressional tectonic stress, which leads to the deformation of uplift between two extensional rift zones. One of these continental rift zones is the rift zone of the Buyuk Menderes which is ascribed to a great number of geothermal waters such as those issuing in very important locations of Kizildere, Tekkehamam, Salavatli, Germencik and others with a geothermal capacity of 860 MWe in the next future. The geothermal waters of Tekkehamam and surroundings are identified to belong to the Na+K>Ca>Na and HCO3>SO4>CI facies. According to the Cl-SO4-HCO3 diagram the geothermal waters might be heated by a magmatic source due to the high content of sulfate and boron in geothermal waters. Geochemical thermometers were applied to the collected samples in the region. According to the Na-K-Mg diagram (1), part of the geothermal waters can be considered as equilibrated geothermal waters. According to the results of geochemical thermometers, the reservoir temperatures of geothermal waters range from 160 to 250 degrees C. The delta H-2 values of geothermal waters are between -61.9 to -51.8, while delta O-18 values range from -9.23 to -5.84. The tritium contents of geothermal waters are between 0.7 to 3.3 TU. These results show that there is no mixing with cold groundwaters. (C) 2017 The Authors. Published by Elsevier B.V.