The Kizildere thermal waters are located in the northern part of the Buyuk Menderes rift zone. The Paleozoic metamorphic rocks form the basement of the studied area and are discordantly overlain by Pliocene elastic sediments. The thermal waters are associated with NE-SW- and NW-SE-oriented faults, representing a compressional event that followed extensional formation of the rift zone. The hydrothermal alteration includes phyllic, argillic, silicic, hematitized, and carbonatized alteration zones.