Isotope Hydrology Studies in Geothermal Systems: Afyon-Oemer-Gecek Geothermal System

Nowadays, isotope techniques commonly used for defining the origin and flow direction of thermal waters. In many stages of geothermal development, stable isotopes such as 18O and 2H have distinct roles in defining the hydrological conditions and evaluating processes that affect the fluids. Radioactive isotopes such as 3H, on the other hand, are applied in specific problems as, dating and detection of recent coldwater inflow into geothermal reservoirs. Recent years, the isotopic investigation of geothermal systems indicates that geothermal fluids originate mainly from meteoric water. The 18O values of geothermal waters are most often higher than those of local meteoric waters, a trend in 18O - 2H diagram which has termed oxygen isotope shift. This has been interpreted as a result of isotopic exchange at high temperature between the water and the rock minerals which are richer in 18O. Within the scope of this study, the isotope data of Afyon Oemer-Gecek geothermal system which is one of the important geothermal areas in Turkey were interpreted. According to this study, thermal waters in Afyon Oemer-Gecek area are originated from meteoric waters but the recharge elevation is higher than cold waters and deep circulated. As a result, enrichment in 18O is indicated which is originated from water-rock interaction at high temperatures