ISOTOPIC AND GEOCHEMICAL TECHNIQUES APPLIED TO EFTENI AND DERDIN GEOTHERMAL SYSTEMS, NW TURKEY

摘要

The Efteni and Derdin low-temperature geothermal areas are located in north-western Turkey. Surface manifestations of relatively low-temperature springs (22–43°C) emerge on the Düzce fault, a normal component dominated fault segment in the North Anatolian Fault System (NAFS). Ionic characteristics of the geothermal springs generally are Na > Mg > Ca and HCO3 > Cl > SO4 . Isotopic and chemical evaluations show that there are two separate geothermal reservoirs in the area. Geothermometrical analyses applied to the Efteni and Derdin springs, representing these two separate reservoirs, reveal 113–135°C and 80–104°C respectively. Strong 18O shift has been observed in the Derdin spring which has ～2 TU of tritium content indicating recent recharges. In the scope of this study, the thermal reservoirs and the physical processes that affect both springs are distinguished, and the hydrothermal structures of the springs are determined by chemical and isotopic analyses. Geothermometric equations, which are used to estimate reservoir temperatures, have been correlated using isotopic techniques and, in particular, dilution processes, such as surface water mixing, have been distinguished in the Derdin Spring.