Geochemical Properties and Determination of Turnover Time by Using 14C Isotope, in Kizildere and Tekkehamam Geothermal Field of Turkey

Abstract

There are many geothermal manifestations, in the temperature range from 35 to 242oC, on the eastern part of Buyuk Menderes Graben section. The investigated section of the Graben extends between Buharkent-Yenice and Pamukkale in the Aegean Region. Thermal springs, cold springs and deep wells of the fields were investigated by means of field measurements, chemical analyses and isotope analyses. By the means of this investigation the origin, the turnover time, the chemical characteristics and the recharge elevation of the area were determined. On these purposes, complete hydrochemical, 18O, 2H, 3H, 14C, 34S-SO4 and 18O-SO4 isotope analyses were realized. On the basis of topographical structure, geological formation and chemical properties, four primary and six intermediate types of ground water are recognized in the studied area. The deuterium-altitude relation of the shallow ground waters shows that the Kizildere and Tekkehamam field's thermal waters are approximately fed from 1300 - 1900 m.a.s.l. The 34S-SO4 and 18O-SO4 isotope analysis, reveal that the origin of the SO4 ion in Tekkehamam and its surrounding thermal springs, is from the dissolution of gypsum layers of the Pliocene aged Kolonkaya Formation. Due to the existence of high temperature in the reservoir, exchange between the 18O-SO4 and 18O-H2O isotopes takes place in the Kizildere's geothermal reservoir fluid. The rate of the exchange is calculated to range between 46 % and 84%. NETPATH was used in the interpretation. The 14C isotope calculation results refer to 22000 - 31000 years of turnover time for the geothermal fluid of the area.