| Abstract |
Simav geothermal field is located in the Simav graben system at K¸tahya province in western Anatolia. Geological units are mainly consisting of formations the Menderes Massif. The Kalkan formation and Simav metamorphics consist of migmatite, gneiss and schists of Precambrian - Paleozoic age, and accorded at the basement of the study area. The sequence continues upward with laterally and vertically interbedded, Paleozoic Balikbasi (marble), Saricasu (schist) and Arikaya (crystallized limestone) formations. The Triassic - Jurassic Budagan limestone rest on the above mentioned formation with angular conformity. The Paleocene Egrigˆz granite crosscut all the above mentioned units. Detritic and calcareous Kizilb¸k formation, Civanadag tuff and Akdag volcanic comprising of agglomerate, dacite, rhyodacite and rhyolite are Miocene in age, laterally and vertically interbedded to each other and, overlie the Egrigˆz granite unconformably. Coarse detritic Toklargˆl¸ formation, Eynal formation and Nasa basalt intercalating both formations occur at the top of the sequence. All of these formations are covered by actual alluvium. Joints and fractures developed in the Nasa basalt (1. reservoir rock), the Budagan limestone (2. reservoir), marble and limestone of the Arikaya and Balikbasi formations form secondary porosity and better permeability. The Eynal formation, Akdag volcanics, Civanadag tuffs, Kizilb¸k formation and Saricasu formation are impermeable and are cap rocks in character. According to the data obtained from wells drilled for the drinking and irrigation water purposes, ground water flow is toward the desiccated lake. Cold water analysis gave high CO3+HCO3, Ca, Mg ion values, and low NH4, NO3, Fe, NO2, Al and Mn ion values. Hot water analysis gave a cation trend of Na+K >Ca>Mg and an anion trend of HCO3+CO3>SO4>Cl .Cold water - hot water interactions and contaminated areas were determined by doing isotherm, resistivity and hydrochemical maps. Based on saturation indices, hot waters are saturated in respect to aragonite, calcite and dolomite and this indicates that rocks at the recharge area and reservoir are calcareous in composition. Isotopic analyses have shown that geothermal water is meteoric in origin and the circulation time of water is longer than 50 years. Reservoir rock temperatures have been calculated as being 148 - 180 ?C through geothermometric applications. |