Hydrogeological Conceptual Model of Geothermal Waters in Baklaci (Alasehir, Manisa), Western Anatolia, Turkey

Abstract

Geothermal waters of Alaşehir are located in the southern part of the Gediz rift zone within the Menderes Massif and form biggest potential in the area with a capacity of up to 200 MWe. Geologically, Paleozoic metamorphic rocks with intercalations of micaschists, quartzites and marbles the gneisses from impermeable basement in the area underlying Precambriann to Cambrian gneisses. The both rocks are overlain by a Miocene intercalation of sedimentary rocks consisting of conglomerates, sandstones and clay stones and Plio-Quaternary intercalation of sedimentary rocks composed of conglomerates, sandstones and claystones discordantly. In the study area, Paleozoic quartzites and marbles form the main reservoir hydrogeologically. Geothermal waters with Na+K>Ca>Mg cations and HCO₃>Cl> anions are of Na-HCO₃ type and partial equilibrated waters. Geochemical thermometers show reservoir temperatures of up to 185 °C in accordance with measured temperatures in the production wells. Plot of δ¹⁸O versus δ²H in geothermal waters of Alaşehir deviate from the GMWL indication an intensive water-rock interaction. In the area of Alaşehir, geothermal waters are of meteoric origin. Finally, geothermal waters of Alaşehir are distinguished by a 2,0 percent CO₂ of productions in geothermal power plants especially which can represent an environmental danger in the area for future unless the steams with CO2 contents do not reinjcct into the geothermal reservoir.