Hydrogeological, Hydrogeochemical and Isotope Geochemical Features of Geothermal Waters in Simav and Environs, Western Anatolia, Turkey

Simav geothermal field is located in Simav graben within the Menderes Massif in Western Anatolia, Turkey. The geothermal waters in marbles, limestones and basalts can be classified as Na-HCO3-SO4 type exchange waters with the dominant cations in increasing order of Na+K>Ca>Mg while the anions are HCO3>SO4>Cl. The Cl-SO4-HCO3 ternary diagram shows that the waters are peripheral/immature and more likely related to groundwaters heated by steam from deeper reservoirs. Quartz, aragonite, calcite and chalcedony are oversaturated at discharge temperatures while at a recomputed temperature according to the reservoir composition, only quartz, dolomite and chalcedony are oversaturated. The silica thermometer shows reservoir temperatures between 83 and 1820C. The Na-K-Ca-Mg correction cation thermometers give reservoir temperatures close to the measured reservoir temperature on site in Eynal which is between 148 and 163 0C. The waters plot along the meteoric water line suggesting the source from local meteoric water and are rich in δ18O. This situation points to the existence of water-rock interaction in the system and/or boiling due to the high temperatures in the reservoir.