Hydrogeological, Hydrogeochemical and Isotope Geochemical Features of the Thermal Waters in Simav and Environs, Turkey

Abstract

Simav geothermal field, one of Turkey most important fields, is located in Kütahya Simav graben system of western Anatolia. This is on the eastern part of the graben and approximately 4 km north of Simav town and on the NE edge of the Simav plain, which is separated from the mountain by a high and steep escarpment. The plain covers an area of about 70 km2 and is at an altitude of about 780 m asl and lies on latitude 39 5 23 N and longitude 28 58 46 E. The thermal waters of Simav can be classified as Na-HCO3-SO4 type water with the dominant cations in increasing order of Na+K more than Ca more than Mg while the anions are HCO3 more than SO4 more than Cl. The Cl-SO4-HCO3 ternary diagram shows that the waters are peripheral/immature and more likely related to groundwater 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 geothermometer shows reservoir temperatures between 83 - 182C. The Na-K-Ca-Mg correction cation geothermometer gave reservoir temperatures close to the measured reservoir temperature on site in Eynal which is between 148 and 163 C. The waters plot along the meteoric trend line suggesting the source from local meteoric water and are rich in 18Oxygen. This situation points to the existence of fluid-interaction in the system and/or boiling due to the high temperature in the reservoir.