Hydrogeochemical and hydrogeological investigations of thermal waters in the Emet area (Kütahya, Turkey)

Abstract

Metamorphic rocks host the majority of the thermal waters of the Emet area. Only Dereli springs are hosted by non-metamorphic carbonates and ophiolitic rocks. The carbonated rocks of the lower parts of the Neogene sequence are also secondary reservoir rocks. The measured surface temperatures of thermal waters are between 33 and 54 °C. Most of the thermal waters are characterized as Ca–Mg–SO 4–HCO 3 type although there are a few Ca–Na–HCO 3, Na–Ca–SO 4 and Ca–Mg–HCO 3 waters. Calcium concentrations in the thermal waters are 89–354 mg/kg. High SO 4 contents of the thermal waters (up to 1309 mg/kg) are related to rocks and minerals in the Red Unit below the Emet borate deposits. Although the SO 4 concentrations are high and SO 4 is the major anion, gypsum and anhydrite are undersaturated for all of the thermal waters indicating that dissolution of SO 4 is still taking place in the reservoir. Thermal waters are oversaturated at outlet conditions with respect to calcite, chalcedony, dolomite and quartz. According to the activity diagrams thermal waters are likely to form illite as an alteration product in the reservoir and Ca and Mg contents are controlled by exchange with smectite. Reservoir temperatures obtained by silica geothermometers and assessments of the saturation states of minerals are more appropriate for Emet geothermal waters. Assessments of the various geothermometers suggest that reservoir temperature is around 75–87 °C.