| Keywords |
Hydrogeochemistry, Hydrogeology, thermal springs, environmental problems, geothermometers, mineral saturation, Bergama, İzmir, Turkey |
| Abstract |
Bergama is a touristic and historical city belonging to İzmir province, Western Anatolia, Turkey. Thermal waters in Bergama (ancient Pergamon) have been used for the purposes of bathing, therapy and spa facilities for ancient times tracing back Roman Period. In this study, geothermometry applications, mineral equilibriums, hydrogeological and hydrogeochemical properties of thermal waters in the Bergama geothermal fields are described by new data obtained from water points. These geothermal fields are geographically divided into four main groups; Güzellik Spa, Pasha Spa (ancient Allionai), Mahmudiye Spa and Dübek Place wells geothermal fields. Güzellik and Pasha Spas are located in Pergamon and Allionai ancient cities. Bergama and aforementioned geothermal fields are located in the Bakırçay graben, which is one of the western Anatolian grabens. Neogene volcanic rocks known as Yuntdağ volcanics I-II-III, of which components are andesitic components, are widely spreaded in the study area. The Yuntdağ volcanics-I form the aquifer of the geothermal systems in the area. Thermal waters also issue from these volcanic rocks through the intersection of faults. Alteration clays of the Yuntdağ volcanics-II may act as secondary cap rocks of the geothermal systems. Heat source is also high geothermal gradient due to the combination effect of the tectonic and volcanic activities. The thermal waters of Bergama vicinity have outlet temperatures of 25oC–58oC and EC values of 350-2320 μS/cm. Dominant cations are Na in all the thermal waters. Dominant anions for thermal springs are mostly HCO3 except for Dübek wells that are SO4. Chemical equilibrium modeling shows that the thermal waters are mostly oversaturated in aragonite, calcite, dolomite, and undersaturated in gypsum, anhydrite. Chemical geothermometers suggest average reservoir temperatures between 60oC–80oC. As well as these waters are used for balneological and touristic purposes, they should also be used for district and greenhouse heating. One important environmental problem in the study area is high arsenic contents of thermal waters produced from some wells near the Güzellik spa have been used for drinking purposes after cooling. So, thermal waters shouldn’t be used for the purposes of drinking and drinking cure. Another important environmental problem is that Pasha Spa waters, which are located in the famous archeological heritage Allionai, will remain under the reservoir waters of the planned Yortanlı Dam. |