The Menderes Massif geothermal province

Abstract

In the framework of the geothermal energy survey of western Anatolia Project, sponsored by the Mineral Research and Exploration Institute of Turkey and the United Nations, general geological investigations were made of the various geothermal provinces of western Anatolia. Most of the exploratory effort of the Project has been concentrated in prospective geothermal areas in and around the Menderes massif geothermal province. The Menderes massif geothermal province is one of the geothermal provinces distinguished in western Anatolia for exploratory purposes: Kayseri-Kozakli. Manyas-Apolvont-Bursa, Balikesir-Gediz, Izmir, Menderes Massif and Afyon. The Menderes massif geothermal province is essentially composed of the more or less metamorphic Menderes massif and its recent Mio-Pliocene filled graben complexes. This massif is bordered to the south by the Alpine folded Taurus chains, to the east by the Besparmak Dag and the Catmalidag, to the north by the Simav-Sindirgi graben complex and to the west by the Balikesir-Gediz and Izmir geothermal provinces. The Menderes massif geothermal province is characterized by particularly high heatflows in the Mio-Pliocene Bilvük and Kücük Menderes grabens and the Gediz and Salihli-Alasehir graben basins, and by a pronounced halo of partly very recent mercury mineralisations in the Menderes massif area on the north flank of the Büvük Menderes graben complex, on both sides of the Kücük Menderes graben basin and on the south flank of the Gediz and Salihli-Alasehir graben complexes. The high heat flow is indicated by the presence of numerous hot springs, geothermal fields and by numerous mercury deposits, some of which are being deposited today. There is some recent basic volcanism in the Kula and Esme areas on the northern border of this province. It therefore does appear that this heatflow is in any way directly associated with recent volcanic activity. It is presently thought to be due to the presence of one or more large magma chambers at depth, associated with a cooling batholite, probably of late Alpine age. This geothermal province is characterized by a series of E-W, NE-SW and NW-SE striking graben basins, which started their subsidence in early Miocene times, simultaneously with the arching of the Menderes massif as a whole, and continue such movements till the present day. This is clearly expressed by the high seismicity of these graben depressions. Two geothermal fields have hitherto been discovered: Kizildere and Tekke Hamam. both in the Saravköv-Denizli geothermal area. Only the Kizildere geothermal field appears to be commercial. No deep tests have been drilled hitherto in any of the other graben depressions. It is likely that similar fields may be located in other parts of this geothermal province also.