The geological and technical characterisation of Ömer–Gecek geothermal area and the environmental impact assessment of geothermal heating system in Afyon, Turkey

. Turkey, located in the Alpine–Himalayan Orogenic Belt, is of great interest because of its abundant geothermal resources. In particular, the Ömer–Gecek region of Afyon is one of the important geothermal fields in Turkey exhibiting high geothermal potential. The stratigraphic sequence, from bottom to top, comprises schist and marbles called 'Afyon metamorphics', Neogene sediments, and trachyte and trachyandesites, which are the products of Afyon trachytic volcanism, and Karakaya basalts. The basalt flows form the latest phase of the volcanic activities. The magma pockets forming the volcanic rocks are the source of heat for the geothermal system. Aquifer rocks forming Pasadagi marbles are aged Palaeozoic. Despite the high geothermal potential, Afyon is one of the provinces in Turkey suffering from air pollution. In order to utilize this potential and reduce air pollution problems, Afyon Geothermal Heating System (AFJET) was initiated in 1994 and put into operation in 1996 with an installed capacity of 10,000 residences out of which 4,453 have been successfully heated. If Tunçbilek–Kütahya coal, which contains 17.56% ash and 1.27% combustible sulphur was burnt instead of utilizing geothermal energy, approximately 768 tons of SOx,78,740 t of CO2 and 4,083 t of particulate matter would have been emitted to the atmosphere. The results obtained from Afyon experience reveal that not only the emission of tremendous amounts of pollutants is eliminated, but also a cheap energy alternative with an environmental friendly heating source is provided.