Özet:

Afyon-Akşehir Grabeni (AAG), which represents the southeastern part of the Akşehir-Simav Fay System, is one of the active districts in Western Anadolu. KB-GD extension is controlled by living normal benefits such as Erkmen, Gecek, Gazlıgöl in the western part of the AAG. With water temperatures up to 130°C, the most important geothermal fields in this area, the Omer-Gecek and Gazlıgöl Geothermal fields are located in the intersection areas of Gecek and Erkmen Feyes and Gazlıgöl and Half-ca Feyes, respectively. The geological units in the area are composed of the Mesozoic rocks (reserve units) of the Afion Metamorphic Zone, which are disconnected from each other, the old Miyosen volcano-semianters and volcano units (cover units) and the modern swimming pool fillings of the Quaterner old alivial-fluvial and traverts. This study aims to define the environmental type of the geothermal fields mentioned above, using methods that include field studies such as geological maping and structural geology. The paleostres analysis and the current opening fractures measured on the foil plates that limit the pool indicate that the AAG is formed under the influence of multi-way extended tectonism, which varies from Pliyo-Kuvaterner, from D-B and KD-GB to KB-GD. The extension type is associated with the AAG’s KB-GD extended main graben fence with the connections of high-angle cross fence to this fence. Land-based studies show that the geothermal fields within the AAG indicate the geothermal environments of the type of extension area that develops in the crossing points of the living beams without active volcanism to the surface.

Anahtar Kelimeler:

Özet:

Afyon-Akşehir Graben (AAG) which consists of the southeastern part of Akşehir-Simav Fault System (ASFS) is one of the active depression areas in Western Anatolia. The western sector of the NW-SE-trending AAG is controlled by many active normal fault segments, namely Erkmen, Gecek, and Gazlıgöl Faults. Two main geothermal fields namely, Ömer-Gecek and Gazlıgöl contain reservoirs of fluid with temperatures up to 130° C, are located on the junction points of Gecek-Erkmen faults and Gazlıgöl-Yarımca faults, respectively. The area contains three unconformity bounded geological units; Mesozoic rocks of the Afyon Metamorphic Zone (reservoir unit), Miocene volcano-sedimentary succession (cover unit), including several sedimentary and volcanic units and Quaternary modern basin-fills of alluvial, fluvial and travertine deposits. This study involves use of geological mapping and structural geology methods to identify play type of geothermal fields mentioned above. Paleostress inversion analysis based on basin-bounding active faults and active extensional cracks along the travertine deposits shows that the AAG has been deformed under the control of multidirectional extension, with E-W and NE-SW to NW-SE orientations since Plio-Quaternary time. These types of extension are directly related with the linkage of cross faults that oriented at high-angle to the strike of NW-SE-trending major breakaway fault of AAG. Field-based studies also reveals that geothermal fields in AAG develops on the interactions of these active faults on the extensional domain type geothermal play without active volcanism coming to the surface.