Geothermal potential of the eastern end of the Gediz basin, western Anatolia, Turkey revealed by three-dimensional inversion of magnetotelluric data

摘要

Three-dimensional models of the crustal electrical resistivity were derived from the inversion of magnetotelluric data in the eastern end of the Gediz basin, western Anatolia. In total, 179 MT sites measured in three different areas have been used in modeling. The study aims at providing information about the electrical resistivity distribution in the subsurface and its relations to structural setting and fluid pathways mainly controlling the development of geothermal reservoirs in the upper crust. The electrical resistivity models reveal a surficial low-medium resistivity layer associated with Neogene-Quaternary supradetachment sedimentary succession and a deeper high resistivity layer related to the Central Menderes Massif. The sedimentary cover over the metamorphic basement includes undulations, presenting an asymmetric extensional basin. The thickness of the sedimentary layer varies along strike from west to east and reaches approximately 3 km (max) in the graben. An anomalously conductive zone associated with a clay alteration zone was observed in this layer. The resistivity models also bring out two deep conductive zones along the southern margin of the basin: a conductive zone that could be interpreted as a geothermal reservoir at the easternmost end of the basin, however instead described as a part of a deep low resistivity zone with regional extent and another conductive zone interpreted as a region possessing an interconnected fracture network developed mainly by the extensional tectonic regime and that probably contains geothermal fluids. Moreover, normal faults exposing along the basin margins characterize the geometry of the basin, and particularly the main graben-bounding fault and Gediz detachment fault provide possible fluid pathways in the upper crust.