Revealing the electrical properties of a gneiss dome using three-dimensional magnetotellurics: Burial and exhumation cycles associated with faulting in Central Anatolia, Turkey

Abstract

Abstract The Nigde Massif is a small-scale exhumed lithospheric entity in Central Anatolia formed as a result of metamorphism driven by crustal thickening and migmatization. Its thermal and structural history records two burial and unroofing episodes induced by oblique tectonics related to an adjacent wrench zone of the Ecemis Fault. To show the complex tectonic history of the events of this area, its electrical resistivity structure was determined using three-dimensional magnetotellurics. Forty-seven high-quality soundings within a frequency range of 320 Hz–5000 s were utilized for this purpose. The dimensionality of the data was investigated via phase tensor analyses and induction vectors. A hydrothermal system that might be related to Mt. Hasan was delineated as a widespread conductive zone. In addition, interpretation of the electrical resistivity models found a rheology-seismicity relationship in the study area. The Nigde Massif was depicted as a highly resistive dome-like anomaly bounded by low-angle detachment faults as indicated by the resistivity contrast between the massif and the adjacent features. The lower boundary of the massif is defined by a resistive to conductive transition situated at ∼25–30 km depth. Beneath this transition, a widespread low-resistivity zone was interpreted as a partially melting lower crust. This crustal feature is connected to a shallower anomaly beneath the Ecemis Fault Zone, which may infer the ascension of fluids that may be contributing to earthquake generation. Seismicity along the Ecemis Fault is overtly heterogeneous in that it tends to form a step approaching south along the fault where the lower crustal conductor is absent. Relevance between the seismicity and resistivity pattern denotes the presence of a fault configuration that is necessary for the yo-yo tectonics.