Abstract: Menderes massif is commonly affected by extensional regime and a good example of forming a metamorphiccore complex. Simav detachment fault in the northern part of Menderes massif separated footwall and hanging wallrocks, which is thefeature of lithologic, metamorphism and deformation mismatch between them. The footwall consistsof medium-high grade metamorphites, pegmatoids andgranitoids. Schist-marble unit and ophiolitic melange comprisethe hanging wall. Neogene and Quaternary sedimentary and volcanic rocks lie both ımconformably and İn fault contact above the footwall and hanging wall rocks.Simav shear zone, characterized by deformed rocks below the Simav detachment fault, has two deformationalevents; these are ductile (mylonitic) and brütle (cataclastic) deformations. Ductile deformation event is the formation ofvariably developed mylonites in the footwall The degrees of mylonite development vary from protomylonite toblastomylonite. The majority of deformed rocks in the shear zone have mylonitic foliations and lineations. Myloniticfoliation is parallel and/or sub-parallel to the earlier foliation of metamorphic rocks. Mylonitic foliation is definedby preferred grain-shape orientation of biotite, muscovite and auartz ribbons. Lineation, other important element, isdefined by stretched auartz, and preferred orientations of feldspars, kyanite, hornblende and mica grains. The common kinematic indicators found in the zone is asymmetric porphyroclasts, mica fish, S-C and S-C fabric, recrystallizedoblique foliation, displacement grains and `V`-pull-apart fabrics. These asymmetric structures indicate a top-to-theN-NE shear sense. Recrystallization, neo-mineralization and other deformational features of grains in the shear zonesuggest medium-high-grade greenschist - amphibolite facies metamorphism conditions. Resent 40Ar39Ar isotopic dating implies that minimum age of shear zone is Oligocene - Early Miocene.Progressive stage of extension regime in the region constitutes brittle deformation that involves the development ofthe cataclastic zone below the Simav detachment fault and high-angle normal faults in later stage. Cataclastic zone,describing an area here affected by brütle deformation in the detachment fault of footwall, include breccia/cataclasitethat is product of mylonitic rocks of a variably fracturing, fragmentation, crushing, and alteration product. Exhumation of the northern part of Menderes massif was controlled by Simav shear zone. Structural, micro-tectonic featuresand izotopic data indicate that Simav shear zone is resultedfrom asymmetric exhumation of Menderes massif.