The ~(40)Ar/~(39)Ar age of extensional ductile deformation and granitoid intrusion in the northern Menderes core complex: implications for the initiation of extensional tectonics in western Turkey

摘要

The Simav detachment fault in the northern part of Menderes Core Complex in western Turkey, separates cover sequence rocks with brittle deformation, from high-grade metamorphic (core) rocks and young granitoid intrusions. The timing of shear zone formation and the intrusion of syn-tectonic granitoids is constrained by ~(40)Ar/~(39)Ar geochronology on muscovite from mylonitic gneiss, and biotite from the Egrigoz granitoid. ~(40)Ar/~(39)Ar data indicate that mylonitic deformation occurred at 22.86 ± 0.47 Ma, whilst the cooling age of the granitoid is 20.19 ± 0.28 Ma. The intrusion and cooling of the Egrigoez granitoid occurred between ～23-20 Ma. These data demonstrate that extensional deformation in the northern Menderes Core Complex began before Early Miocene times and represents an early stage in the Tertiary extensional tectonics of western Turkey.