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Granitoid rocks of the southern Menderes Massif (southwestern Turkey): field evidence for Tertiary magmatism in an extensional shear zone

Recent field campaign in the southern Menderes Massif in southwestern Turkey revealed that the socalled 'core of the massif comprises two distinct types of granitoid rocks: an orthogneiss (traditionally known as augen gneisses) and leucocratic metagranite, where the latter is intrusive into the former and the structurally overlying 'cover' schists. These differ from one another in intensity of deformation, degree of metamorphism and kinematics. The orthogneiss display penetrative top-to-the-N-NNE fabrics formed under upper-amphibolite facies conditions during the Eocene main Menderes metamorphism (MMM), whereas foliation and stretching lineation exists in the leucocratic metagranites but are not strongly developed. The leucocratic metagranites show evidence of syn- to post-emplacement deformation in a series of weakly developed top-to-the-S-SSW fabrics formed under lower greenschist-facies (?) conditions. Leucocratic metagranite bodies occur all along the augen gneiss-schist contact in the southern Menderes Massif; they are emplaced as sheet-like bodies into country rocks (previously deformed and metamorphosed during a top-to-the-N-NNE Alpine orogeny) along a ductile extensional shear zone, located between orthogneisses and metasediments, which was possibly active during emplacement. The data presently available indicate that emplacement and associated ductile extensional deformation occurred during Late Oligocene-Early Miocene time. These results confirm previous contentions that there are Tertiary granites in this part of the Menderes Massif.