Structural and Metamorphic Evolution of the Northern Part of the Menderes Massif: New Data from the Derbent Area and Their Implication for the Tectonics of the Massif

The Menderes Massif represents the western part of the metamorphic axis of the Alpide orogen of Anatolia (Asia Minor). A restricted area in its poorly known northern part, around the village of Derbent, was studied to shed some light on its geological evolution and to compare it with that of the southern part of the Massif. In the Derbent area three lithologic groups are recognized on the basis of their lithology and structural position, namely the gneiss and the schist complexes and the marbles. Petrographic, mineralogic, and structural data indicate that the schist complex and the overlying marbles have undergone at least three phases of deformation and metamorphism. The first phase probably reflects the closure of the Karakaya marginal basin, located to the north of the present Menderes Massif, during the late Triassic. The traces of the first phase have been largely obliterated by the second phase, which led to amphibolite facies metamorphism. A pronounced, flat-lying foliation and a NNE-SSW trending mineral lineation was produced during this second phase which were the result of horizontal simple shear. During the second phase of regional metamorphism, temperatures reached 600-660°C and the pressure 5-6 kb, indicating a burial depth of 15 km. This phase is believed to have been the result of the collision between the Anatolide/Tauride Platform and the Pontides, which led to the internal imbrication of the former. A last retrograde metamorphism was the manifestation of the uplift, unroofing, and consequent cooling of the metamorphic complex, which created the present morphological "massif." During the Tortonian (late Miocene) to the present interval, E-W striking normal faulting and graben formation occured.