Tectono-metamorphic evolution of the northern Menderes massif: Evidence from the horst between Gördes and Demirci basins (West Anatolia, Turkey)

Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Geological Engineering, Turkey

Approval Date: 2004




The Menderes Massif forms a large metamorphic culmination in western Turkey ا an extensional province where continental lithosphere has been stretching following Palaeogene crustal thickening. Northern sector of the Massif on the horst between Gördes and Demirci Basins was chosen for structural analysis aimed to study the tectono-metamorphic evolution of the northern Menderes Massif. Within the study area, four groups of rocks are recognized: (1) the metamorphic rocks ا orthogneisses and metasediments; (2) pegmatoids; (3) Neogene sedimentary rocks; and (4) Quaternary alluvial sediments. The tectono-metamorphic history of the region involves a regional metamorphism (M1) at upper-amphibolite-facies conditions, coeval with a top-tothe-NNE contractional D1 deformation during the northward backthrusting of Lycian Nappes (Eocene main Menderes metamorphism). Partial anatexis during the latest stages of the M1 was speculated to be the main mechanism for the formation of the migmatites and the granitic magma. Pegmatoid domes and dikes/sills formed during late increments of this phase. A second metamorphism (M2) and coeval top-to-the-NNE deformation (D2) took place during the Early Miocene exhumation of the metamorphic rocks along a presently low-angle normal fault in an extensional shear zone at presumably greenschist facies conditions during declining P-T conditions. The latest deformation phase (D3) is high-angle normal faulting due to NاS extension affecting western Anatolia. The EاW grabens dissecting the Massif into northern, central and southern submassifs are the result of this phase, commenced during Pliocene-Pleistocene and gave the western Anatolia much of its present-day shape. The evidence presented supports the idea of episodic two-stage extension in western Turkey.