Investigation of petrology, geochronology and U – Th abundance of the central section (Aydın) of menderes massif

Menderes massif is the largest metamorphic massif of Turkey. At the base of the massif, there are Pan-African core rocks affected by metamorphism in granulite, eclogite and amphibolite facies, and overlying cover units affected by Alpine medium pressure Barrowian type metamorphism. This study was carried out to determine the origins, metamorphism conditions and age of granat mica schists covering large areas in the Central Menderes Massif. In the detrital zircon dating of schists derived from a quartzofeldspathic sources, the youngest zircon age was measured as 450 ± 61 Ma (102% concordant, Th/U = 0.02) Ma and the oldest zircon age was measured as 1529 ± 18 Ma (97% compatible, Th/U = 0.02) Ma. Mineral chemistry analyzes show that granats are almandine, biotites are Fe-biotite and white micas are muscovite-phengite type, and they are affected by metamorphism (greenschist - lower amphibolite facies) under 4.8 kbar pressure and approximately 596 °C temperature conditions. It is the first time, rutile U-Pb dating shows that granat micaschists underwent metamorphism 43.1 ± 6.1 Ma ago. PT conditions and metamorphism ages obtained from granat mica schists show that the cover units underwent metamorphism in the greenschist - lower amphibolite facies in the Eocene – Lutetian period. Lu-Hf isotope data show that the magmatism in which zircons are formed derives from the enriched mantle source area. Additionally, considering the zircon ages, it appears that this magmatism is a result of the magmatic activity associated with the Pan-African orogeny. The results of measurements made on different rock and mineral assemblages in terms of U-Th potential show that the source rocks have a potential in terms of both U and Th, but the necessary conditions for the formation of minerals containing uranium and thorium are not met.