Mineral chemistry and geothermobarometry of metasedimentary rocks of Central Menderes Massif, Western Türkiye: Metamorphic evolution and source of metapelitic rocks

Abstract

The Menderes Massif (MM) is the largest metamorphic massif of Türkiye. This study was carried out to determine the origins, metamorphic conditions and age of garnet-mica schists covering large areas in the Central Menderes Massif (CMM). Detrital zircon dating of a garnet-mica schist derived from a quartzofeldspathic source measured the youngest zircon age to be 450 ± 61 Ma (102 % concordant, Th/U = 0.02) Ma and the oldest zircon age to be 1529 ± 18 Ma (97 % concordant, Th/U = 0.02) Ma. The ƐHf_(t) values of the selected zircon grains vary between −27.42 and −3.43, and the ¹⁷⁶Lu/¹⁷⁷Hf isotope values vary between 0.2820 and 0.2827, and these values are consistent with the values obtained from the orthogneisses and paragneisses of the massif. The presence of five Ordovician zircon grains in garnet-mica schists and the intrusive contact with Triassic granites indicate that the source rock of the schists may have been deposited in the Late Ordovician - Triassic interval. Mineral chemical analyses show that garnets are almandine, biotites are Fe-biotite and white micas are muscovite-phengite in composition, and they are affected by metamorphism (greenschist - lower amphibolite facies) under ∼5 kbar pressure and ∼600 °C temperature conditions. For the first time, rutile UPb dating shows that garnet-mica schists underwent metamorphism 43.1 ± 6.1 Ma ago. PT conditions and metamorphic ages obtained from garnet-mica schists show that the overlying units underwent metamorphism in the greenschist-lower amphibolite facies in the Lutetian (Eocene) period.