HP/LT metamorphism and the structure of the Alanya Massif, Southern Turkey: an allochthonous composite tectonic sheet

Abstract

Summary The southern part of the Alanya Massif is made up of three superposed, relatively flat-lying, crystalline nappes (Alanya Nappes), which tectonically overlie the largely sedimentary lithologies of the Antalya Unit (= Antalya Complex). The predominantly Mesozoic continental margin type lithologies of the Antalya Unit outcrop beneath the Alanya Nappes in a large tectonic window. The structurally lowest of the Alanya Nappes (Mahmutlar Nappe) consists of a heterogeneous series of shales, sandstones, dolomites, limestones and quartzites all metamorphosed under greenschist facies conditions. At least part of the sequence is Permian in age. The intermediate Nappe (Sugözü Nappe) is made up of garnet-micaschists which contain bands and lenses of eclogites and blueschist metabasites. Petrographic study has shown that rocks of the Sugözü Nappe have undergone initial HP/LT metamorphism followed by greenschist facies metamorphism. The greenschist overprint has destroyed most of the primary HP/LT mineral assemblages. The structurally highest of the Alanya Nappes (Yumrudaǧ Nappe) consists of a thick Permian carbonate sequence underlain by a relatively thin schist unit metamorphosed under lower greenschist facies conditions. The absence of HP/LT metamorphism in the structurally lowest and highest of the Alanya Nappes, and the greenschist facies metamorphism which has affected all three nappes indicate that the initial HP/LT metamorphism of the Sugözü Nappe was succeeded by the tectonic stacking of the Alanya Nappes, greenschist facies metamorphism and deformation. In post-Maastrichtian times the Alanya Nappes, which were by then welded into one unit, were thrust over the sedimentary rocks of the Antalya Unit. The final thrusting of the Alanya Nappes and the underlying Antalya Unit over the Tauride carbonate platform occurred before the Middle Eocene.