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.

The Ayyubid Orogen: An Ophiolite Obduction-Driven Orogen in the Late Cretaceous of the Neo-Tethyan South Margin

“…The only exception to this statement is the Antalya Nappes. There the HP/LT metamorphism occurred in an entirely oceanic environment and the metamorphosed rocks were emplaced onto the continental margin later during the Paleocene as an already assembled package of nappes (Okay and Özgül 1984).…”

“…There is hardly a difference in the ages of the younger HP/LT metamorphic rocks in Oman and those in southeastern Turkey and the same is probably true for the Antalya Nappes within the Alanya Window (cf. Okay and Özgül 1984). This means that the nascent subduction zone was pulling the whole of Afro-Arabia down under some Tethyan plate and causing orogeny above it even before Africa turned northward with respect to Eurasia.…”

Preface

“…His formative years in the Survey between 1980 and 1983 were spent largely in the field in the Eastern Pontides, South-east Anatolia and in the Taurides doing basic geological mapping. During this time, Aral Okay, in collaboration with the great Tauride geologist Necdet Özgül, discovered the eclogites and blueschists in the Alanya Massif, and thereby solved the nappe structures of the Alanya Massif; the eclogites and blueschists occur in a relatively thin, flat-lying nappe sandwiched between two other metamorphic nappes showing only greenschist facies metamorphism (Okay, 1989a;Okay & Özgül, 1984). In south-east Anatolia Aral, with Cemal Göncüoğlu, mapped and studied the kyanite-eclogites in the Bitlis Massif (Okay, Arman, & Göncüoğlu, 1985).…”

U-series geochronology and geochemistry of vein and cave carbonate deposits in Turkey: the relationship between late Quaternary tectonic and climatic events

“…is located in the Cebel Reis Mountains of SW Turkey and occurs in faulted recrystallized Permian limestones of the Alanya Nappes ( Fig.1; Bozkaya & Yalçin 2004;Okay & Özgul 1984) capping Permian metamorphic basement, which is dominantly composed of mica-schist, quartzite, and dolomite ( Fig. 1; ).…”

“…4). It is argued that the partially dolomitic nature of the host carbonate rock is a result of interactions with Mg-rich fluids associated with metamorphic rocks in the basement Okay & Özgul 1984). Prolonged wall-rock interaction results in the dissolution of dolomite during drier conditions in response to the increased residence time of seepage waters, resulting in higher Mg/Ca ratios in drip waters and subsequently, in speleothems (e.g.…”