PROVENANCE STUDIES IN NORTHERN GREECE

The Internal Hellenides are part of the Alpine-Himalayan mountain belt and attracted many geologists in recent times since the discovery of ultrahigh-pressure rocks in the Rhodope Massif about ten years ago. Much work has been done during the last decade to unravel the age and temperature/pressure history of the metamorphic rocks of the Rhodope Massif, which consists of two units: a lower tectonostratigraphic unit of Carboniferous–Permian age (Thracia Terrane) and an upper tectonostratigraphic unit of Jurassic–early Cretaceous age (Rhodope Terrane), separated by a suture zone. The adjacent unit to the west of the Rhodope Massif is the Serbo-Macedonian Massif, which comprises Palaeozoic metasedimentary and metaigneous rocks, intruded by Triassic rift-related granites. Further west and southwest follows the Vardar suture zone, including rocks of the controversial Circum-Rhodope Belt (CRB), which is the focus of this presentation. The tectonostratigraphic relationship between the CRB and the high-grade metamorphic rocks has been the subject of long discussions. The CRB comprises low-grade metamorphosed Triassic and Jurassic sedimentary rocks fringing the high-grade metamorphic rocks of the Serbo-Macedonian and Rhodope massives in northern Greece. Main outcrops are found in the easternmost part of the Vardar suture zone in the Chalkidiki peninsula (Melissochori Formation; formerly Svoula flysch) and in Thrace (Makri Unit and Melia Formation). Studying the age and provenance of these sediments is important for understanding the palaeotectonic history of the Vardar Zone (including the CRB) since the sediments there record a Neotethyan cycle of ocean basin opening and closure. Novel geochemical and isotopic data allow a critical re-evaluation of these sediments with regard to their age, provenance and geotectonic setting. The rocks record earliest Mesozoic intracontinental rifting followed by Early Jurassic rifting and opening of a Neotethyan ocean branch, Middle–Jurassic intraoceanic subduction and attendant volcanic-arc magmatism and ophiolite obduction leading to final ocean basin closure. Polyphase tectonics and metamorphism complicate palinspastic reconstructions.