Structure and tectonic evolution of the Pirin‐Pangaion Structural Zone (Rhodope Massif, southern Bulgaria and northern Greece)

Abstract The Pirin‐Pangaion Structural Zone occupies the south‐western part of the Rhodope Massif. It consists of Proterozoic amphibolite facies metamorphic rocks of the Rhodopian Supergroup, and granitoids of Hercynian, Late Cretaceous and Palaeogene age. The pre‐Hercynian structure of the zone is dominated by an interference pattern of three superimposed fold generations of NE‐SW and NW‐SE trends. These structures are cut by Hercynian granitoids, and the entire complex is affected by late Hercynian or early Alpine conical folds. The zone was overthrusted by the Ogražden and Kroussia Units (Serbo‐Macedonian ‘Massif’) along the north‐east vergent Mid‐Cretaceous Strimon overthrust, and by the Central Rhodope Zone of the Rhodope Massif, along the south‐west vergent Meso‐Rhodopean Overthrust. With this thrusting event, the Pirin‐Pangaion Structural Zone was brought together with the Serbo‐Macedonian ‘Massif’ and the Central Rhodope Zone to form the Late Cretaceous Morava‐Rhodope Zone, which acted as a ‘plateau’ along the southern edge of the Eurasian plate. Late Cretaceous granitoid magma of crustal origin intruded this zone, whereas north of it the Srednogorie volcanic island arc was the site of igneous activity with magmas originating in the upper mantle. The West Thrace Zone developed as a Palaeocene to Oligocene depression superimposed over the older basement obliquely to the southern periphery of the Rhodope Massif. In the Late Eocene and Early Oligocene, this depression represented a volcanic island arc with mantle‐derived basic to intermediate magmas; contemporaneous granitoid magmas formed through crustal melting in the thickened crust of the Rhodope Massif (Pirin and Pangaion Units included). Early Miocene thrusting was most intense in the Pangaion Unit, and was followed by Late Miocene to Quaternary extension.