HR: 1340h
AN: V13A-1142 INVITED    [Abstracts]
TI: Polymetamorphic complexes in the eastern parts of the Balkan Peninsula: 600 Ma of geodynamic evolution
AU: * Zagorchev, I
EM: i_zagorchev@geology.bas.bg
AF: Geological Institute, Bulgarian Academy of Sciences, Acad. G.Bonchev Street, Build. 24, Sofia, 1113, Bulgaria
AB: Polymetamorphic amphibolite-facies complexes are exposed in the eastern and central parts of the Balkan Peninsula in different Alpine tectonic zones and under different Cadomian to Alpine collisional and exhumation histories and regimes. All complexes consist mostly of biotite and two-mica gneisses and schists, and amphibolites. Strong Cadomian overprint led to intimate mixing (tectonometamorphic amalgamation) of crustal and mantle (and/or oceanic crust)-derived (serpentinized ultramafics, eclogites) products. The pre-Cadomian complex in Central Sredna-gora Mountains evolved through Cadomian collision with c. 617 Ma granites, Hercynian 340 to 250 Ma granitoids, Late Permian exhumation, and Triassic-Jurassic sedimentation followed by Mid-Cretaceous exhumation. P-T conditions never reached amphibolite facies in post-Cadomian times except for some shear zones. The pre-Cadomian amphibolite-facies complex in Sakar Mt. was intruded by c. 500 Ma old granites, deeply eroded in late Permian time, and covered with depositional contact by Triassic terrestrial and marine sediments. Both basement and Triassic cover suffered folding and amphibolite-facies metamorphism (c. 150 Ma BP) followed by exhumation. Included in the Srednogorie Late Cretaceous volcanic arc as crystalline cores, these complexes have been affected by latest Cretaceous exhumation. Amphibolite-facies polymetamorphic cores (Ograzhdenian complex) within the Serbo-Macedonian massif and other units in SW Bulgaria and the adjacent countries were subjected to intense Cadomian (560 – 520 Ma BP) synmetamorphic collision and granite activity. Some units suffered Cadomian collision under greenschist-facies with a Neoproterozoic to Cambrian diabase-phyllitoid complex or have been exhumed and directly covered by Cambrian (followed by Cambrian limestones) or Tremadocian marine sandstones. After Palaeozoic exhumation, their structure was sealed by Permian, Triassic and Jurassic terrestrial and marine sediments, and after intense Mid-Cretaceous folding and thrusting, exhumed again in Palaeogene times. In the Rhodope region, the Mesoproterozoic? to Neoproterozoic supracrustal Rhodopian complex is built up of kyanite-, garnet- and staurolite-bearing biotite and two-mica gneisses and schists, amphibolites, marbles, calcareous schists, quartzo-feldspathic gneisses (derived of possible arkosic or rhyolitic protoliths), and orthoamphibolite, metaperidotite and eclogite rootless bodies. Migmatites and anatexites crop out in the cores of Rhodopian domes. Mid-Cretaceous thrusting in greenschist-facies conditions is documented at the peripheries of the Rhodope massif, and probably contributed to considerable (up to 70 km; now about 50 km) crustal thickening in the interior. The cores underwent very late (Early to Late Palaeogene) exhumation. Eclogitic rootless bodies that witness HP to UHP metamorphic events crop out in all complexes mentioned. Eclogite formation is referred to different mechanisms (burial through subduction of oceanic crust; amalgamation of mantle and crustal slivers in depth; metamorphism of deep norite to troctolite intrusions; local increase of pressure and temperature along minor shear zones) and times (Cadomian, Hercynian, Cimmerian and/or Alpine).
DE: 1115 Radioisotope geochronology
DE: 8178 Tectonics and magmatism
DE: 9335 Europe
DE: 9620 Ordovician
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting