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The Alpine evolution of the Ograzhden unit (Serbo-Macedonian Massif, SW Bulgaria)

Available ages and pressure-temperature estimates of the rocks from the Ograzhden unit of the Serbo-Macedonian Massif (SMM) in Bulgaria indicate a Variscan ultra-high-pressure metamorphic event at ~334 Ma (Trapp et al., 2021, Terra Nova 33, 174-183). The bulk of the Ograzhden unit are Variscan migmatites. Cretaceous amphibolite-facies metamorphism and deformation were reported from the Vertiskos unit in the Greek part of the SMM (Kilias et al., 1999, Int. J. Earth Sci. 88, 513-531) whereas the Ograzhden unit is considered to be largely unaffected by Alpine orogeny (Kounov & Gerdjikov, 2024, Geologica Balcanica 53, 29-85).

We present new structural data from the Ograzhden unit collected along a profile through the Triassic Igralishte pluton, documenting that along with at least two Variscan high-grade deformation events a substantial Alpine upper greenschist to lower amphibolite-facies overprint is present in the Ograzhden unit. Alpine ductile deformation is inhomogeneous and localised along several high-strain shear zones. This is in line with interpretations that the Ograzhden unit, and the SMM in general, forms part of the high-grade Rhodope Metamorphic Complex, although the Ograzhden unit is situated within the hanging wall of the extensional system that exhumed the Rhodopes in the Late Eocene to Neogene time.

Details

Author
Alex Jensen1, Jan Pleuger1
Institutionen
1Freie Universität Berlin, Germany
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/08vj-sb40
Geolocation
Balkans