Late orogenic magmatism and sedimentation within Late Carboniferous to Early Permian basins in the Balkan terrane (Bulgaria): geodynamic implications

摘要

The orogenic Balkanid belt, which developed between the Moesian Plate and the Moravian-Rhodopi-Thracian Massifs, was affected by the Late Carboniferous and Early Permian opening of W-E oriented graben structures. The progressive tectonic rejuvenation of the basins is demonstrated by the deposition of repeated regional sedimentary cycles, associated with volcanism that was mostly localised along the tectonic boundaries, in an intramontane setting.The Late Carboniferous volcanism is represented by rhyodacitic explosive products and hyaloclastites, and by andesitic flows. During the Early Permian, subvolcanic rhyodacitic and rhyolitic bodies and the explosive products prevailed in the western sectors, whereas rhyolitic ignimbrites occur to the east.The tectonically active basins are interpreted due to late orogenic collapse, and the alternation of extensional tectonics and minor compressional phases is consistent with the regional transtensional regime, active along the Variscan suture of Pangaea. The volcanic activity associated with the evolution of the basins matches the petrogenetic features and the evolution from early dacitic andesitic to late rhyolitic activity in the Southern European segment of the Variscan system.These Late Carboniferous-Early Permian sedimentary and tectono-magmatic events in Bulgaria are characterized, and compared with the homologous Permo-Carboniferous sequences along some western European segments of the Variscan belt.