Late Palaeozoic palaeomagnetic and tectonic constraints for amalgamation of Pangea supercontinent in the European Variscan belt

摘要

This paper provides a review of the evolution of palaeomagnetic directions and sequence of tectonic events in the European Variscan belt during Late Palaeozoic times. These data are correlated with palaeomagnetic records from Gondwana and Baltica in order to provide a large-scale geodynamic framework during the Carboniferous to Permian. The Early Carboniferous palaeomagnetic records reported mainly from the Rhenohercynian and Saxothuringian magmatic arcs indicate a 70 degrees anticlockwise rotation, while Late Carboniferous to Permian magnetic directions from various rocks of western and central Europe are consistent with 120 degrees clockwise rotation of the eastern and central parts of the Variscan belt. Our review of the chronology of tectonic events is based on a robust database of geochronologically constrained deformation, metamorphic and magmatic events, which allow discretizing the 80 Ma long orogenic evolution into five principal events. In this scenario, the Variscan belt can be regarded as a linear sub-plate, isolated from Gondwana and Laurussia by the Rhenohercynian and Palaeotethysian oceans during Devonian times. This linear composite belt was segmented by transform faults and boundaries in the Late Devonian to Early Carboniferous times (360-335 Ma) during progressive E-W closure of Rhenohercynian ocean synchronously with collision between Saxothuringian and Moldanubian blocks. Subsequent relocation of subduction to the northern boundary Palaeotethysian ocean was responsible for N-S shortening almost orthogonal to the ancient sub-plate N-S elongation at around 335-325 Ma. This deformation resulted in dextral reactivation of transform boundaries associated with anticlockwise rotation of intermittent blocks. At the end of this rotation, the faults were parallelized to the Teysseire-Tornquist zone-the southern margin of Baltica, while the lozenge-shaped blocks of the former Variscan sub-plate were further shortened during continuous contraction. This evol