POLYCYCLIC EVOLUTION OF THE HERCYNIAN BEL T

The Mid-European Palaeozoic Belt is often considered as the result of a continuous continental convergence from late Silurian to Carbonifero us. However, some stratigraphic, magmatic and structural data support a discontinuous evolution model. In late Silurian, the Eo-Variscan sta ge corresponds to a continental subduction responsible for a high pres sure metamorphism. During their exhumation, the high pressure rocks ar e partly melted. In North Massif central, the Eo-Variscan rocks are al ready outcropping in Middle Devonian. Since that time, evidence for a calc-alkaline magmatic are is found in the Massif central, Vosges and Massif armoricain. This are is due to the southward subduction of the Rheic Ocean. Tensional events such as the Brevenne rift, ligne des kli ppes and Bolazec areas in Massif central, Vosges and Massif armoricain respectively occur in the upper plate. These lines of evidence show t hat the Medio-Variscan period is heterogeneous since extensional tecto nics are followed by compressional ones belonging to the Hercynian Bel t proper. Therefore, the Variscan belt results of two orogenic cycles.