In spite of still disputed points, the Massif Central and Massif Armoricain are amongst the most studied places of the Middle Europa Paleozoic areas. The main tectonic, metamorphic, magmatic and sedimentary events are dispayed in chronological order in a synthetic table (Figure 14). The above presented scenario with two rifting-subduction-collision cycles accounts for the available lithologic, structural, metamorphic, magmatic and geochronologic data. Although often compared, the Paleozoic Variscan Belt significantly differs from the Himalayan one in the sense that collision is not restricted to two large continental masses such as India and Tibet but involves also several microcontinents. A modern analogue of such a complex pattern of island arcs, microcontinents and marginal seas between two converging continents could be found in the SW Pacific between SE Asia and Australia. One of the most striking features is that the two main ductile and synmetamorphic events, called here D1 and D2, are separated by about 25 Ma during which intra- or back arc rifting took place. The southward directed recumbent folds and thrusts well documented in the South Massif Central develop in Middle Carboniferous during the D3 event, do not appear as representative of the lithospheric convergence at the scale of the whole belt. Indeed, in the present orientation frame, the southward subduction of the Rheic Ocean below the northern margin of Gondwana is the major geodynamic feature of the Variscan orogeny. Lastly, conversely to the Alpine Collision Belt, the Variscan Belt is caracterized by a voluminous crustal melting giving rise to migmatites and plutons. Comparisons with the other segments of the same belt, such as Iberia or Bohemia, and even with coeval orogens such as Appalachians or Urals, would provide new insights and tests for this model.
Figure 14. Synoptic table
Synoptic table of the tectonic, metamorphic, magmatic and sedimentary events recorded in the Variscan French Massif Central and their interpretative geodynamic setting.