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The Paleozoic orogen that forms the backbone of Mid-Europa results from the collision between Gondwana, Laurussia and several microcontinents. The French Massif Central and Massif Armoricain belong to three tectonic and paleogeographic domains. Namely, the entire Massif Central and the south part of the Massif Armoricain belong to the North Gondwana margin, the Central Armorican Domain is a part of Armorica microcontinent and the Léon Domain is a piece of another microcontinent. The N. Gondwana margin and Léon Domain are made of a stack of syn-metamorphic nappes, conversely, the Central Armorican Domain consists of a Proterozoic basement built up by the Neoproterozoic Cadomian orogeny and a Paleozoic basement weakly deformed by upright folds related to wrench faults. The bulk architecture of the North Gondwana margin id the result of three main tectonic and metamorphic events that followed a Late Silurian high-pressure metamorphism whose associated structures are poorly documented. The Early Devonian D1 event (ca 385 Ma) is responsible for top-to-the-SW nappe stacking coeval with migmatization and exhumation of high-pressure rocks. The Late Devonian-Early Carboniferous D2 event (360-350 Ma) is associated to a medium pressure/temperature metamorphism during which top-to-the-NW shearing develops. The Visean D3 event (335-330 Ma) is characterized by contrasted tectonic regimes. A synmetamorphic top-to-the-south ductile shearing is widespread in south Massif Central whereas in north Massif Central, D3 is coeval with the onset of synorogenic extension. Orogen-parallel (E-W) extension develops coevally with Namurian-Westphalian plutonism, and orogen-transverse (N-S) extension took place in Late Carboniferous (ca 300 Ma). The Variscan Belt is also characterized by several magmatic events. The Early Cambrian and Early Ordovician pre-orogenic alkaline magmatisms correspond to the rifting events that separated Avalonia, Armorica and Léon microcontinents from Gondwana. The Early-Middle Devonian calc-alkaline magmatism is related to the Gondwana-directed subduction of the Rheic Ocean. Other magmatic events are due to the crustal melting that took place in Carboniferous times in response to D2 and D3 events. Late Visean and younger magmatic stages are coeval with extensional tectonics. These structural, metamorphic and magmatic events are replaced in a geodynamic evolution model at the scale of Western Europe.

In order to better understand the tectono-metamorphic evolution of the Thiviers-Payzac-type units in the Hercynian belt, three study areas have been chosen in Rouergue-Albigeois, Quercy and Central Vendée. These petro-structural studies allow us to settle the following tectonic evolution: During middle Devonian, a first event responsible for a south-westward thrusting of the Upper Gneiss Unit above the Lower Gneiss Unit is coeval with the emplacement of synkinematic calc-alkaline plutons. Around 360 Ma, a second top-to-the NW ductile and synmetamorphic event is responsible for the thrusting of the Thiviers-Payzac-type units on the previously structured units. A third phase occurring around 330Ma ago is characterised by a top-to-the south thrusting of the previously structured units upon the Albigeois-Montagne Noire series. The geodynamic significance of the second event is also discussed., Pour comprendre l'évolution tectono-métamorphique des unités de type Thiviers-Payzac dans la chaîne hercynienne, trois secteurs d'études ont été choisis: le Rouergue-Albigeois, le Quercy et la Vendée. Ces études pétrostructurales et géochronologiques ont permis de présenter l'évolution tectonique suivante: Au Dévonien moyen, un premier épisode provoque le charriage vers le SW de l'Unité Supérieure des Gneiss sur l'Unité Inférieure des Gneiss. Dans le Rouergue, les granites syntectoniques ont aussi enregistrés cette déformation. Vers 360 Ma, un deuxième épisode tangentiel provoque le charriage des unités de type Thiviers-Payzac vers le NW en contexte métamorphique barrovien. Lors d'une troisième phase vers 330 Ma, les unités précédemment structurées sont charriées vers le Sud sur l'ensemble Albigeois-Montagne Noire. La signification du deuxième épisode est également discutée en termes de géodynamique.

The Hercynian belt results of the collision between Gondwana, Armorica and Laurussia from South to North respectively. The French Massif Central which belongs to Gondwana experienced a complex kinematic history with several low-angle ductile and syn-metamorphic compressional and extensional events. The stack of nappes recognized in the whole Massif Central is also observed in Eastern Rouergue. In this area, the early nappe emplacement (named D1 event) is accommodated by a southward shearing which causes the superposition of the Upper Gneiss Unit above the Lower Gneiss Unit which itself overlies the Para-autochthonous Unit. A second event, D2, reworks the nappe pile with a top-to-the NW shearing. Porphyritic monzogranite plutons, called Pinet-type granites, record the D1 and D2 events. A petrostructural study of the Pinet-type plutons has been undertaken in order to understand the structural framework of the granite emplacement, and to better constrain the tectonic history of the Rouergue area. In order to characterize the relative timing and deformation mechanisms of the Pinet-type plutons, studies of textural relationships associated with quartz , and axes measurements have been realized. The D1 event is characterized by high temperature quartz axis sub-fabrics (600C-700C). The quartz axis sub-fabric are complex and do not provide clear kinematic data in agreement with other shear criteria. Two main mechanisms, active at high temperature near the subsolidus stage, explain the quartz c-axis development: oriented crystallisation process during the deformation and intracrystalline prism glide system. The D2 event is characterized by post-solidus quartz fabric with prism and basal glide systems active around 350C-450C. The shear sense given by the asymmetric fabric is in good agreement with the other shear criteria and demonstrates a top-to-the NW shearing.