Article Dans Une Revue (Article De Synthèse) Geosciences Année : 2025

How Stiff Was Armorica During the Variscan Orogeny? A Reappraisal of the “Bretonian” Phase in Central Brittany

Résumé

In collision belts, the upper plate is generally less deformed than the lower one that underwent syn-metamorphic ductile shearing, and frequently late-collisional crustal melting. Concerning the Variscan orogeny, it is widely accepted that the Armorica microcontinent represented the upper plate of the collision system. In France, the Central-North-Armorican Domain belonged to this upper plate whose southern margin in the Pontivy-Coray area exposes metamorphic rocks. There, structural and metamorphic studies indicate that an early tectono-metamorphic event (M0-M1) with biotite-garnetstaurolite-kyanite assemblage, crystallized at 0.9 GPa and 500 • C, is characterized by a top-to-the NW shearing. This event was followed by an HT event (M2) at ca 800-900 • C, coeval with a domal structure. In micaschists, monazite yields an LA-ICP-MS age at 351 Ma ascribed to M2. M0-M1-M2 events developed before the Late Carboniferous pluton emplacement at ca 315 Ma (M3 event). The tectono-metamorphic succession documents that Armorica was not a rigid block but underwent a synmetamortphic ductile deformation during the Famennian-Tournaisian (360-355 Ma) collision redefined here as the late episode of the "Bretonian orogenic phase", whereas the pre-Famennian Bretonnian episode is ascribed to oceanic subduction. These new data allow us to reassess the geodynamic evolution of this part of the Variscan orogen.
Fichier principal
Vignette du fichier
geosciences-15-00060.pdf (15) Télécharger le fichier
Origine Fichiers éditeurs autorisés sur une archive ouverte
Licence

Dates et versions

insu-04940275 , version 1 (11-02-2025)

Licence

Identifiants

Citer

Michel Faure, Eric Marcoux, Marc Poujol, Clément Masson. How Stiff Was Armorica During the Variscan Orogeny? A Reappraisal of the “Bretonian” Phase in Central Brittany. Geosciences, 2025, 15, pp.60. ⟨10.3390/geosciences15020060⟩. ⟨insu-04940275⟩
0 Consultations
0 Téléchargements

Altmetric

Partager

More