Strain patterns within the late Variscan granitic dome of Velay, French Massif Central
1994; Elsevier BV; Volume: 16; Issue: 6 Linguagem: Inglês
10.1016/0191-8141(94)90149-x
ISSN1873-1201
AutoresJean-Louis Lagarde, Christophe Dallain, Patrick Ledru, Gabriel Courrioux,
Tópico(s)earthquake and tectonic studies
ResumoThe Velay granites are intruded as a late Variscan dome in the French Massif Central. Strain patterns within the Velay granites reflect the geometry and kinematics of late Carboniferous deformation, at the site of final emplacement. The internal deformation developed during granitic magmatism is not homogeneously distributed. From inner to outer zones increasing deformation is marked by changes from high-temperature foliations to S-C orthogneisses. Strain concentration at the margins reflects a strength contrast due to cooling and subsequent magma hardening. According to the internal strain field two zones can be distinguished in the Velay dome: (i) a central and southern zone where concentric patterns indicate a southward expansion of granites; and (ii) a northern zone where the lateral expansion is limited and combined with top-to-the-north extensional shearing along the Mont Pilat detachment zone and high-temperature wrenching. These asymmetric strain patterns relate to the expansion and deformation of granites emplaced below a detachment fault, during the uplift of a thickened area. Post-thickening combination of extensional and wrench tectonics is inferred.
Referência(s)