Alpine metamorphic and tectonic evolution of contact between Variscan and alpine Corsica in the Corte-Inzecca area (Corsica, France)

Category Tectonic & Seismotectonic
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Garfagnoli, Francesca; Menna, Francesco; Pandeli, Enrico; Nirta, Giuseppe; Principi, Gianfranco
Holding Date 20 September 2008

The island of Corsica is formed by two different geological domains: a) Variscan Corsica, which represents the western 2/3 of the island and is formed by Carboniferous to Permian granitoids and associated volcanics, together with Lower Paleozoic metamorphic country rocks and remnants of a Late-Paleozoic?-Late Eocene sedimentary cover; b) Alpine Corsica, which constitutes the north-eastern 1/3 of the island and is made by a complex tectonic pile including both metamorphic oceanic- (Schistes Lustrés) and continental- (e.g. Serra di Pigno/Farinole, Centuri) derived thrust sheets. The Schistes Lustrés are underlain by some tectonic units, such as the Tenda Massif, the Corte slices, the Santa Lucia Nappe and the Caporalino-Pedani Nappe, that are considered to be Alpine tectonic slices of the European continental margin (Parautochtonous Units). Many recent works carried out on the Alpine Corsica pointed out that Tertiary deformations associated to high pressure/low temperature metamorphism occurred not only in the oceanic metamorphic units (Schistes Lustrés) as it has long been known, but also in the tectonic slices derived from the continental margin of the European plate and located along the northern part of the contact between Alpine and Variscan Corsica.
In the area comprised between Corte and the Inzecca Massif, a complex assemblage of vertically juxtaposed tectonic units, affected by Alpine deformations and metamorphism, crops out. Among them, the Parautocthonous Units represent fragments of the Corse basement (Paleozoic granitoids and associated volcanic and metamorphic pre-Carboniferous rocks) and of its Mesozoic to Tertiary sedimentary cover, that are tectonically sliced between the allocthonous Ligurian-Piedmontese Units (Schistes Lustrés) and the autochthonous basement (Variscan Corsica).
The new 1:10.000 geological mapping, together with structural analyses at the meso- and microscale, petrographical and mineral chemistry analyses, performed in the southernmost sector of the boundary between Alpine Corsica and Variscan Corsica, provides new data that point out an Alpine polyphasic deformation and metamorphic evolution (from blueschist facies to greenschist facies) in the Parautocthonous continental-derived units, stacked between the Schistes Lustrés of the Alpine Corsica and the autochthonous basement. These data support the hypothesis of the involvement of a wide part of the European continental margin in the Late Eocene-Oligocene subduction-related tectonics during the Alpine orogeny.