Syn-convergence exhumation of continental crust: evidence from structural and metamorphic analysis of the Monte Cecu area, Alpine Corsica (Northern Corsica, France)

In the Corsica Island, a stack of metamorphic continental units derived from the European continental margin is thrust over a pre-Alpine basement during the convergence-related processes in the Late Eocene-Early Miocene time span. The Piedigriggio-Prato Unit is representative of these units. Its tectono-metamorphic history has been reconstructed by an integrated approach, ranging from map- to meso- and microscopic scale analyses. This unit is characterized by a polyphase deformation history that consists of three deformation phases developed under retrograde metamorphism ranging from blueschist to sub-greenschist facies metamorphic conditions. At the map-scale, the Piedigriggio-Prato Unit is characterized by km-size isoclinal folds deformed by open to closed recumbent folds producing Type 3 fold interference pattern. The features of the deformations and the P-T conditions suggest that the first two phases were acquired during the ductile extrusion of the Piedigriggio-Prato Unit. Before the Early Miocene, the gravitational collapse of over-thickened continental crust produced vertical shortening and the consequently recumbent F3 folds. The exhumation history of the Piedigriggio-Prato Unit can be viewed as representative for the exhumation of a continental crust fragment during the transition from the continental subduction to the continental collision. Copyright (c) 2016 John Wiley & Sons, Ltd.