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The subduction of continental crust is now a matter of fact but which are the mechanisms and the factors controlling the exhumation of continental units and their coupling with oceanic units are still a matter of debate. We herein present the tectono-metamorphic study of selected continental units belonging to the Alpine Corsica (Corte area, Central Corsica, France). The tectonic pile in the study area features thin slices of oceanic units (i.e. Schistes Lustres Complex) tectonically stacked between the continental units (i.e. the Lower Units), which record a pressure–temperature-deformation (P-T-d) evolution related to their burial, down to P-T-peak conditions in the blueschist facies and subsequent exhumation during the Late Cretaceous – Early Oligocene time span. The metamorphic conditions were calculated crossing the results of three different thermobarometers based on the HP-LT metapelites. The continental units only recorded the P-peak conditions of 1.2 GPa-250 °C, up to the T-peak conditions of 0.8 GPa-400 °C, and the retrograde path up to LP-LT conditions. The metamorphic record of the oceanic units includes part of the prograde path occurring before the peak conditions reached at 1.0 GPa-250 °C followed by the last metamorphic event related to LP-LT conditions. The results indicate that each unit experienced a multistage independent pressure–temperature-deformation (P-T-d) evolution and suggest that the oceanic and continental units were coupled during the rising of the last ones at about 10 km of depth, where the oceanic units were stored at the base of the wedge. Subsequently they were deformed together by the last ductile deformation event during exhumation. We propose a mechanism of tectonic erosion at the base of the wedge, by which slices of Schistes Lustres Complex were removed at the roof of the plate interface during the exhumation of the Lower Units.

International audience; This paper provides a field description and an analytical characterization of the fibrous minerals associated with ultrabasic and basic rocks from the Corsican Ophiolitic Complex, on the island of Corsica, in order to examine their asbestos potential. Thirty-five fibrous samples taken from serpentinites, magnesium-rich meta-gabbros and meta-basalts were studied, using combined EPMA, Ramanand FESEM methods. The results highlight that naturally occurring asbestos (NOA) are abundant in serpentinites and regularly occur in magnesium-rich meta-gabbros and meta-basalts in northern Corsica. The spatial distribution, abundance and mineralogical types of these NOA strongly depend on the petrographic nature of the hosting rocks and their structural pattern. NOA in serpentinites correspond to chrysotile vein networks in the internal parts of the thickest rocky masses and to tremolite veins and shear planes carrying tremolite fibers, both in the external parts of these masses and in highly sheared serpentinites within or close to tectonic contacts. NOA in highly deformed magnesium-rich meta-gabbros are associated with the opening and filling of albite-tremolite veins, associated with the syntectonic boudinage of the most competent meta-gabbros. In the meta-basalts, NOA are associated with late metamorphic, actinolite-bearing polymineralic veins cross-cutting the foliation planes. Fragments and pebbles of serpentinites, meta-gabbros and meta-basalts containing NOA are also present in colluvium, scree and alluvium resulting from erosion processes. Special attention should be paid to serpentinites and/or magnesium-rich meta-gabbros-bearing colluvium in which fibrous occurrences of tremolite regularly evolved into whitish clusters consisting of very long, easily separable, flexible and entangled fibers with a higher asbestos potential. The characterization of NOA in the COC serpentinites, meta-gabbros and meta-basalts leads us to consider them as hazardous materials. As these lithologies are very abundant within the whole structural edifice, they may be regularly impacted by development or construction work and thus require suitable monitoring.

Stratigraphic, structural, and fission track data have been integrated in order to unravel the Neogene to Quaternary tectonic evolution of northeastern Corsica. Results indicate that during early to middle Miocene the study area was affected by a rapid cooling at low temperatures accompanied by exhumation and rifting. Basin inversion occurred during the Tortonian, again followed by extension in the Messinian to early Pliocene. Compressional deformations are finally recorded by early Pliocene to Quaternary deposits. Alternating rifting and inversion events are recorded not only in northeastern Corsica but also in many peri- Tyrrhenian regions. This alternation can be explained in terms of intraplate propagation of the compressional stress related to the Africa-Europe convergence and to a discontinuous slab retreat along the Apennine subduction system. A pause in the slab retreat implies a break of the back arc extension in the upper plate, and it allows a temporary propagation of Africa-Europe compression.

The collecting mission on Corsica is part of a new exploration cycle opened in 2002 with a mission to the Maltese archipelago. The main aim is the safeguard of autochthonous crop genetic resources still present on Mediterranean islands. This new exploratory cycle follows the eight-year research accomplished for the collection of crop genetic resources from the small Italian islands. Corsica, with a surface area of 8722 km2, is the fourth largest Mediterranean island. Because of its prevalent mountain areas with a high number of small villages not readily accessible, a first exploratory mission was started in the northern part of the island in September 2003, with the southern part being visited in 2004. In our first expedition, 112 valuable landraces were collected, which belong to several species of pulses, vegetables, cereals, forages, spices and condiments. The progressive genetic erosion of crop genetic resources was clearly evident from the abandoned orchards found around all the all villages that were visited. Because of the genetic erosion risks, the building of a local genebank might help to keep alive the local agricultural traditions and resources.