Evidence for a ductile strike-slip fault in the Porquerolles Island (Var, France) and its tectonic implications on the Upper Palaeozoic tectonics of the Variscan Maures Massif

A new geological map of the Palaeozoic units from the Porquerolles Island provides evidence for two main units joined along a north-south-trending shear zone: a western unit of schist, sandstone and microconglomerates, an eastern unit of schist including calcareous rocks, metabasite and various types of mineralisations. The shear zone has experienced a main strike-slip, sinistral movement in a ductile regime, and a late westward normal movement from ductile to brittle regimes. It crosscuts an early thrust fault, marked by penetrative syn-metamorphic deformation and the abundance of quartz rods. According to geometrical relationships, the regional conic fold is interpreted as a large-scale dragging of foliation related to strike-slip faulting. Combined folding and wrenching point out a main transpressional tectonics related to the continental collision dated Middle Visean in the central and eastern parts of the Variscan Mantes massif. (C) 2003 Academie des sciences. Publie par Elsevier SAS. Tous droits reserves.