Finite strain analysis and significance of ultramafic lenses from the Western Maures (SE France). Geodynamic implications.

The first structural study of ultramafic lenses from the Variscan Maures ma ssif allows definition of the finite strain ellipsoid in relation to a tect onic event later than the Visean nappe tectonics and prior to the Namurian late-orogenic extension, which are characterized by a NW-SE-striking stretc hing lineation transverse to the belt. The ultramafites present a longitudi nal NNE-SSW stretching lineation, associated with a sub-vertical flattening plate and essentially symmetrical structures. P-T conditions of deformatio n can be compared with those of the regional metamorphism. The en echelon s tructure of serpentinite sites can be related to a ductile strike-slip faul t. (C) 2000 Academie des sciences/Editions scientifiques et medicales Elsev ier SAS.