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The Argentera Massif in the western Alps is made of up two medium–high-grade metamorphic complexes of Variscan age. They are separated by a regional-scale northwest-trending shear zone, the Ferrie`re–Mollie`res Line, which consists of low-grade mylonitic rocks. Muscovite-bearing mylonitic leucogranites crop out as subvertical northwest-trending intrusions, in the northern portion of the shear zone. A Rb/Sr muscovite–wr age of 327±3 Ma on foliated leucogranite gives a lower limit for the age of mylonitic deformation for which kinematic indicators indicate a dextral sense of shear. This strike-slip tectonics is compatible with the extensional regime that occurred during Carboniferous in the whole western Europe. To cite this article: G. Musumeci, F. Colombo, C. R. Geoscience 334 (2002) 213–220. [Copyright &y& Elsevier]