Transcurrent strain partitioning along a suture zone in the Maures massif (France): Result of eastern indenter tectonics in European Variscides?

Abstract

ABSTARCT The ultramafic-rich shear zone from the Variscan Maures massif is a part of a linear suture zone that extends for 1000 km from Sardinia to the Bohemian massif. Multiscale analyses of ultramafic porphyroclasts and associated mantle structures, including analysis of ductile and associated ductile-brittle deformation, demonstrate the strong overprinting of this suture zone by wrench tectonics during continental collision. For 30 km along the ultramafic-rich shear zone, noncoaxial strain indicates at all scales a major sinistral transcurrent shearing with a heterogeneous, partitioned, and progressive strain. This transpressional stage occurs during the mid-Visean exhumation of crustal nappes. In this chapter we point out a model of oblique collision in this Variscan range resulting from eastern indenter tectonics in the European Variscides. The implicate microplates, as well as the irregular margin of continents, were strongly deformed during the convergence and diachronous collision between Baltica-Laurentia and Gondwana. The ultramafic-rich shear zone from the Variscan Maures massif is a well-defined example of an unrooted lithospheric suture zone in a collisional belt, overprinted by transcurrent tectonics after continental subduction and prior to late orogenic extension.