ORTHOGNEISS, MYLONITE AND NON COAXIAL DEFORMATION OF GRANITES - EXAMPLE OF THE SOUTH-ARMORICAN-SHEAR-ZONE

The deformation of two granitic massifs along a dextral wrench fault zone (the South Armorican Shear Zone) is examined at the sample and grain scales. We note that an association of continuous-discontinuous deformation mechanisms is responsible for the mylonitisation at the grain scale. The general characteristics of the deformation (strain, ellipsoid type, strain regime, non-coaxial model) and quartz fabrics measured in these mylonites at each of the mylonitisation stages described, are also discussed. © 1979.