Schematic structural and petrologic sketch summarizing the formation mechanisms of amphibole-chlorite schists in shear zones in the Marine de Giottani metagabbros. The deformation in metagabbros that initially localizes around serpentinite clasts is enhanced by metamorphic reactions implied by fluid-assisted mechanical mixing and metasomatism between those two end-members. Deformation, fluids and metamorphism create and maintain a positive feedback loop that allows rock weakening within the newly formed amphibole-bearing shear zones.