Fault rocks at different crustal depths generate different fault structures and tectonites mostly depending on lithology, fluid flow and temperature. In this note we address the fault zone development and deformation mechanisms that occur in carbonate lithologies at different crustal levels. We compare faults exhumed near the brittleductile transition in the Helvetic Nappes in theAlps and similar faults from the upper crust in the Gran Sasso area in the Central Appenines. We observe the different role of deformation processes at different depth and lithology and assess the tendency for localization at the Brittle Ductile Transition.