Peeling of Sheared Mudstones: Insights into the Smectite to Illite Transformation

The microstructural characteristics of a shear zone developed in Plio-Pleistocene mudstones of the Southern Apennines have been analysed by means of XRD, SEM, optical microscope observation and a consolidation test. XRD analyses indicate that the wall rock contains mixed layer illite/smectite while the fault gauge contains illite only. The distribution patterns of smectitic and illitic mudstones is analysed thanks to a simple peeling technique that allows observation with optical microscope and SEM. The consolidation test provides indications on the depth at which deformation occurred.