Fig. 3

a Photograph of a slickenside surface (top view). b On such a surface, note the dark, polished parts and the bright, ragged parts, being respectively treads and risers of the slickenside steps (Laurich 2015). The arrow gives the movement direction of the missing block. c Photograph of b combined with a SEM-EDX Ca mapping picture showing the occurrence of calcite at the risers. This suggests that the risers are in the stress-releasing zones, where Ca precipitation took place. d Side view on a micrometer-thin shear zone in a broken sample. Note that the bedding foliation is continuous up to the thin shear zone. e Is an inset of d illustrating that the shear zone width can be as small as only 10th of nm