Cataclasite

The original classification scheme by Sibson classifies them by their proportion of fine-grained matrix to angular fragments.

Cataclasites are different from mylonites, another type of fault rock, that is classified by the presence of a schistosity formed through ductile deformation methods.

[6] According to Sibson's 1975 classification scheme, these would be classified as mylonites[1] although it was proven experimentally that some cataclastic mechanisms can form cataclasites with an oriented foliation solely due to brittle deformation.

[6] In a modification to the original definitions, the foliated fault rock would be still considered a cataclasite because it was created by cataclastic mechanisms.

[2] Comminution, along with frictional sliding and grain boundary rotation can allow a rock to macroscopically flow over a wide brittle zone in the crust.

Cataclasite under a petrographic microscope . The rock in part of the Malm Formation of the Helvetic nappes ; sample found in a landslide near Engelberg in the Swiss Alps .
Thin section image of a cataclasite in both plane polarized light (right) and crossed polarized light (left). Contact between highly fractured wall rock (right) and clast supported cataclasite (left) is outlined in red. This rock is from the San Andreas Fault at Elizabeth Lake, California.
Thin section image of a foliated cataclasite in both plane polarized light (right) and crossed polarized light (left). The banding in this cataclasite is defined by grain size and ratio of clasts to matrix. This rock is from the San Andreas Fault at Elizabeth Lake, California.