Cataclasite Formation Along the McConnell Thurst and Its Implications to Deformation
Bachelor of Arts
One characteristic of the McConnell thrust of the Canadian Rocky Mountains is the presence of a dark band of shaley rocks that occurs at the base of the hanging wall. These rocks are formed by initially brittle fracturing, and later ductile deformation accomplished primarily through pressure solution. I propose the that the term foliated cataclasite best describes this dark band, although pressure solution is the dominant deformation process, and the mechanisms by which it forms are operative up to 20 cm into the surrounding hanging wall and footwall rocks. Pressure solution reduces average grain size and concentrates insoluble clay and opaque oxide grains, imparting a dark color and a weak dimensional preferred fabric to the cataclasite. Deformation within the foliated cataclasite cycles between brittle and ductile processes in response to changes in porosity caused by variations in pressure solution intenSity. The dominantly ductile behavior of the cataclasite allows for further deformation along the thrust to be strain softening. and therefore, inhibits catastrophic slip events caused by the accumulation of shear strains. High carbonate volume loss from the system, yet lack of cementation, suggests that the thrust zone at Mt. Yamnuska is an open system which allows circulating fluids to remove pressure solved material. This suggests that thrust emplacement was facilitated by the ductile behavior of the cataclasite and not due to fluid overpressures along the thrust.
Van Gundy, Susan E., "Cataclasite Formation Along the McConnell Thurst and Its Implications to Deformation" (1991). Honors Papers. 10.