faillites

Faultites are lithified fault-zone rocks that record brittle deformation along faults. The term is used in some geological literature as a broad category for rocks formed by fracturing, grinding, and deformation of wall rocks within fault zones. In English, more precise terms such as fault gouge, fault breccia, cataclasite, and, for more metamorphosed material, mylonite are often preferred. Thus faultites can function as an umbrella name for various fault-related rocks, though authors may reserve it for specific textures or stages of faulting.

Formation and textures vary with所 fault history and conditions. Faultites develop through repeated rupture and comminution, producing a matrix of fine-grained powder and larger fragments that may be cemented by mineral precipitation. Textures range from very fine, clay-rich gouge to coarse, angular fault breccias, and they may display foliations or lineations inherited from slip. In some settings, pockets of frictional melting create glassy material known as pseudotachylyte, which can be included within faultites.

Interpretation and significance are tied to the rock’s microstructure. Analyzing grain size distribution, mineralogy, and fabric in faultites helps reconstruct slip history, fluid activity, and temperature conditions during faulting. They provide insights into the architecture of fault zones and the mechanical behavior of faults during earthquakes and steady slip.

See also: fault rocks, gouge, breccia, cataclasite, mylonite, pseudotachylyte.