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Concept
Deformation mechanism
Summary
A deformation mechanism, in geology, is a process occurring at a microscopic scale that is responsible for changes in a material's internal structure, shape and volume. The process involves planar discontinuity and/or displacement of atoms from their original position within a crystal lattice structure. These small changes are preserved in various microstructures of materials such as rocks, metals and plastics, and can be studied in depth using optical or digital microscopy.
Deformation mechanisms are commonly characterized as brittle, ductile, and brittle-ductile. The driving mechanism responsible is an interplay between internal (e.g. composition, grain size and lattice-preferred orientation) and external (e.g. temperature and fluid pressure) factors. These mechanisms produce a range of micro-structures studied in rocks to constrain the conditions, rheology, dynamics, and motions of tectonic events. More than one mechanism may be active under a given set of conditions and some mechanisms can develop independently. Detailed microstructure analysis can be used to define the conditions and timing under which individual deformation mechanisms dominate for some materials. Common deformation mechanisms processes include:
Fracturing
Cataclastic flow
Diffusive mass transfer
Grain-boundary sliding
Dislocation creep
Dynamic recrystallization (recovery)
Fracturing
Fracturing is a brittle deformation process that creates permanent linear breaks, that are not accompanied by displacement within materials. These linear breaks or openings can be independent or interconnected. For fracturing to occur, the ultimate strength of the materials need to be exceeded to a point where the material ruptures. Rupturing is aided by the accumulations of high differential stress (the difference between the maximum and minimum stress acting on the object). Most fracture grow into faults. However, the term fault is only used when the fracture plane accommodate some degree of movement. Fracturing can happen across all scales, from microfractures to macroscopic fractures and joints in the rocks.
Official source
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