Cataclasis


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cataclasis

[‚kad·ə′klā·səs]
(geology)
Deformation of rock by fracture and rotation of aggregates or mineral grains.

Cataclasis

 

the deformation and crushing of minerals within rock during tectonic movements. Cataclasis occurs chiefly along and near tectonic ruptures (faults, displacements, overthrusts), where the relative shifts of rock sections have caused the grinding of minerals. Weak cataclasis can be ascertained only by examining a thin section of a crystal under polarized light and is shown by an “undulating decline,” notably in quartz crystals. Under the same conditions, stronger cataclasis results in a “mosaic decline,” indicating that various sections of the crystal have acquired through deformation a different orientation of the optic axes. Still stronger cataclasis is exhibited in the crushing of individual granules (granulation), which results in a “concrete” structure (larger angular or circular granules remain among the finely crushed material). The rock is transformed into mylonite, a compact, frequently silicified mass consisting of minute fusiform, lenticular, and flaky mineral fragments difficult to distinguish under a microscope.

In soft rocks, cataclasis may be seen in the formation of “clays of crushing” and “rock flour.” In the process of cataclasis, feldspars, micas, calcite, and certain other minerals are bent and split along the cleavage planes.

The zones that have undergone cataclasis are permeable to the movement of mineral aqueous solutions, including ore-bearing ones, and this causes the accumulation of various ores. The structure of rock that has undergone cataclasis is termed cata-clastic.

REFERENCE

Eliseev, N. A. Metamorfizm. Leningrad, 1959.

V. V. BELOUSOV

References in periodicals archive ?
It may undergo mylonitization, cataclasis, brecciation, geochemical alteration, and development of clay-rich fault gouge.
1972) mencionaron de forma general que estas rocas sufrieron fuerte cataclasis y metamorfismo retrogrado, no describieron ni caracterizaron la recristalizacion ni la deformacion diferencial que sufrieron estas rocas, ya que en el area pueden ser encontrados gneis, gneis protomiloniticos.
The mineralization appears to be located at the intersection of two regional structural trends where deformation has produced intense cataclasis and brecciation.
Un evento orogenico evidenciado por la esquistosidad; un evento ductil anterior a la formacion de la aureola, un evento termico sobreimpuesto de edad Cretacico asociado a la intrusion de la Granodiorita de Mariquita y finalmente, un evento fragil con cataclasis.
Graves (1990) further documented the variety of rock types and noted the high degree of epidotization, quartz veining, and cataclasis, as well as the presence of mylonitic rocks.
Microscopicamente, en algunas zonas de cizalla se pueden ver bordes transicionales entre los metagabros no afectados por cataclasis hasta ultra cataclasitas derivadas de los metagabros (Figura 4).
Las microestructuras generadas dentro del campo fragil en la plagioclasa, por efecto de cataclasis, son: varios tipos de microfracturas (Figura 9), microfallas y maclas de deformacion (Figura 8).
The systematic presence of thorough cataclasis of the older, deeper assemblage, particularly on its faulted boundaries.
El termino "pseudotaquilita relacionada a falla" es definido como una "roca en vetillas afaniticas, densa, color cafe oscuro, formada a partir de cataclasis extrema y/o fusion parcial dentro de una zona de falla" (Lin, 2008).
In contrast, only minor cataclasis and brecciation were found in granite, granitic mylonite, and phyilonite in the Kellyland ductile shear zone.