Cataclasis

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cataclasis

[‚kad·ə′klā·səs]
(geology)
Deformation of rock by fracture and rotation of aggregates or mineral grains.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The main geological feature is an extension of the prominent Goldcorp Sidace cataclastic fault zone, and represents the major gold exploration target at Golden Loon.
Jia, "Time-dependent behavior of cataclastic rocks in a multi-loading triaxial creep test," Rock Mechanics and Rock Engineering, vol.
Lin, "Roundness of clasts in pseudotachylytes and cataclastic rocks as an indicator of frictional melting," Journal of Structural Geology, vol.
The previous K/Ar methods used three decades ago are not considered reliable since isotopic content is very susceptible to changes by hydrothermal events which are evident in the zone, and are also susceptible to be changed due to tectonism such as shearing and cataclastic events which we have documented in the petrographic analysis.
A series of NE-SW-striking shear and cataclastic fault zones are located in a belt between the largest Wiborg and Riga plutons.
Occurrence: In hydrothermal assemblages in vugs in cataclastic and mineralized dolomite carbonatite.
The mineralised bodies occur in pipes and pockets with complex shapes, with the main zone occurring within a wedge of terrigenous rocks in the upper cataclastic package.
Zhu, "The transition from brittle faulting to cataclastic flow in porous sandstones: mechanical deformation," Journal of Geophysical Research Solid Earth, vol.
(a) Close-up photo of the E-W to WNW-ESE sinistral faults showing the cataclastic core mapped along Okoy River (refer to Figure 1(c), i for the location).
The ores mainly comprise cataclastic, idiomorphic or hypidiomorphic granular, and gric textures.