Mylonite


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mylonite

[′mī·lə‚nīt]
(petrology)
A hard, coherent, often glassy-looking rock that has suffered extreme mechanical deformation and granulation but has remained chemically unaltered; appearance is flinty, banded, or streaked, but the nature of the parent rock is easily recognized.

Mylonite

 

finely ground, crushed rock formed by the movement of rock masses along the surface of tectonic faults. As a result of great pressure, the rocks (granite, gneiss, schists, quartzite) are crushed and ground into a compact state. Microscopic analysis makes possible the identification of finely ground mica flakes and minute quartz and feldspar fragments in the finely pulverized mass, which is made up of the softer minerals of the primary rock and sometimes such new formations as sericite and zoisite. Unlike cataclasis, mylonitization represents the final stage in the crushing of rock into microscopic form. Mylonite zones are located along the major regional thrust faults in the Urals, Tien-Shan, the Caucasus, and the Altai. These zones are several hundred meters wide and extend several dozen kilometers.

REFERENCE

Polovinkina, Iu. I. Struktury i tekstury izverzhennykh i metamorficheskikh porod, vol. 2, part 2. Moscow, 1966.
References in periodicals archive ?
The striped mylonite structure consists of continuous bands of mostly recrystallized grains, this plane attitude is N40[degrees]W/60[degrees]NE approximately parallel to the foliation and connected with the shear plane.
Ductile and brittle fault fabrics indicate initial ductile dextral shearing of Fredericton, Miramichi, and granitic rocks followed by brittle faulting of mylonite, granite, and sedimentary rocks, perhaps with dominantly vertical separation.
SAMPLE DESCRIPTION The selected sample (TV-336) is an augen granitoid mylonite from the Tverecius-336 drill core, located in the eastern part of the DPDZ close to the Belarus border (Fig.
Six rock types can be distinguished, with the following proportions: granite (38%), mylonite (21%), quartzite (16%), metapelite (13%), quartz (10%) and augen gneiss (2%).
The Central Metasedimentary Belt Boundary Zone (CMBBZ) separates the CMB from the Central Gneiss Belt (CGB) to the west; its eastern border is defined by the Carthage-Colton mylonite zone and Labelle shear zone.
Some of the boundaries have character of mylonite zone /1/ (contact rocks of the Stronie Group and orthogneisse of Orlice-Snieznik Complex in the Velka Morava valley), tectonic contacts, dislocation /2/ (Nyznerov on north of Velke Vrbno Unit) or thrust /3/ (Ramzova).
Brittle deformation of hornblende in a mylonite; A direct geometrical analogue of ductile deformation by translation gliding.
9:00 AGES OF GARNET GROWTH IN THE HYDE SCHOOL MARGINAL MYLONITE, ADIRONDACK LOWLANDS, NEW YORK; Nicholas M.
It comprises carbonaceous mylonite which ranges from broken rubble to silicified graphitic schists.