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 ?
Project site geology is characterized by a gentle dipping, Miocene-age detachment fault juxtaposing upper plate Tertiary andesite with lower plate, Precambrian, granitic mylonite.
9:00 AGES OF GARNET GROWTH IN THE HYDE SCHOOL MARGINAL MYLONITE, ADIRONDACK LOWLANDS, NEW YORK; Nicholas M.
In this paper we report U-Pb age data on titanite from an augen granitoid mylonite in the eastern part of the DPDZ.
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.
The U-Pb titanite age obtained for the augen mylonite (TV-336) in the DPDZ demonstrates that shearing and formation of this zone occurred at 1534[+ or -]9 Ma.
At the end of the Precambrian the DPDZ was reactivated several times, as indicated by brecciated mylonite and pseudotachyllite.
Faults in this region are expressed as early shear zones that are characterized by mylonites, as well as by later more shallowly seated ductile-brittle and brittle fault zones.