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 ?
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.
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).
Heteregeneous Deformation, foliation development and metamorphic processes in a polyphase mylonite.
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.
Further the southwestern limb of the Muzaffarabad anticline physically shows fresh fault breccia, mylonite and gouge line and their downwardflow revealing the recent active nature ofthis thrusted anticline.
Structural analysis of the Creignish Hills mylonite zone, Cape Breton Island, Nova Scotia; implications for Neoproterozoic core complex development along the northern Gondwanan margin?
In the west, the Strazek Moldanubicum is demarcated by the Pribyslav mylonite zone; in the northeast the Strazek Moldanubicum joins the Nasavrky Massif, or the southernmost spur of the Hlinsko zone and the Svratka crystalline complex.
It is accompanied by tectonically deformed rocks forming cataclasite, mylonite or breccia zones.
This rock unit, along with a thick sequence of supracrustals, forms the hanging wall to a quartz sericite altered mylonite zone.
The evident unconformable contacts in Timber Brook and in the lower reaches of North River, where windows through the Carboniferous sequence reveal underlying units of diorite, granodiorite, gneiss and mylonite, lie to the east of the main block of thrusted rocks, and appear to be unrelated to the thrust contacts identified here.