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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.



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.


Polovinkina, Iu. I. Struktury i tekstury izverzhennykh i metamorficheskikh porod, vol. 2, part 2. Moscow, 1966.
References in periodicals archive ?
Although it was not specifically observed, it is inferred to be a fault contact due to the presence of mylonitic foliation (N10[degrees]E/90[degrees]), which is defined by quartz and plagioclase porphyroclasts in the hornblende schists (Figure 2d).
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.
BURNT WELL PROPERTY, the regional geological setting is a major detachment fault (called the "Bullard Detachment Fault") separating an upper plate of Tertiary siltstone / sandstone and conglomerate from a lower plate of Precambrian mylonitic gneiss.
The structures which host the uranium mineralization appear to be controlled by the fault splays and dislocation caused by cross cutting open faults and mylonitic fault zones associated with the regional Grease River fault system.
5 million) indicating significant gold mineralization is hosted by sheared and mylonitic, fine-grained sediments in contact with basic volcanics.
Bjorkramyran Deposit - Metamict zircon-uraninite mineralisation is associated with silicified mylonitic material in an en-echelon series of three, south of east trending portions of a fault zone cutting the Revsund Granite.
Strike-slip motion on the northeast-striking faults has also produced foliation in adjacent rocks which varies with proximity to shear zones from none to mylonitic.
The first drill hole for the winter program, BLK001, went directly into basement and intersected intensely mylonitic graphitic pelites.
Drill hole RO-02 cut a mylonitic shear below defined resources at Lac Fortune.
1992) noted the varied metamorphic and mylonitic rocks in the basement blocks on Isle Madame and Green Island, and suggested that they were derived from the Meguma terrane.
It is characterized by gold-bearing quartz veins adjacent to the eastern margin of a mylonitic zone.