Granitization

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granitization

[‚gran·əd·ə′zā·shən]
(petrology)
A process whereby various types of rock may be converted to granite or closely related material.

Granitization

 

the set of natural processes that transform solid rock of various origins (sedimentary, igneous, or metamorphic) into rock of granitoid mineral and chemical composition. At levels of intense granitization, the rock becomes plastic and capable of flowing as a result of anatexis.

Granitization generally occurs in the plutonic zones of geosynclines in strata of metamorphized rock, chiefly in the amphibolitic phase of plutonization simultaneously with or shortly after the main stages of folding. It varies in scale. In ancient Precambrian crystallized rock zones, granitization may be regional (encompassing wide areas), but in younger strata it can be local (small areas in contact with intrusions).

Granitization takes place under the influence of gaseous or liquid solutions rising from the earth’s interior and is considered as a metasomatic process associated with the addition of alkali and silica and loss of iron, magnesium, and calcium. Recent experiments prove the possibility of anatectic granitization of metamorphized rock—that is, the fusion from them of a eutectic granite melt. Anatectic granitization can occur without the addition of matter. In the USSR, widespread granitization may be observed in ancient shield regions, where there are extensively metamorphized rocks (in Karelia, Transbaikalia, and the Ukraine).

REFERENCES

Afanas’ev, G. D. “O roli granitizatsii v formirovanii granitoidnykh massivov nekotorykh skladchatykh oblastei.” Izv. ANSSSR: Ser. geol., 1951. no. 4.
Korzhinskii. D. S. “Granitizatsiia kak magmaticheskoe zame-shchenie.” Izv. AN SSSR: Ser. geol. 1952. no. 2.

V. S. KOPTEV-DVORNIKOV