Migmatite

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migmatite

[′mig·mə‚tīt]
(petrology)
A mixed rock exhibiting crystalline textures in which a truly metamorphic component is streaked and mixed with obviously once-molten material of a more or less granitic character.

Migmatite

 

a rock consisting of metamorphic enclosing material with veins of granite. It is formed when liquid strata of granitic magma penetrate along the cleavage of metamorphic rocks. The granitic magma may form through the partial melting (anatexis) of metamorphic rocks under conditions of deep burial (regional metamorphism), when the molten rock is forced out of the unmelted metamorphic remainder. Many Precambrian migmatites were formed under such conditions. Migmatites located near large intrusive bodies of granitoids arose when granitic melt was injected into adjacent metamorphic rocks (injection gneiss). Migmatite is commonly found in ancient granite-gneiss complexes.

References in periodicals archive ?
Geochemically, synorogenic granites show I-type characteristics and their genesis is related to granulitic metamorphism (Niin 1997), although some authors have treated them together with late-orogenic migmatite granites (Puura et al.
We analyzed outcrop and drill core sections through stromatic migmatites (with parallel melt veins) in South Finland, Labrador, and the Estonian crystalline basement and found power law distributions in all cases (see Fig.
Favorable types include: (a) granite which contains abundant small flakes of dark mica, and (b) granite which apparently originated by the conversion of ancient sedimentary rocks of complex composition (sometimes called granitized rocks, migmatites, and some of the hybrid granites).
geochemical surveys) was carried out within the paragneisses, migmatites, pegmatites, granites and granodiorites underlying most of the Company's ground position.
The Yaounde series consist of strongly deformed meta-sedimentary rocks and migmatites (Nzenti et al, 1988)
The crystalline rocks within the DPDZ are granulites, biotite granites and migmatites, the latter consisting of amphibole-plagioclase palaeo- and mesosomes, and plagioclase-quartz-biotite[+ or -]microcline[+ or -]amphibole neosomes.
Kriegsman and Nystrom present a review of melt segregation rates in migmatites along with a companion paper outlining a detailed case study.
Oyawoye (1972) observed that the Basement Complex consists mainly of quartzofeldspathic migmatites and gneisses with occasional quartzites, marbles.
The composition of rocks and their metamorphic grade change rapidly from granulitic or high-grade amphibolitic in the PPZ to mainly medium-grade amphibolitic metasediments and intermediate to felsic metavolcanics, migmatites, and late-orogenic microcline granites in the Tallinn and Alutaguse zones.
The host rocks of the silver mineralization are mainly Archean migmatites and gneisses and Middle Proterozoic rhyolite, andesite porphyry, and volcanic breccia, which have been intruded by Messozoic granitic stocks.
The migmatite-gneiss complex is Neo-Proterozoic to Meso-Archean (542Ma-3200Ma) in age and composed of migmatites and gneisses.