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 ?
Sandstones Aptian Granites, Gneisses, Schists, Migmatites AGE DEPOSITIONAL BASIN ENVIRONMENT Quaternary Continental Niger Delta Tertiary Basin Pliocene Miocene Oligocene Continental Eocene Estuarine, Shallow marine Paleocene Shallow Marine, deltaic Upper Maastrichtian Fluvio-deltaic Anambra Cretaceous Basin Fluvio-deltaic Shallow Marine, deltaic Shallow Marine, deltaic Campanian Santonian Shallow Marine, deltaic Benue Trough Conician Middle Turonian Shallow Marine Cret.
The Bedonia Project is underlain by rocks of the Proterozoic Mount Andrews Migmatites and contains a number of magnetic features (ten current targets) that may be related to intrusive mafic rocks (the host rocks for the Nova nickelcopper discovery).
Within the Garzon Massif the plutonic bodies intrude Precambrian high grade metamorphic rocks whereas in the Upper Magdalena Valley, plutonic rocks intrude migmatites of unknown age (Alvarez, 1981; Kroonemberg, 1982; Alvarez and Linares, 1983; Velandia et al, 2001a, 2001b; Jimenez et al.
the GAC publication The Dynamics of Epeiric Seas, and the Atlas of Migmatites published by MAC), textbooks (e.
2004), these soils were developed both from Devonian sedimentary rocks (Ponta Grossa Formation) and from Precambrian rocks such as subalcaline granites, syenites, and migmatites.
This atlas of migmatites, heterogeneous rocks often found in continental crusts, is designed for geologists and mineralogists who need a reference for identifying and classifying these substances in the field.
The Vijayan Complex rocks consists of mainly granitic gneisses, hornblende biotlite gneisses, and migmatites formed under amphibolites facies, and are mainly confined to the eastern sector.
The latter often contains migmatites or small bodies of enderbitic composition, otherwise plagioclase-potassium-feldspar leucosomes and granites prevail.
The extensive Orlice-Snieznik Complex is built by orthogneisses, metagranites and migmatites with mica schists, paragneisses and phyllonites of the Stronie Group of the Lower Paleozoic and Upper Proterozoic age.
Examples are migmatites (rocks that were once partially molten and have retained part of their melt) and dykes (magma conduits that now contain solidified magma).
The oldest formations consist of pre-Birimian migmatites, gneisses and amphibolites underlying the Birimian rocks.