Migmatite

migmatite

Rock composed of a metamorphic host material that is streaked or veined with granite; the name means “mixed rock.” Many migmatites probably represent partial fusion of the metamorphic host; some components of the rock are fused and gather to produce the streaks of granite. Migmatite also can form near large intrusions of granite when some of the magma is injected into neighbouring metamorphic rocks.

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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.

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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.