migmatite

thumb|Ptygmatic folding in migmatite on Naissaar Island, Estonia thumb|Migmatite on the coast of Saaremaa, Estonia thumb|Intricately-folded migmatite from near Geirangerfjord, Norway

Migmatite is a composite rock found in medium and high-grade metamorphic environments, commonly within Precambrian cratonic blocks. It consists of two or more constituents often layered repetitively: one layer is an older metamorphic rock that was reconstituted subsequently by partial melting ("paleosome"), while the alternate layer has a pegmatitic, aplitic, granitic or generally plutonic appearance ("neosome"). Commonly, migmatites occur below deformed metamorphic rocks that represent the base of eroded mountain chains.