What is a migmatite in geology ?

Migmatite : definition

A migmatite is a catazonal metamorphic rock made up of a metamorphic component, often banded, with a gneissic appearance, with biotite, muscovite, andalusite, garnet... and a neoformed granite component with quartz, microcline and oligoclase. Migmatites come from rocks subjected by burial to higher and higher temperatures, which undergo partial melting, they are also called anatexites. These rocks are formed by the alternation of light levels (granitic magmatic) and dark levels (metamorphic). The clear levels are composed of quartz (gray) and feldspar (white) - Source and photo C. Nicollet.

Although classified as metamorphic rocks because they originate from the extensive fusion of rocky materials, migmatites actually represent the transition between metamorphic rock and igneous rock. They are generally closely linked to the granites with which we can observe all the transitional facies.

There are many varieties of migmatites : embrechites, nebulites, agmatites, etc...