Formation of banded gneisses by deformation of igneous rocks

The development of finely layered gneisses by progressive deformation of a variety of granitoid intrusions, leucogabbroa, anorthosites, and basic and intermediate volcanic rocks is described and illustrated.Gneissose layering developed by the tectonic distortion of: magmatic and volcanic layering; particles such as pillow lavas, igneous crystals, and rock fragments in volcanic and plutonic breccias; patchy igneous textures; and vein networks. The products of extreme deformation during amphibolite facies metamorphism are uniformly layered gneisses.