The metamorphic rock that forms during extreme regional metamorphism that caused the rock to partially melt is called "migmatite". Migmatite is a rock at the frontier between igneous and metamorphic rocks, and it forms under extreme temperature conditions during prograde metamorphism. As the rock heats up and undergoes increasing pressure, it begins to partially melt. This cause the mineral crystals in the rock to recrystallize and fuse with the melted portions, resulting in the banded appearance of migmatite. Other examples of metamorphic rocks that can form from regional metamorphism include gneiss, schist, slate, and marble.