A detachment fault is a low-angle normal fault that typically separates highly deformed rocks in its hanging wall from less deformed rocks in its footwall. These faults are often associated with large-scale extensional tectonics and can be linked to the formation of metamorphic core complexes. Detachment faults are significant in understanding the tectonic evolution of extensional terrains.
Source Wernicke, B. (1981). “Low-Angle Normal Faults in the Basin and Range Province: Nappe Tectonics in an Extending Orogen.” Nature, 291(5810), 645-648.