Temperature in the earth's crust generally decreases with depth. However, inversion of metamorphic zonation is a rather common feature of many orogenic belts. Inverted zonal sequences may be classified as continuous or discontinuous.

Geologic setting X-ray analyses Illite "crystallinity" Mineral assemblages Illite b(0)-geobarometry Summary

Continuous inverse metamorphic zonation has been explained by post-metamorphic recumbent folding, by thrusting of hot rocks over colder ones, or by shear heating on crustal thrusts
Discontinuous inverse metamorphic zonation seems to be related to major overthrusts in low-grade areas and is sometimes referred as "transported metamorphism"