Thermal metamorphism, also known as contact metamorphism, occurs when rocks are heated by the intrusion of hot magma without significant deformation. This process is significant in petrology for understanding the effects of heat on mineral stability, the formation of metamorphic rocks, and the thermal history of magmatic intrusions.
Reference: Philpotts, A. R., & Ague, J. J. (2009). “Principles of Igneous and Metamorphic Petrology.” Cambridge University Press.