What is the process called that leads to localized changes in rock due to igneous intrusion?

The process that leads to localized changes in rock due to igneous intrusion is known as contact metamorphism. When molten magma from within the Earth intrudes into cooler surrounding rocks, the intense heat from the magma alters the mineral structure and composition of those surrounding rocks without the rocks undergoing melting themselves. This heat and any associated fluids cause changes that can manifest in various ways, such as recrystallization, the development of new minerals, or changes in texture.

Contact metamorphism typically occurs in a relatively small spatial area, close to the intrusion, resulting in a distinct metamorphic zone with characteristics that differ from the original rock. This is in contrast to other processes, such as cooling metamorphism, where changes occur primarily due to the temperature decrease over time, or diffusion, which refers to the movement of atoms or molecules from an area of high concentration to an area of low concentration. Subduction, on the other hand, involves the process of one tectonic plate moving under another and doesn't relate directly to the localized changes caused by the heat from an igneous intrusion. Thus, contact metamorphism is the correct term for this specific geological process.