Keep in mind that they often work together to alter the parent rock into a metamorphic rock. As temperature and pressure rise, bonds holding minerals together begin to break and reform. So, recrystallization leads to a change in the texture of a rock, not to a change in composition. An increase in temperature and pressure on a rock composed of a variety of minerals, or of a mineral of complex composition will cause bonds holding those minerals together to break and then reform into totally different, new minerals. This process is called neomorphism, and it can dramatically alter the composition of the original, parent rock.
Textural changes can also occur during neomorphism.
Common metamorphic minerals formed in this way include garnet, chlorite, tourmaline, serpentine, muscovite mica, and talc. This is called metasomatism, and it can occur as hydrothermal fluids are extruded from a body of magma into the surrounding rock, or as groundwater circulates close to a body of magma and then moves upward into overlying rock. This metamorphic process is directly related to igneous activity, so it is commonly associated with subduction and divergent plate tectonic boundaries where magma is abundant. Rich deposits of copper and iron have resulted from metasomatism, so this process is of major interest to mining companies. Return to the top of this page.