Fluids Changes in the chemistry of the fluids in the pore spaces of rocks also induces change. Diagenesis is not usually considered part of metamorphism although the distinction is a pretty subtle one if you ask me. One common cause of changes in the fluid chemistry is the proximity of something hot - take volcanic activity for example. The heat induces convection currents in the surrounding fluids. This form of metamorphism is known as hydrothermal alteration and is the way most metallic ore bodies formed.
Compaction produces a more closely packed arrangement of grains.
This is exmplified by the transformation of clay to slate. Recrystallization involves growth of new minerals. If the pressure is higher in one direction than the others, minerals will tend to align themselves such that the fabric formsperpendicular to this axis. A planar fabric is known as a foliation while alignment of crystals causes a lineation. Increasing metamorphism resultsin different types of foliation.