Types of metamorphism

TYPES OF METAMORPHISM

Regional Metamorphism
- Corresponds to progressive changes, increases, in Temperature & Pressure, due to burial.
- Commonly this type of metamorphism is associated with orogenic events and processes.
- Regionally metamorphosed rocks occur in very large belts, 10 - 100's km wide by 100 - 1000's km long.
  - Within each belt will be preserved at least one thermal axis, representing the maximum temperature of metamorphism within the belt.
  - Temperatures will increase towards the thermal axis.
  - Associated granitic and/or ultramafic masses intruded into the terranes generally, but not always near the thermal axis.
Contact Metamorphism
- Recrystallization, production of metamorphic mineral assemblages, within the contact aureole surrounding an intrusive body
- Generally held that P remains constant and metamorphism results from temperature increase, due to conduction of heat away from intrusive.
Pyro Metamorphism
- Recrystallization at high temperature of xenolith fragments in volcanic rocks or small intrusions;
- Melting of the xenolith may occur.
Hydrothermal Metamorphism
- Recrystallization associated with and influenced by a hydrothermal solution.
Cataclastic Metamorphism
- Crushing or grinding of rocks as a result of fault movement.