M-Grades1

Metamorphic Grades I
Metamorphic rocks can be divided by the types of reactions and the pressure and temperature conditions they are subject to. while there are many levels they can be divided into several groups based on the pressure and temperature conditions present and the mineral changes these conditions induce and by the types of structures that form with in them. These can be divided into 3 broad groups:

Low Grade: Low pressure/temperature recrystallization. Incorporation of water into minerals, Reaction with chemically rich low temperature solutions. Includes conversion of clays to mica.

Medium Grade: Moderate pressure and temperature induced recrystallization. Reactions with most hot fluids, formation of garnets.

High Grade: Intense heat and or pressure. Recrystalization and mineral migrations in response to pressures and temperatures. Dewatering reactions in hydrated minerals. Reactions with magmas, Reactions along earthquake fault boundaries. Plastic flow.

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Website created: January 22, 1998 Website last updated: Noveber 18, 2000