A metamorphic reaction is a chemical reaction that takes place during the geological process of metamorphism wherein one assemblage of minerals is transformed into a second assemblage which is stable under the new temperature/pressure conditions resulting in the final stable state of the observed metamorphic rock.
Examples would include the production of talc under varied metamorphic conditions:
serpentine + carbon dioxide → talc + magnesite + water chlorite + quartz → kyanite + talc + waterReferences
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