Meaning of metasomatism

met•a•so•ma•tism

Pronunciation: (met"u-sō'mu-tiz"um), [key]
— n. Geol.
  1. the series of metamorphic processes whereby chemical changes occur in minerals or rocks as a result of the introduction of material, often in hot aqueous solutions, from external sources.
  2. replacement (def. 4).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.