metasomatism
Met`a*so"ma*tism, n. Etym: [Pref. meta- + Gr. (Geol.) Defn: An alteration in a mineral or rock mass when involving a chemical change of the substance, as of chrysolite to serpentine; -- opposed to ordinary metamorphism, as implying simply a recrystallization. -- Met`a*so*mat"ic, a.