met·a·so·ma·tism 
(mĕt′ə-sōmə-tĭz′əm) also met·a·so·ma·to·sis (-sō′mə-tōsĭs)
(mĕt′ə-sōmə-tĭz′əm) also met·a·so·ma·to·sis (-sō′mə-tōsĭs)n.
The process by which the chemical composition of a rock is changed by interaction with fluids; replacement of one mineral by another without melting.
met′a·so·matic (-mătĭk) adj.
met′a·so·mati·cal·ly adv.