The Versoyen region which is located at the extreme «front» of the Pennic area suggests a kind of submarine volcanism in the shape of numerous quasi-horizontal, piled sills, among several more or less loose and wet sediments. Adinoles seem to be formed at the borders of intermediary sills. The general metamorphism is discussed in this publication together with the formulation of the hypothesis of a deuteric alteration which may explain certain structures and parageneses.