Evidence of recent fluid circulation in crystalline rocks. An analytic approach on fracture filling minerals and paleo-fluids

This study has been realized in three sites: Andra-Vienne, Peny and Bernardan mines, north west of the Massif Central in France. The study of the crystallization in the fractures showed that nearly the whole of the fillings results of paleo-circulations bonded to two geo-dynamical major events:the Hercynian orogenesis and the mesozoic distension. Recent events present limited bulks. They correspond to kaolinite and calcite crystallisation. They are induced by the galleries and boring opening: amorphous iron hydroxides, uranium and gypsum sulfates. (A.L.B.)