RELATIONSHIPS BETWEEN MINERALOGY AND PORO US-MEDIUM OF THE CRAIE-TUFFEAU (PARIS BASIN, FRANCE)

55 tuffeau blocks coming from historical monuments being restored, and quarries that supply building blocks for restoration work were subjec ted to a physical and chemical characterization. Petrographically, tuf feau consists of a continuous series that is based on the ratio betwee n visible detrital minerals, in particular quartz and glauconite, and siliceous micrite. The Tuffeau de Saumur and the Tuffeau de Bourre are the end-members of this series. Tuffeau is an extremely porous rock, with an average total porosity of 44 % and an extended porosity spectr um. This is shown by a macroporosity and microporosity that, respectiv ely, are 22 and 17 % (mercury porosimetry), and an average value of 9 % for infraporosity obtained from nitrogen adsorption-desorption isoth erms: macroporosity is dominated by inter-spherules of CT opal macropo res. The remaining mineral crystals (quartz, glauconite, muscovite, sp aritic calcite) along with organism test fragments; microporosity is r elated to the compactness and arrangement style of micrite crystals. o verlapping ridges, also creates a significant proportion of this micro porous domain: infraporosity corresponds to intraleaf and intertactoid pores of clay minerals as well as to the microroughness of some other minerals such as, in particular, micrite calcite.