Characteristics of micro transfer paths and diffusion phenomena in the matrix of deep crystalline rock

Ishibashi, Masayuki; Sasao, Eiji; Hama, Katsuhiro

Matrix diffusion is one of the important phenomena for safety assessment of radioactive waste disposal because it has an effect of retarding the mass transport in crystalline rocks. Although there is not enough knowledge on the matrix diffusion in unaltered (intact) rocks around fractures. Intact granitic rocks around fractures are affected by primary alteration related to hydrothermal fluid resulting from crystallization of granitic magma. Therefore, detailed observations were carried out to clarify the effects of primary alteration focused on the intact granite around fractures sampled from the MIU, central Japan. The results of observation provide that the micropores are formed in plagioclases affected by primary alteration and have the potential of acting as matrix diffusion paths. This is indicating the possibility that intact granitic rock around fractures in an orogenic belt such as Japan have also the retardation functions due to matrix diffusion.