%0 Journal Article
%T Morphology of the pore space in claystones ¨C evidence from BIB/FIB ion beam sectioning and cryo-SEM observations
%A G. Desbois
%A J. L. Urai
%A P. A. Kukla
%J eEarth (eE) & Discussions (eED)
%D 2009
%I 
%R 10.5194/ee-4-15-2009
%X The morphology of pore space has a strong effect on mechanical and transport properties of mudrocks and clay-rich fault gouge, but its characterization has been mostly indirect. We report on a study of Boom clay from a proposed disposal site of radioactive waste (Mol site, Belgium) using high resolution SEM at cryogenic temperature, with ion beam cross-sectioning to prepare smooth, damage free surfaces. Pores commonly have crack-like tips, preferred orientation parallel to bedding and power law size distribution. We define a number of pore types depending on shape and location in the microstructure: large jagged pores in strain shadows of clastic grains, high aspect ratio pores between similarly oriented phyllosilicate grains and crescent-shaped pores in saddle reefs of folded phyllosilicates. 3-D reconstruction by serial cross-sectioning shows 3-D connectivity of the pore space. These findings offer a new insight into the morphology of pores down to nano-scale in comparison to traditional pore size distributions calculated from mercury Injection experiments, explain slaking of clays by successive wetting and drying and provide the basis for microstructure-based models of transport in clays.
%U http://www.electronic-earth.net/4/15/2009/ee-4-15-2009.html