Publication Date:
2009
Description:
〈b〉Morphology of the pore space in claystones – evidence from BIB/FIB ion beam sectioning and cryo-SEM observations〈/b〉〈br〉
G. Desbois, J. L. Urai, and P. A. Kukla〈br〉
eEarth, 4, 15-22, doi:10.5194/ee-4-15-2009, 2009〈br〉
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.
Print ISSN:
1815-381X
Electronic ISSN:
1815-3828
Topics:
Geosciences
