eEarth www.electronic-earth.net 1815-381X 1815-3828 4 1 2009 10.5194/ee-4-15-2009 http://www.electronic-earth.net/4/15/2009/ http://www.electronic-earth.net/4/15/2009/ee-4-15-2009.html http://www.electronic-earth.net/4/15/2009/ee-4-15-2009.pdf 15 22 2009-07-08 Morphology of the pore space in claystones – evidence from BIB/FIB ion beam sectioning and cryo-SEM observations G. Desbois g.desbois@ged.rwth-aachen.de J. L. Urai P. A. Kukla Geologie – Endogene Dynamik, RWTH Aachen University, Lochnerstr. 4–20, 52056 Aachen, Germany Geological Institute, RWTH Aachen University, Wüllnerstr. 2, 52062 Aachen, Germany 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. 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