[S-CG56] Dynamics in mobile belts

[SCG56-P10] Surface topography of grain boundary cracks in a granitic rock

*Tohru Watanabe¹, Kenta Yoshida² (1.Faculty of Sustainable Design, University of Toyama, 2.JAMSTEC)

Keywords:microcrack, X-ray CT, FIB-SEM, asperity

Physical properties of rocks are strongly affected by cracks, and their pressure dependence is governed by the closure of cracks under pressure. Cracks have rough surfaces and asperities come into contact under pressure. Physical properties under pressure are governed by the surface topography of cracks. Although the surface topography of macroscopic fractures (> cm) has been investigated by using profilometers, that of microcracks (< mm) is still poorly understood. Observations on thin sections and polished surfaces provide the surface topography only in a cross-section. We tried to study the surface structure of grain boundary cracks in Aji granite (Kagawa Pref.) by using an X-ray nano-focus CT and a dual-beam focused ion beam-SEM (FIB-SEM). A granitic rock sample was heated to 630°C to make grain boundary wider. A grayscale image was binarized to yield a black and white image, and then the asperity height and aperture were measured. Comparisons of results with X-ray CT and FIB-SEM will be presented in our poster.