1Structural Geology, Tectonics and Geomechanics, RWTH Aachen University, Lochnerstrasse 4–20, 52056 Aachen, Germany
2Univ. Grenoble Alpes, CNRS, Grenoble INP, 3SR, 1270 Rue de la Piscine, 38610 Gières, France
Received: 12 Sep 2016 – Discussion started: 04 Oct 2016
Abstract. The macroscopic description of deformation and fluid flow in mudrocks can be improved by a better understanding of microphysical deformation mechanisms. Here we use a combination of scanning electron microscopy (SEM) and broad ion beam (BIB) polishing to study the evolution of microstructure in samples of triaxially deformed Callovo–Oxfordian Clay. Digital image correlation (DIC) was used to measure strain field in the samples and as a guide to select regions of interest in the sample for BIB–SEM analysis. Microstructures show evidence for dominantly cataclastic and minor crystal plastic mechanisms (intergranular, transgranular, intragranular cracking, grain rotation, clay particle bending) down to the nanometre scale. At low strain, the dilatant fabric contains individually recognisable open fractures, while at high strain the reworked clay gouge also contains broken non-clay grains and smaller pores than the undeformed material, resealing the initial fracture porosity.
Revised: 08 Feb 2017 – Accepted: 17 Feb 2017 – Published: 09 Mar 2017
Desbois, G., Höhne, N., Urai, J. L., Bésuelle, P., and Viggiani, G.: Deformation in cemented mudrock (Callovo–Oxfordian Clay) by microcracking, granular flow and phyllosilicate plasticity: insights from triaxial deformation, broad ion beam polishing and scanning electron microscopy, Solid Earth, 8, 291-305, doi:10.5194/se-8-291-2017, 2017.