Fig. 5
From: Timing and conditions of brittle faulting on the Silltal-Brenner Fault Zone, Eastern Alps (Austria)
Selected SEM and TEM images from Sample BF2, together with EDS scans indicating the qualitative chemical composition. These scans demonstrate that the grains analysed must correspond to the 2M1 illite/muscovite polytype, as it is the only K-bearing phase recognized in the quantitative XRD analysis. a SEM secondary electron image of the sampled “whole-rock gouge” as collected, showing large (>20 μm) abraded grains in a finer grained matrix interpreted to have developed by comminution of larger muscovite protolith grains. b TEM image of the <0.1 μm size fraction, showing the irregular pseudohexagonal platelet morphology of grains typical of the 2M1 polytype. Many grains have diffuse, irregular boundaries, which are typical of abraded grains (either initial protolith or older authigenic grains), but some edges are straight (marked by arrows) and more indicative of authigenic illite