Box 2 Properties of Slip Bands‌

Scanning electron microscopy analyses of slip band infill along three transects showed strong peaks in Fe-rich mineral cement (goethite/hematite mixture) and a corresponding decrease in Si- and O2-rich mineral cement. The X-ray diffraction analyses of the samples with a whitish infill showed a strong peak corresponding to amorphous silica, which is believed to be opal. Opal as well as goethite/hematite infill markedly reduce the porosity and permeability of slip bands. Permeability values of slip bands partially filled with hematite/goethite cement were computed using thin-section image analyses in conjunction with a computational rock physics-based algorithm called PETS (permeability estimation from thin sections) and the Lattice-Boltzmann method (Keehm et al., 2004). Slip band permeabilities are commonly expressed in millidarcies (mD) and are estimated to be in the range of 7×10-6 mD to 3.9 mD. Partially filled slip band permeabilities range from 2.8 mD to 150 mD, whereas open slip surfaces have permeabilities as high as 5×106 mD.

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