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Fig. 10. Photomicrographs showing: (a) flaking and rotation of quartz clasts, and open fractures that follow grain boundary contacts near HW Fracture 3 (Fig. 6, Sample BT-99); (b) a zone of cataclasis and an opening-mode microfracture in the footwall mixed zone and the fault core contact (Fig. 5, Sample BT-74), viewed in plane polarized light; (c) indistinct micro-scale layering within the internal fault core where deformation is localized in narrow cataclastic bands of aligned angular shards and phenocrysts, with an opening mode microfracture that parallels cataclastic layering (Fig. 5, Sample BT-82); (d) sintering in the hanging-wall zone at approximately 0.5 m west of the Chalk Cove fault (Fig. 5, Sample BT-82); (e) locally decreased grain size (zone of comminution) within the central fault zone core (Fig. 5, Sample BT-85). Deformation within the fault-zone core includes dilational microfractures that parallel bands of comminuted host rock. Note how the extension fracture locally follows the margin of a pumice clast.
