Fig. 3

Resultant microstructures. a–c Under plane-polarized light. a A pair of patchy pseudotachylytes (Pt) developed during slip strengthening. Note that the pseudotachylytes are mantled by the altered chert (Ac). b Pseudotachylyte (Pt) and altered chert (Ac) formed during the late stage of slip strengthening. c Pseudotachylyte boundary showing an embayed margin. Location of the figure is shown in (a). d Optically isotropic matrices of pseudotachylyte (Pt) and altered chert (Ac) under cross-polarized light. Note that the quartz veins are cut by pseudotachylyte but preserved in the altered chert (Ac). Location of the figure is shown in (b). e–i Under back-scattered electron (BSE) images. e Appearance of experimentally generated pseudotachylyte showing a fragment-laden, glass-supported texture. f A fragment in the pseudotachylyte matrix showing an embayed margin. g Cracks surrounding a fragment in the pseudotachylyte matrix. h A radiolarian fossil (Rf) in the matrix of the altered chert (Ac). i The presence of vesicles in the matrix of the altered chert. Location of the figure is shown in (h). Qz, quartz. j Energy-dispersive X-ray spectroscopy (EDS) spectrum of the matrix of the altered chert. Location of the measured point is shown in (i)