Figure 13: High resolution SEM (secondary electron) imaging of fission track etch-tunnels (FTETs) at the glass-palagonite interface (as observed on the freshly fractured surfaces of basaltic glass “chip samples” of DSDP-418A-75-3[120–123]). (a–d) Images of four FTETs shown at the same scale, all of which contain authigenic platy smectite. Note how two of these FTETs ((a) and (d)) are interconnected to several smaller ARTETs as a part of the same porosity/etch-tunnel network. In addition, all four FTETs exhibit two contrasting types of glass-dissolution interface: (1) a smooth interface (labelled “SI”) at regions distal to secondary smectite growth and (2) a “cusp and caries” textured interface (labelled “CCT”) at regions undergoing dissolution in the vicinity of secondary smectite growth (see Figure 14 for further explanation of CCT). (e) Close-up from (b), highlighting authigenic platy smectite within an FTET, as well as well-developed cusp and caries microtexture. (f) Interpretation of the four large etch-tunnels shown in (a–d) as variably oriented cross sections through FTETs of essentially the same shape and size (i.e., peanut-shaped and ~8 μm long). ARTETs: alpha-recoil track etch-tunnels; CCT: “cusp and caries” texture; FTET: fission track etch-tunnel; SI: smooth interface; Sm: platy smectite.