Figure 11: High resolution SEM mapping of the glass-palagonite interface and associated etch-tunnel zone (as observed on the freshly fractured surface of a basaltic glass “chip sample” of DSDP-418A-75-3[120–123]). (a, b, d, and e) Secondary electron images. (a) Overview of a representative region of the glass-palagonite interface, highlighting four microtextural domains (boundaries shown as yellow lines; also see (c)) that include two large FTETs and several hundred smaller ARTETs. (b) Close-up from (a) highlighting where the palagonite zone is encroaching upon (overprinting) the etch-tunnel zone. (c) Alteration map, showing the distribution of the four microtextural domains outlined in (a). (d) Close-up (from (a)) of the etch-tunnel zone, highlighting one FTET and several ARTETs. Note the similarity in size between the hypothetical fission track (green bar) and the FTET and between the hypothetical ARTs (pink dots) and the ARTETs. (e) Representative close-up (from (a)) of the palagonite zone. ARTs: alpha-recoil tracks; ARTETs: alpha-recoil track etch-tunnels; ETZ: etch-tunnel zone; FG: fresh basaltic glass; FT: fission track; FTET: fission track etch-tunnel; HT: hypothetical preexisting alpha-recoil track etch-tunnel; IZ: intermediate zone (between the ETZ and the PZ); P: palagonite; PZ: palagonite zone.