Figure 8: Petrographic and SEM study of white (K-Al-Si)-rich devitrified zones (in thin section). (a–f) Photomicrographs in plane polarized light, highlighting development of “lip-shaped” (K-Al-Si)-rich devitrified zones along late (f2) fractures (a–c), as well as halos around some plagioclase crystals (d–f). (a, b): sample DSDP-418A-75-3[120–123]; (d, e): sample DSDP-418A-68-3[40–43]; (c, f): sample DSDP-418A-72-4[13–15]. (g–i) SEM (BSE) images of a polished thin section of sample DSDP-418A-68-3[40–43], highlighting white (K-Al-Si)-rich devitrified zones. Note: palagonitization of basaltic glass along early (f1) fractures (a, d, g, and h) and the stepwise/punctuated “cracking” of basaltic glass (from through in (g, h) and from f1 through f2 in (a, d, g, and h)), inferred based on the pattern of termination of successively younger fractures against older ones. (j) SEM EDS spectra for white (K-Al-Si)-rich devitrified zones (see petrographic context in (a, i)), showing abundant Si, Al, and K—consistent with microcrystalline K-feldspar ± quartz or cristobalite. cf: corrosion front; D: white (K-Al-Si)-rich devitrified zones; f1 (including ): early fractures along which palagonite is rooted; f2: late fractures along which white (K-Al-Si)-rich devitrified zones are rooted; FG: fresh basaltic glass; GP: granular palagonite ART alteration; gt: minor granular corrosion texture associated with devitrified zones; H: halos of white (K-Al-Si)-rich devitrified zones around plagioclase; ip: initial palagonite; P: palagonite; plg: plagioclase.