Figure 6
SEM images of pure SiO2 (lechatelierite). (a) Lechatelierite coating with swirling flow marks on an outer surface of AH glass. Sharp lechatelierite spikes are shown at the upper yellow arrow. From level 445, sample E301, 405 cm depth. (b) Lechatelierite coating on an outer surface of AH glass with oriented flow marks at arrows. (c) Distinctive patterns produced during the cooling of lechatelierite. The lechatelierite is a transparent outer layer on the wall of an interior vesicle and covers the Ca-rich aluminosilicate glass matrix. (d) Manually constructed EDS-based phase map shows how the surface irregularity (purple) distorted the thin lechatelierite coating (light red) that flowed over and around it, distorting the textural ridges. (e) Distinctive lechatelierite pattern that appears orthogonally oriented relative to crack in vesicle wall of AH glass. The lechatelierite coating is only several microns thick and these distortions indicate that lechatelierite flowed around the pre-existing grain. Glass samples are from level 457, sample E313, 413 cm depth.
