Figure 8
Melted chromite grains. (a) Two possible chrome-magnetite grains (Fe2+(Fe3+,Cr)2O4), one ~10 µm long and the other ~7.5 µm long, that melted and flowed together on the inner wall of AH glass vesicle. (b) Manually constructed EDS-based phase map of SEM image in (a) with chrome-magnetite in blue and AH glass matrix in light red. Field of view also contains melted titano-magnetite grain (green; equilibrium melting point: 1625 °C) and post-depositional, unmelted calcium silicate in purple. Note melted droplet of AH glass fused to the top of melted chrome-magnetite at upper right, indicating the melted chrome-magnetite was deposited while the AH glass was molten. (c) Irregular chrome-magnetite grain inside AH glass vesicle shows evidence that it melted and flowed as the glass cooled. Chromium is mixed with gold. All grains from level 449, sample E305, 412 cm depth.
