Figure F21. Photomicrographs of pseudomorphed olivine microphenocrysts. Olivine microphenocrysts in each are completely replaced by calcite, which perfectly pseudomorphs the crystal outlines and fractures and encloses (C) round altered glass inclusions and (A, B, D) unaltered Cr spinel. The euhedral morphologies in these samples are easy to see because the matrix of each sample is either very fine grained or spherulitic and crystallized near a pillow margin. These olivines were all present upon eruption. Calcite in B was subsequently stained by finely disseminated Fe oxyhydroxides. (A) Thin Section 59 (Sample 324-U1346A-16R-2, 30–31 cm); (B) Thin Section 52 (Sample 324-U1346A-14R-2, 97–98 cm); (C) Thin Section 61 (Sample 324-U1346A-16R-2, 85–88 cm); (D) Thin Section 46 (Sample 324-U1346A-13R-1, 85–88 cm). Transmitted light.
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