Figure F23. Photomicrographs of olivine and spinel phenocrysts in Unit IV, Hole U1349A. A. Olivine replaced by clays, hematite, and iron oxyhydroxides (Thin Section 209; Sample 324-U1349A-7R-3, 39–43 cm). B. Cluster of euhedral olivine crystals, now altered, and former cracks prominently outlined by secondary minerals, as in A. A large brown spinel lies between two of the olivine crystals (Thin Section 207; Sample 324-U1349A-7R-2, 29–33 cm). C. Cluster of spinel crystals within an altered olivine. Olivine is replaced by calcite that is dusted with hematite, but spinel is largely unaltered. Some reticulate alteration can be seen on the uppermost spinel (Thin Section 220; Sample 324-U1349A-10R-4, 85–89 cm). D. Usual altered olivine containing isolated (bright, euhedral) crystals of Cr spinel. Largest crystal has a round former melt inclusion within it (Thin Section 219; Sample 324-U1349A-10R-2, 10–12 cm). A and B are under transmitted light; C and D are under reflected light.
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