Figure F34. Photomicrographs of altered olivine phenocrysts in Unit V, Hole U1349A. A. Low-magnification perspective of the clustering and abundance of olivine (~5% of the rock). Olivine is replaced by light-colored clay minerals or chlorite. Iron oxyhydroxides are still concentrated near olivine rims and along former fractures (Thin Section 261; Sample 324-U1349A-16R-6, 56–61 cm). B. Altered olivine phenocryst, ~2 mm in diameter, replaced by clear clays or chlorite and iron oxyhydroxide (Thin Section 248; Sample 324-U1349A-14R-5, 25–31 cm). C–E. Three olivine phenocrysts 0.5–1.5 mm in length replaced by a clear fibrous mineral with low first-order birefringence (lizardite?). Residues of cracks are now lined with more highly birefringent clay and residual iron oxyhydroxide or hematite is present in C and D. Cr spinel is present in all three olivine crystals and is prominent in D. The adjacent bright mineral in D is altered plagioclase (Thin Section 261; Sample 324-U1349A-16R-6, 10–12 cm). A and B are under transmitted light; C–E are under cross-polarized light.
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