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Figure F32. Thin section photomicrographs of altered olivine. A, B. Partially altered olivine. The rim is altered to iddingsite, with the inner portions comprising secondary smectite and minor chlorite or serpentine (lizardite) (conglomerate of Unit II, Sample 330-U1372A-7R-4, 135–138 cm; Thin Section 19): (A) plane-polarized light, (B) crossed polars. C. Olivine crystals completely altered to iddingsite in aphyric basalt (Unit VI, Sample 330-U1372A-11R-3, 83–85 cm; Thin Section 31; plane-polarized light). D. Olivine completely altered to green and brown (saponite) clay minerals and carbonates (sparsely olivine-phyric basalt of Unit V, Sample 330-U1372A-11R-1, 84–86 cm; Thin Section 29; crossed polars). E, F. Moderately to completely altered olivine from massive flow in Unit XVI (Sample 330-U1372A-31R-1, 61–63 cm; Thin Section 68; plane-polarized light), displaying (E) secondary brown clay minerals or green clay (nontronite), perhaps associated with a small amount of (F) serpentine (lizardite) (olivine-plagioclase-phyric basalt).

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