Figure F10. Basalt. A, B. Sample 345-U1415N-4R-1, 12–15 cm (Piece 3); plane-polarized light). (A) Basalt containing a few plagioclase phenocrysts hosted in a matrix with abundant plagioclase microlites. Groundmass decreases in size toward the altered areas in the top right indicating proximity to a chilled margin. (B) Moderate-strength flow orientation of plagioclase microlites. C. Olivine xenocryst in olivine-phyric basalt showing subgrains, which together with clumps of olivine crystals elsewhere in the sample suggests the olivine may be entrained from a partially crystallized magma chamber (Sample 345-U1415N-2R-1, 5–7 cm [Piece 1]; under crossed polars). D. Groundmass of moderately olivine-phyric basalt (Sample 345-U1415N-1R-1, 62–66 cm [Piece 12]; under crossed polars). Larger plagioclase crystals (>0.5 mm long) contain deformation twins (red arrow).
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