Figure F22. Photomicrographs of variations in crystal morphology and grain size across a highly vesiculated basalt in Subunit IVa, Hole U1349A (Thin Section 209; Sample 324-U1349A-7R-3, 78–81 cm). A. Coalesced circular spherulites ~50 µm in diameter are strongly oxidized to reddish brown and lie between large vesicles lined with clays and filled with calcite. Tiny plagioclase microlites are in the material. B. Zone of intersecting sheaf spherulites altered to brown clays, with irregular bundles and individual crystals of plagioclase. The vesicles are filled with calcite. C. Zone of radiating acicular plagioclases having larger bundles of intergrown plagioclase and altered clinopyroxene (yellow) with dendritic overgrowths. D. Coarsest grained part of the thin section, in which plagioclase-clinopyroxene intergrowths are starting to crystallize into networks. An altered clinopyroxene microphenocryst is at the lower right, and a large pair of altered olivine crystals, both replaced by clays and iron oxyhydroxides, is on the left. Small crystals of Cr spinel can be seen near and in the olivine.
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