Figure F32. Photomicrographs of textural variation from rim to interior of an altered hyaloclastite breccia fragment in Unit V, Hole U1349A (Thin Section 258; Sample 324-U1349A-16R-2, 7–14 cm). A–D. Increasing crystallinity from the altered glass rim (with chloritized edge) in A to zones of acicular plagioclase microlites in B and C, and finally incipient development of plagioclase-clinopyroxene network structure set in a darker and finer grained matrix in D. Olivine phenocrysts present in A–C are altered to brown clays with green chloritic rims but retain small crystals of Cr spinel. E. Remnants of three hopper olivine crystals set in a matrix with more and less crystalline portions, as in D. F. One of a number of unusual button-shaped objects, consisting of bundles or sheafs of a fine needle-like mineral with intermediate birefringence. These may be incipient clinopyroxene rosettes that are now altered to clay minerals. Transmitted light.
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