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Figure F287. Olivine alteration in gabbros. A. Olivine partially replaced by pleochroic (brown to green) phyllosilicate (unidentified) + magnetite + minor talc (Thin Section 90; Sample 312-1256D-223R-1, 42–43 cm; 1449.72 mbsf) (plane-polarized light; field of view [FOV] = 2.25 mm). An outer zone of alteration is composed of chlorite and actinolite. B. Same as A; cross-polarized light. C. Detail of A, showing magnetite + talc (left) and the pleochroic phyllosilicate (center) and fresh olivine (right) (plane-polarized light; FOV = 0.6 mm). D. Same as C; cross-polarized light. E. Olivine completely replaced (bottom) by dark green (unidentified) phyllosilicate + magnetite with a chlorite-actinolite reaction rim (center) between the olivine and plagioclase (top) (Thin Section 79; Sample 312-1256D-217R-1, 64–69 cm; 1422.24 mbsf) (plane-polarized light, FOV = 0.6 mm). F. Same as E; cross-polarized light.

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