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Figure F49. Photomicrographs of alteration of granoblastic material. A. Orthopyroxene replaced by amphibole and talc (Sample 335-1256D-238R-1, 2–4 cm; Thin Section 6) (plane-polarized light). B. Contact between granoblastic material (bottom) intruded and overgrown by coarser gabbroic material (top) (Sample 335-1256D-Run12-RCJB-Rock D; Thin Section 23) (plane-polarized light). Granoblastic material within 5–10 mm of the contact is more highly altered (pyroxenes replaced by amphibole) than the granoblastic host rock. C. Granoblastic “vein,” 1 mm wide, consisting of plagioclase, clinopyroxene, and orthopyroxene, along with sparse Fe-Ti oxides, cut by discontinuous brown amphibole vein (Sample 335-1256D-238R-1, 13–15 cm; Thin Section 7) (plane-polarized light). Host rock contains 5 mm wide amphibole-rich alteration halo, where pyroxenes are replace by amphibole.

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