Figure F305. Alteration patches in sheeted dikes. A. Elongate alteration patches (interval 312-1256D-187R-1, 47–55 cm). B. Alteration patch (Thin Section 33; Sample 312-1256D-194R-1, 8–13 cm) (cross-polarized light; field of view [FOV] = 2.25 mm). C. Inclined band of alteration patches (Thin Section 4; Sample 312-1256D-174R-1, 70–73 cm). D. Alteration patch (Thin Section 4; Sample 312-1256D-174R-1, 70–73 cm) (cross-polarized light; FOV = 4.5 mm). E. Vein cutting (coeval with?) alteration patches (interval 312-1256D-176R-1, 6–19 cm). F. Vein and vein-related alteration within an alteration patch (Thin Section 10; Sample 312-1256D-176R-1, 8–12 cm) (plane-polarized light; FOV = 2.25). G. Close-up sketch of E, showing detailed vein relationships within alteration patch.
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