Figure F112. Close-up photographs of mixed halos. A. A network of 0.1- to 2-mm-wide veins, composed of saponite and iron oxyhydroxides, with 10- to 15-mm-wide mixed alteration halos (interval 206-1256D-18R-2, 12-27 cm). A 30-mm-wide black alteration halo overprints the background dark gray alteration of the basalt at 24-27 cm; the vein associated with this halo is not preserved. B. A 1-mm-wide saponite vein with mixed alteration halo up to 15 mm wide. Where smaller veins or brittle fractures intersect the main vein, the alteration halo widens, extending a few millimeters along the small veins (interval 206-1256D-26R-6, 13-26 cm). C. A 2-mm-wide celadonite, saponite, and iron oxyhydroxide vein with an impressive 5- to 15-mm-wide mixed alteration halo. The dark zone of the mixed halo is blue green and is particularly celadonite rich (interval 206-1256D-61R-1, 50-59 cm). D. A network of saponite and silica veins, with a few percent iron oxyhydroxide, pyrite, and calcium carbonate, is flanked by a 25-mm-wide mixed halo with a coarse (up to 1 mm wide) pyrite front (interval 206-1256D-59R-1, 0-40 cm).

Figure F112. Close-up photographs of mixed halos. A. A network of 0.1- to 2-mm-wide veins, composed of saponite and iron oxyhydroxides, with 10- to 15-mm-wide mixed alteration halos (interval 206-1256D-18R-2, 12-27 cm). A 30-mm-wide black alteration halo overprints the background dark gray alteration of the basalt at 24-27 cm; the vein associated with this halo is not preserved. B. A 1-mm-wide saponite vein with mixed alteration halo up to 15 mm wide. Where smaller veins or brittle fractures intersect the main vein, the alteration halo widens, extending a few millimeters along the small veins (interval 206-1256D-26R-6, 13-26 cm). C. A 2-mm-wide celadonite, saponite, and iron oxyhydroxide vein with an impressive 5- to 15-mm-wide mixed alteration halo. The dark zone of the mixed halo is blue green and is particularly celadonite rich (interval 206-1256D-61R-1, 50-59 cm). D. A network of saponite and silica veins, with a few percent iron oxyhydroxide, pyrite, and calcium carbonate, is flanked by a 25-mm-wide mixed halo with a coarse (up to 1 mm wide) pyrite front (interval 206-1256D-59R-1, 0-40 cm).