Figure F26. Photograph of interval 187-1157B-3R-1, 137-147 cm, showing calcite veins dissecting basalt. The veins are surrounded by symmetric alteration halos in which groundmass is mostly replaced by smectite, and Fe oxyhydroxide and olivine phenocrysts are iddingsitized. Note the irregular vein/wall-rock boundary. Spotty Mn oxide is common within the calcite veins.