Figure F24. Photomicrographs showing a large plagioclase phenocryst with complex zonation (Sample 198-1213B-33R-6, 106-108 cm). One zone is preferentially altered to green clay minerals, along with minerals in surrounding groundmass. The upper view is in plane-polarized light, and the lower view is with nicols crossed.

Figure F24. Photomicrographs showing a large plagioclase phenocryst with complex zonation (Sample 198-1213B-33R-6, 106-108 cm). One zone is preferentially altered to green clay minerals, along with minerals in surrounding groundmass. The upper view is in plane-polarized light, and the lower view is with nicols crossed.