| Text Description: |
From a 20-25' thick flow at the top of the second andesite package at Site 1 in the Boyden Hills. Fine-grained, vesicular, diktytaxitic, hypocrystalline, intersertal, intergranular, seriate porphyritic with a matrix of brown glass, mesostasis, opaque (sometimes with dendritic habit), and plagioclase microlites. Plagioclase phenocrysts (An38-An61) are up to 2.63 mm, frequently have normal zoning, and occasionally have sieve or spongy textured zones, or olivine inclusions. Olivine phenocrysts are up to 2.0 mm, and smaller grains tend to occur in clots; occasionally have opaque inclusions. Clinopyroxene phenocrysts are up to 0.65 mm. Opaque phenocrysts are up to 0.1 mm, but most opaque grains are of matrix size. Mode: 27% matrix, 48.7% plagioclase, 9.1% olivine, 10.5% clinopyroxene, 4.7% vesicles. |