| Text Description: |
Outcrop of rubbly plates and blocks at Gutbuster. Fine grained, vesicular, holocrystalline, seriate to glomeroporphyritic with a matrix of mesostasis, opaque, plagioclase and orthopyroxene?. Cognate inclusions of plagioclase (An41, An55), orthopyroxene with clinopyroxene rims, opaque and clinopyroxene are present. Plagioclase phenocrysts (An38 - An58) are up to 2.0 mm and some have sieve textured zones; there are resorbed grains with overgrowth rims; oscillatory zoning is common and normal zoning is common in smaller grains. Olivine phenocrysts are up to 1.25 mm and occasionally are rimmed with small orthopyroxene crystals. Orthopyroxene phenocrysts are up to 2.2 mm and clinopyroxene rims are common. Clinopyroxene phenocrysts are up to 1.25 mm. Opaque phenocrysts are up to 0.1 mm. 76.6% matrix, 16.3% plagioclase, 2.1% olivine, 1.5% clinopyroxene, 3.0% orthopyroxene, 0.5% vesicles. |