| Text Description: |
A 7’ thick vertical dike trending N10°W with good columnar jointing and a 8” thick bake zone where it is in contact with silicic material from Dome A at Site 3. Fine grained, vesicular, hypocrystalline, porphyritic to glomeroporphyritic with a matrix of brown glass, mesostasis, opaque, plagioclase and minor altered patches. Plagioclase phenocrysts (An55) are up to 2.75 mm and commonly have oscillatory zoning, some grains have resorption embayments and are frequently riddled with melt inclusions, and pyroxene or opaque inclusions. Orthopyroxene phenocrysts are up to 2.75 mm, intensely pleochroic, and often contain opaque inclusions and occasionally have clinopyroxene rims. Clinopyroxene phenocrysts are up to 1.1 mm and occasionally have orthopyroxene cores. Opaque phenocrysts are up to 0.4 mm. |