| Text Description: |
Gray outcrop sticking up through the talus of Dome A at Site 2. There is obvious magma mixing with very large amphibole crystals and white blobs of material with black glassy rims. Fine grained, holocrystalline, trachytic, porphyritic to seriate porphyritic with a matrix of mesostasis, plagioclase, opaque and alteration. Plagioclase phenocrysts (An 31-An63) are up to 2.5 mm, commonly display sieve textured zones, resorbed edges or less commonly resorption embayments, overgrowth rims, and complex zoning. Orthopyroxene phenocrysts are up to 2.25 mm. Clinopyroxene phenocrysts are up to 0.45 mm. Amphibole phenocrysts are up to 0.5 mm and have thick brownish rims that are replacing the crystal. Mode: 83.0% matrix, 13.5% plagioclase, 0.4% clinopyroxene, 1.7% orthopyroxene, 1.1% alteration, 0.3% vesicles. |