| Text Description: |
Rubbly outcrop of a dike trending ~N84°E at Site 12. Fine grained, vesicular, hypocrystalline, seriate porphyritic with a matrix of cryptocrystalline material, opaque, orthopyroxene, pale brown glass and minor alteration. Plagioclase phenocrysts (An53) are up to 0.7 mm and both oscillatory and normal zoning are common. Amphibole phenocrysts are up to 0.8 mm and are dehydrated to granular opaque masses with green-brown pleochroic cores; most grains are entirely replaced. Orthopyroxene phenocrysts are up to 0.3 mm. Opaque phenocrysts are up to 0.2 mm (not including pseudomorphs after amphibole). Trachydacite. |