| Text Description: |
A vertical dike trending S65°E that intruded into the brecciated unit (sBA9) at Site 12. There is a 10 cm chill margin that is very glassy. Fine grained, vesicular, hypocrystalline, seriate porphyritic with a matrix of plagioclase, opaque, pale brown glass, microlites and orthopyroxene?. Plagioclase phenocrysts (An39 - An52) are up to 1.7 mm and both normal and oscillatory zoning are common; the largest grains often have thin overgrowth rims. Amphibole phenocrysts are up to 0.8 mm, and dehydrated to granular opaque masses with green-brown pleochroic cores; most grains are entirely replaced. Orthopyroxene phenocrysts are up to 0.25 mm. Opaque phenocrysts are up to 0.5 mm (primary not pseudomorphs after amphibole). 83.7% matrix, 10.1% plagioclase, 0.3% opaque, 0.1% altered phase, 0.1% alteration, 5.7% vesicles. Trachydacite. |