| Text Description: |
A 3-5’ thick, vertical dike trending N32°E, with a chill margin against silicic material of Dome A at Site 2. Fine-grained, vesicular, holocrystalline, pilotaxitic, porphyritic to glomeroporphyritic with a matrix of cryptocrystalline material, opaque, feldspar and alteration lining vesicles. Plagioclase phenocrysts (An37 - An61) are 2.2 -0.1 mm, and some have sieve textured cores or intermediate zones, complex zoning with prussian blue extinction, resorption embayments and rounded rims. Orthopyroxene phenocrysts are 1.2-0.1 mm and some have clinopyroxene rims or opaque inclusions. Clinopyroxene phenocrysts are 1.5-0.1 mm. Amphibole phenocrysts are 2.4-0.1 mm and display green-brown pleochroism; some grains have black coronas. Opaque phenocrysts are up to 0.3 mm. |