Discussion
The variety of picrific basalt having abundant olivine (20-50 volume %) and less frequent augite phenocrysts with the groundmass of augite, olivine and plagioclase is called :
Answer: A
This variety is oceanite.
Oceanite is a picritic basalt crowded with olivine phenocrysts (roughly 20 to 50 per cent of the rock) and fewer augite phenocrysts, in a groundmass of augite, olivine and plagioclase. It is typical of oceanic island volcanoes such as Reunion and Hawaii, where olivine accumulates in the magma.
Ankaramite is the opposite picritic variety, with abundant augite phenocrysts and less olivine. Diabase (dolerite) is an ordinary medium-grained basaltic rock, and kimberlite is a volatile-rich ultramafic rock known for diamonds.
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