Occurrence of quench olivine crystals in a basaltic dyke from Schirmacher Oasis, Queen Maud Land, East Antarctica

Presence of several morphologies of quench olivine crystals, which provide important clues on cooling rate(s) of magma, are reported here in a basaltic dyke, from the Precambrian gneissic terrain of Schirmacher Oasis, Queen Maud Land, East Antarctica. The dyke, composed of plagioclase, clinopyroxene, olivine, magnetite and glass, shows intergranular texture. It is alkali basalt in composition with low silica (SiO2 = 46.20-47.20) and negative Nb anomaly. The morphologies of quench olivine crystals suggest rapid cooling of the basaltic magma approximately at 15-80degreesC/hour. Further, the delicate nature of these quench olivine crystals, confined mostly to the glassy margins of the dyke, also suggest in situ crystallisation.