Occurrence of Quench Plagioclase and Pyroxene Crystals in Sitagota Mafic Volcanics of Dongargarh Supergroup, Central India

Sitagota mafic volcanics, belonging to the Khairagarh Group of Dongargarh Supergroup, are composed of numerous basaltic flows. One of these basaltic flow is characterized by the occurrence of several morphologies of quench crystals of pyroxene and plagioclase. Plagioclase shows a spherulitic pattern, while pyroxene shows elongate parallel chain, dendritic and spherulitic habits. Most of these crystals are similar to those reported from submarme basalts, lunar basalts, spinifex textured rocks and experimentally produced quench textures. The occurrence of quench crystals, in this basaltic flow suggests that these forms were produced by rapid cooling rates of the basaltic magma, approximately at 2-50°C/hr. Further, the delicate nature of these quench plagioclase and pyroxene crystals, which are confined to the upper part of the flow, suggests in situ crystallization.