MORPHOLOGY AND CHEMICAL COMPOSITION OF ORTHOPYROXENES IN THE MELT IMPACTITES OF THE BOLTYSH ASTROBLEME

Abstract

The melt impactites (tagamites) of the Boltysh astrobleme (in the Ukraine) form a body more than 200 m thick (the diameter of the structure is approximately 24 km). The rocks of the target area consist of Precabrian granites and granitegneisses. The good preservation of the body of melt impactites and the fresh appearance and only slight devitrification of the rocks have led investigators to a detailed study of the chemical composition of these rocks and their minerals with the aim of deepening understanding of the processes in the formation of impact melts and the history of their subsequent solidification. This article considers in detail the morphology and chemical features of the orthopyroxenes of incompletely crystallized melt impactites. Pyroxene crystallized along with plagioclase during the cooling of the impact melts of the Boltysh meteorite crator. This study was accomplished with the aid of scanning electron microscopy (SEM) and microprobe analysis (MPA).