Origin of composite pyroxenes and crystal habit change of pyroxene microcrystals in the 2011 Shinmoedake eruption

Abstract

The purpose is to research composite pyroxenes in ejecta of Shinmoedake 2011 eruption and check whether pyroxene shapes correlate with eruption styles. The center of composite pyroxene was an Opx layer and the both sides were Aug adjoining parallel to (100). This could be explained by epitaxial growth of Aug on Opx. The particles with oscillatory zoning of Mg/Fe and Al imply their formation even in the magma chamber. The trend of crystal habit of pyroxenes differed with eruption styles.