The breakdown of diopside to Ca-rich majorite and glass in a shocked H chondrite

Fine-grained assemblages of majorite and glassy grains are for the first time identified in a shock-induced melt vein in an H chondritic meteorite. The bulk chemical composition of these aggregates is similar to that of diopside CaMgSi2O6 in the host rock. Both majorite and glassy grains are Ca-rich and their formulae can be approximated as (Mg0.65Fe0.09Ca0.26)SiO3 and (Mg0.23Fe0.05Ca0.72)SiO3, respectively. These Ca-rich assemblages are dissociation products of the host diopside and were produced at ∼18–24 GPa by a shock event. The CaSiO3-rich glass is inferred to have crystallized in a perovskite structure, but was vitrified during the pressure release.