Silica polymorphs in Yamato-75011 Eucrite

Abstract

We studied silica polymorphs in Y-75011 eucrite and discuss their formation conditions. There are 2 types of silica polymorphs in basaltic clast, aggregate of quartz and cristobalite and single quartz. Aggregates were formed either by hydrothermal activity or crystallization from Si-rich magma with water or Na. Single quartz is likely to have crystallized from Si-rich melt. If water was involved in the formation of this basaltic clast, it suggests a wide occurrence of water in the Vesta crust.