Curious kinetic behavior in silica polymorphs solves seifertite puzzle in shocked meteorite

摘要: The presence of seifertite, one the high-pressure polymorphs silica, in achondritic shocked meteorites has been problematic because this phase is thermodynamically stable at more than ~100 GPa, unrealistically conditions for shock events early solar system. We conducted situ x-ray diffraction measurements high pressure and temperatures, found that it metastably appears down to ~11 GPa owing clear difference kinetics between metastable seifertite stishovite formations. temperature-insensitive but time-sensitive formation uniquely constrains critical duration size impactor on differentiated parental bodies are least ~0.01 s ~50 100 m, respectively, from seifertite.