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Curious kinetic behavior in silica polymorphs solves seifertite puzzle in shocked meteorite
Tomoaki Kubo1, Takumi Kato1, Yuji Higo2
1Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan.
Science Advances
|November 25, 2015
Summary
Seifertite, a silica polymorph, is found in meteorites at lower pressures than expected. Its formation kinetics suggest shock durations of at least 0.01 seconds and impactor sizes of 50-100m.
Area of Science:
- Planetary Science
- Mineral Physics
- Geochemistry
Background:
- Seifertite, a high-pressure silica polymorph, is observed in shocked meteorites.
- Its thermodynamic stability requires pressures >100 GPa, inconsistent with early solar system shock events.
Purpose of the Study:
- Investigate the formation of seifertite under realistic shock conditions.
- Determine the kinetic factors influencing seifertite stability.
- Constrain impactor characteristics based on seifertite presence.
Main Methods:
- In situ X-ray diffraction measurements at high pressure and temperature.
- Analysis of kinetic differences between seifertite and stishovite formation.
- Modeling of shock duration and impactor size.
Main Results:
- Seifertite metastably forms at pressures as low as ~11 GPa.
- Formation kinetics are time-sensitive but temperature-insensitive.
- Presence of seifertite indicates shock durations >= 0.01 s and impactor sizes of 50-100 m.
Conclusions:
- Seifertite's metastable formation explains its presence in meteorites.
- Kinetic constraints provide insights into early solar system impact events.
- This finding refines our understanding of shock metamorphism in planetary bodies.
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