Direct Observation of Shock-Induced Disordering of Enstatite Below the Melting Temperature

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Date
2020
Volume
47
Issue
15
Journal
Geophysical Research Letters
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Publisher
Hoboken, NJ [u.a.] : Wiley
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Abstract

We report in situ structural measurements of shock-compressed single crystal orthoenstatite up to 337 ± 55 GPa on the Hugoniot, obtained by coupling ultrafast X-ray diffraction to laser-driven shock compression. Shock compression induces a disordering of the crystalline structure evidenced by the appearance of a diffuse X-ray diffraction signal at nanosecond timescales at 80 ± 13 GPa on the Hugoniot, well below the equilibrium melting pressure (>170 GPa). The formation of bridgmanite and post-perovskite have been indirectly reported in microsecond-scale plate-impact experiments. Therefore, we interpret the high-pressure disordered state we observed at nanosecond scale as an intermediate structure from which bridgmanite and post-perovskite crystallize at longer timescales. This evidence of a disordered structure of MgSiO3 on the Hugoniot indicates that the degree of polymerization of silicates is a key parameter to constrain the actual thermodynamics of shocks in natural environments. © 2020. The Authors.

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Hernandez, J.-A., Morard, G., Guarguaglini, M., Alonso-Mori, R., Benuzzi-Mounaix, A., Bolis, R., et al. (2020). Direct Observation of Shock-Induced Disordering of Enstatite Below the Melting Temperature (Hoboken, NJ [u.a.] : Wiley). Hoboken, NJ [u.a.] : Wiley. https://doi.org//10.1029/2020GL088887
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CC BY 4.0 Unported