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Direct observation of shock-induced disordering of enstatite below the melting temperature

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 (XRD) to laser-driven shock-compression. Shock compression induces a disordering of the crystalline structure evidenced by the appearance of a diffuse XRD signal at nanosecond time scales 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.
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https://hal.archives-ouvertes.fr/hal-03086417
Contributor : Alessandra Benuzzi Mounaix <>
Submitted on : Tuesday, December 22, 2020 - 4:17:56 PM
Last modification on : Tuesday, March 2, 2021 - 11:14:06 AM

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J.-A Hernandez, G. Morard, M. Guarguaglini, R. Alonso‐mori, A. Benuzzi‐mounaix, et al.. Direct observation of shock-induced disordering of enstatite below the melting temperature. Geophysical Research Letters, American Geophysical Union, 2020, 47 (15), ⟨10.1029/2020GL088887⟩. ⟨hal-03086417⟩

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