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

J.-A Hernandez (1, 2) , G. Morard (3, 4) , M. Guarguaglini (1) , R. Alonso‐mori (5) , A. Benuzzi‐mounaix (1) , R. Bolis (1) , G. Fiquet (3) , E. Galtier (5) , A. E Gleason (5) , S. Glenzer (5) , F. Guyot (3) , B. Ko (6) , H. J Lee (5) , W. L Mao (7) , B. Nagler (5) , N. Ozaki (8) , A. K Schuster (9) , S. H Shim (6) , T. Vinci (1) , A. Ravasio (1)

1 LULI - Laboratoire pour l'utilisation des lasers intenses
2 CEED - Centre for Earth Evolution and Dynamics [Oslo]
3 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie
4 ISTerre - Institut des Sciences de la Terre
5 SLAC - SLAC National Accelerator Laboratory
6 ASU - Arizona State University [Tempe]
7 Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University
8 Osaka University [Osaka]
9 HZDR - Helmholtz-Zentrum Dresden-Rossendorf

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.

Domaines: Géophysique [physics.geo-ph]

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, 2020, 47 (15), ⟨10.1029/2020GL088887⟩. ⟨hal-03006363⟩