Shock Compressed Forsterite Overturns Prior "Mixed Phase" Theories
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
To provide a better understanding of the interior structure and dynamics of the Earth’s mantle, it is imperative to know the equation of state and phase diagrams of MgO-MgSiO3 thermodynamic systems. A more detailed understanding of partial melting and chemical stratification of the mantle is provided from extensive research focused on Mg2SiO4 at high pressures over a wide range of thermodynamic conditions. However, there is no stable compound of Mg2SiO4 in the Earth’s lower mantle. Thus, in order to get an equilibrium state of homogeneous forsterite, it must be decomposed into at least two compounds, periclase and bridgmanite. In-situ powder x-ray diffraction observations of forsterite crystal structure samples shocked to 44(3) and 73(5) GPa, done at the Dynamic Compression Sector (DCS) of the U.S. Department of Energy’s Advanced Photon Source (APS) show chemical segregation of forsterite does not occur on dynamic timescales, but the nonequilibrium states persist to 73(5) GPa, where the shock temperature is predicted to be ~2500 K.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- DOE Contract Number:
- AC52-07NA27344
- OSTI ID:
- 1544471
- Report Number(s):
- LLNL-TR-772015; 963847
- Country of Publication:
- United States
- Language:
- English
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