High-pressure behavior of 10 Å phase (Mg3Si4O10(OH)2.H2O)
Abstract
Layered hydrous phases such as serpentine (Mg3Si2O5(OH)4), talc (Mg3Si4O10(OH)2), chlorite (Mg5Al(Si3Al)O10(OH)8), and 10 Å phase (Mg3Si4O10(OH)2.xH2O, where x=1,2) play important roles in transporting water into the Earth's interior. Using first principles simulations, we investigate the high-pressure behavior of 10 Å phase. In particular, we investigate the crystal structure of 10 Å phase and how it evolves upon compression. The predicted lattice parameters from the first principles simulations are in good agreement with the previous x-ray diffraction studies. The energy vs. volume results can be expressed in terms of a Birch-Murnaghan finite strain fit, with parameters, V0, K0 and K0' being 525.7 Å3, 32.1 GPa, and 17.4 respectively. The predicted V0 is greater than that of the experimentally determined value by 5.4 %. This discrepancy is often typical for the density functional theory calculations based on Genaralized Gradient Approximations (GGA). We are exploring the elasticity of 10 Å phase and how it varies as a function of pressure. The layered hydrous silicates such as serpentine, chlorite, and talc are often assicated with significant elastic anisotropy and are often responsible for the large delay times observed in certain subduction zones. We will accurately constrain the sound wave velocity and elastic anisotropy of 10 Å phase to gain insight into the degree of shallow mantle hydration and explain geophysical observations pertaining to subduction zones. Acknowledgements: The research is supported by NSF EAR 1639552, 1634422.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMDI31B2628M
- Keywords:
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- 1031 Subduction zone processes;
- GEOCHEMISTRYDE: 3999 General or miscellaneous;
- MINERAL PHYSICSDE: 7240 Subduction zones;
- SEISMOLOGYDE: 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICS