Stability field of δ-AlOOH investigated with ab-initio calculations
Abstract
As a potential terrestrial water carrier from upper mantle to lower mantle, δ-AlOOH is a well-known hydrous phase in subducting slabs that serves as an essential component in both phase H and phase Egg under high temperature and high pressure. To understand the mechanisms of water transportation in the mantle and the way in which Earth evolves, we need to determine the dehydration boundaries of this mineral [1]. Previous theoretical studies have focused only on the low-pressure static behavior of δ-AlOOH in the upper mantle and transition zone, leaving high-temperature high-pressure properties and dehydration boundaries undiscovered. Experimental investigations have shown that stability pressure range of δ-AlOOH covers the entire Earth's mantle and could remain as a stable phase in colder slabs down to the core-mantle boundary [2].
In this study, we present an ab initio investigation of the structural, dynamic, and thermodynamic stability of δ-AlOOH to multi-Mbar pressures. We are particularly interested in assessing the dehydration boundary up to pressures exceeding those of the Earth's mantle as well as the possibility of alternative polymorphs at pressures relevant to terrestrial exoplanets. [1] Thompson, A. B. Water in the Earth's upper mantle. Nature 358, 295-302 (1992). [2] Duan, Y. et al. Phase stability and thermal equation of state of δ-AlOOH: Implication for water transportation to the Deep Lower Mantle. Earth Planet. Sci. Lett. 494, 92-98 (2018).- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMMR23B0100L
- Keywords:
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- 1038 Mantle processes;
- GEOCHEMISTRYDE: 3924 High-pressure behavior;
- MINERAL PHYSICSDE: 3630 Experimental mineralogy and petrology;
- MINERALOGY AND PETROLOGYDE: 5199 General or miscellaneous;
- PHYSICAL PROPERTIES OF ROCKS