High-pressure behavior of hydrous phases
Abstract
One of the most distinguishing features of the Earth is its surface water, which is a crucial component in making it a habitable planet. How this water is partitioned among the various reservoirs within the Earth's interior is of considerable interest to the Solid Earth Sciences community. In convergent plate margins such as subduction zone, the hydrous phases in the subducting slabs deliver water into the Earth's interior. Upon reaching greater depths, depending on the limits of their thermodynamic stability, the hydrous phases dehydrate, releasing water. A fraction of water is released back into the hydrosphere through arc volcanism. Recent estimates show that the worldwide flux of water from subducting slabs amounts to about one ocean mass over the age of the Earth. The water in the Earth's interior is stored in several distinct forms: as aqueous fluids; hydrous silicate melts; nominally anhydrous phases; grain boundaries, and various hydrous phases. Among these multiple hosts, hydrous phases are particularly important because they influence solid earth processes in the crust and mantle. The thermodynamic stability of hydrous phases dictates how efficiently they transport and store water in the Earth's interior. Their presence severely affects the onset of melting. Hydrous phases that are likely to be stable at higher pressures are often not recorded in natural samples. It is possible that these hydrous phases are not sampled by melts that arise from depths that are shallower than where high-pressure hydrous phases may occur. It is also possible that these hydrous phases do not survive exhumation. In addition, many hydrous phases might have limited thermal stability. High-pressure experiments and first-principles simulations based on density functional theory (DFT) have been crucial in enhancing our understanding of hydrous phases that are likely to be present in the Earth's mantle and subduction zones. In this study, we present DFT results and compare them with experimental studies. In particular, we provide constraints on the crystal structure, thermodynamic stability, equation of state, elasticity of hydrous phases, and the degree of mantle hydration. Acknowledgements: MM is supported by NSF EAR 1639552, 1634422.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMMR12A..08M
- Keywords:
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- 3909 Elasticity and anelasticity;
- MINERAL PHYSICSDE: 3954 X-ray;
- neutron;
- and electron spectroscopy and diffraction;
- MINERAL PHYSICSDE: 3620 Mineral and crystal chemistry;
- MINERALOGY AND PETROLOGYDE: 3694 Instruments and techniques;
- MINERALOGY AND PETROLOGY