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Hydrous SiO2 in subducted oceanic crust and H2O transport to the core-mantle boundary.
- Source :
-
Earth & Planetary Science Letters . Sep2022, Vol. 594, pN.PAG-N.PAG. 1p. - Publication Year :
- 2022
-
Abstract
- Subduction of oceanic lithosphere transports surface H 2 O into the mantle. Recent studies show that dense SiO 2 in the form of stishovite, an abundant mineral in subducted oceanic crust at depths greater than ∼270 km, has the potential to host and transport a considerable amount of H 2 O into the lower mantle, but the H 2 O storage capacity of SiO 2 phases at high pressure and temperature remains uncertain. We investigate the hydration of stishovite and its higher-pressure polymorphs, β -stishovite and seifertite, with in situ X-ray diffraction experiments at high pressures and temperatures. The H 2 O contents in SiO 2 phases are quantified based on observed increases in unit cell volume relative to the anhydrous SiO 2 system. Density functional theory (DFT) computations permit calibration of water content as a function of volume change based on interstitial substitution of H 2 O. Regression of our experimental data indicates an H 2 O storage capacity in stishovite of ∼3.5 wt% in the transition zone and shallow lower mantle, decreasing to about 0.8 wt% at the base of the mantle. We find that SiO 2 -bearing subducted oceanic crust can accommodate all the H 2 O in slab lithosphere that survives sub-arc dehydration. Hydration of silica phases in subducted oceanic crust and their unparalleled capacity to host significant amounts of H 2 O even at high mantle temperatures provides a unique mechanism for transport and storage of water in the deepest mantle. • Quantification of the H 2 O storage capacity in hydrous silica in the deep mantle. • Parameterization of the H 2 O storage capacity in hydrous silica as a function of P-T. • Interstitial substitution of H 2 O dominates incorporation water of hydrous silica. • Hydrous silica plays an important role in transporting water to the deep Earth. [ABSTRACT FROM AUTHOR]
- Subjects :
- *OCEANIC crust
*CORE-mantle boundary
*HYDROUS
*LITHOSPHERE
*WATER storage
Subjects
Details
- Language :
- English
- ISSN :
- 0012821X
- Volume :
- 594
- Database :
- Academic Search Index
- Journal :
- Earth & Planetary Science Letters
- Publication Type :
- Academic Journal
- Accession number :
- 158513117
- Full Text :
- https://doi.org/10.1016/j.epsl.2022.117708