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Published December 2025 | Version Supplemental material
Journal Article Open

Sound velocities of (Al,Fe)-phase H and the seismic visibility of dense oxyhydroxides in Earth's lower mantle

Creators

  • 1. ROR icon California Institute of Technology
  • 2. ROR icon University of Bayreuth
  • 3. ROR icon Okayama University
  • 4. ROR icon Gakushuin University
  • 5. ROR icon Lawrence Livermore National Laboratory
  • 6. ROR icon Argonne National Laboratory

Abstract

Oxyhydroxide phases in the (Al,Fe)OOH–MgSiO2(OH)2 system may form within oceanic lithosphere and transport hydrogen in their crystal structures into the lowermost mantle via cold, subducted slabs. In this work, we present new measurements of the seismic wavespeeds of the dense oxyhydroxide (Al,Fe)-phase H (Al0.84Fe³⁺0.0₇Mg0.02Si0.06OOH) to 100 GPa constrained by nuclear resonant inelastic X-ray scattering, incorporating previous constraints on the equation of state of this phase. At 300 K and pressure greater than 70 GPa, (Al,Fe)-phase H exhibits high P-wave speeds (δlnV_P >+12%) and low S-wave speeds (δlnV_S <−7%) relative to the preliminary reference Earth model (PREM). Experimentally determined sound velocities are incorporated into a model of a hydrous metabasalt including (Al,Fe)-phase H and compared with the seismic wavespeeds of pyrolitic mantle along appropriate adiabats. Hydrous metabasalt may reproduce an anti-correlation of negative shear wave velocity and positive bulk sound velocity at the upper edges of large, low velocity provinces when compared to pyrolitic mantle but has similar wavespeeds to PREM in this region. Hydrous metabasalt with conceivable concentrations of (Al,Fe)-phase H can be distinguished from PREM in V_S at mid-mantle depths (1100–1700 km) and in V_P at shallower depths (750–1000 km). Subducted hydrous metabasalt could contribute to scattering of seismic waves across the depth interval of the post-stishovite transition, which may be affected by the formation of (Al,Fe)-phase H.

Copyright and License

© 2025 Published by Elsevier B.V.

Acknowledgement

The authors would like to thank Cijin Zhou (Caltech) and Barbara Lavina (Advanced Photon Source) for help during NRIXS experiments at Argonne National Laboratory and additional discussion. Additional thanks to two anonymous reviewers, whose reviews and comments improved the manuscript.

Funding

This work was supported by the National Science Foundation’s (NSF) Collaborative Studies of the Earth’s Deep Interior (CSEDI) under EAR-2303148. Portions of this work were performed at sectors 3 and 13-GeoSoilEnviroCARS of the Advanced Photon Source (APS), a United States Department of Energy (DOE) facility. Use of the APS is supported by the U.S. DOE Office of Science (DE-AC02- 06CH11357). Sector 3 operations were partially supported by COMPRES (EAR-1661511). GeoSoilEnviroCARS is supported by NSF – Earth Sciences (EAR-1634415) and DOE-Geosciences (DE-FG02-94ER14466). T.I. is supported by the Japan society for the Promotion of Science (JSPS) KAKENHI grants 23K19067 and 24K00735.

Data Availability

Results of nuclear resonant inelastic X-ray scattering experiments can be obtained from the Caltech DATA repository: doi: 10.22002/8v9yv-9mm73(Strozewski et al., 2024). Additional results or information can be obtained upon request from the corresponding authors.

Supplemental Material

MMC S1. Supplement includes NRIXS data processing, mineral and rock properties along additional adiabats, and modeling details (PDF)

Additional Information

This article is part of a Special issue entitled: ‘SEDI 2024’ published in Physics of the Earth and Planetary Interiors.

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1-s2.0-S0031920125001608-mmc1.pdf

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Additional details

Related works

Is supplemented by
Dataset: 10.22002/8v9yv-9mm73 (DOI)

Funding

National Science Foundation
EAR-2303148
United States Department of Energy
DE-AC02-06CH11357
National Science Foundation
EAR-1661511
National Science Foundation
EAR-1634415
United States Department of Energy
DE-FG02-94ER14466
Japan Society for the Promotion of Science
23K19067
Japan Society for the Promotion of Science
24K00735

Dates

Submitted
2024-09-06
Accepted
2025-10-31
Available
2025-11-03
Available online
Available
2025-11-14
Version of record

Caltech Custom Metadata

Caltech groups
Seismological Laboratory, Division of Geological and Planetary Sciences (GPS)
Publication Status
Published