Depth-dependent anisotropy in the Earth’s inner core linked to chemical stratification

Seismic anisotropy in the Earth's inner core (IC), including the heterogeneous, depth-dependent anisotropy structure, is a well-documented yet poorly understood feature plausibly related to the alignment of iron alloy crystals. Here, we report the effect of silicon and carbon on the plastic deformation of hexagonal close-packed (hcp) iron using radial X-ray diffraction at pressures up to 128 GPa and temperatures up to 1100 K. Our results reveal a low compressional wave anisotropy (~2 %) in the Fe-Si-C alloy, consistent with the seismic anisotropy observed in the outer regions of the IC. These findings, together with the higher anisotropy exhibited by pure hcp-Fe, suggest that the depth-dependent elastic anisotropy of the IC may originate from chemical stratification, i.e., radial gradients in silicon and carbon concentrations, during crystallization.

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Publication Details

Journal
Nature Communications
Published
2025-12-08
DOI
https://doi.org/10.1038/s41467-025-67067-y
Primary Topic
High-pressure geophysics and materials
Type
article
Field-Weighted Citation Impact
0.00

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article

Depth-dependent anisotropy in the Earth’s inner core linked to chemical stratification

Carmen Sanchez‐Valle, Stephan Klemme, Arno Rohrbach, Susanne Müller et al.
Nature Communications
High-pressure geophysics and materials
article

Depth-dependent anisotropy in the Earth’s inner core linked to chemical stratification

Carmen Sanchez‐Valle, Stephan Klemme, Arno Rohrbach, Susanne Müller, Efim Kolesnikov, Ilya Kupenko, Jasper Berndt, Hanns‐Peter Liermann, Xiang Li
article en

Abstract

Seismic anisotropy in the Earth's inner core (IC), including the heterogeneous, depth-dependent anisotropy structure, is a well-documented yet poorly understood feature plausibly related to the alignment of iron alloy crystals. Here, we report the effect of silicon and carbon on the plastic deformation of hexagonal close-packed (hcp) iron using radial X-ray diffraction at pressures up to 128 GPa and temperatures up to 1100 K. Our results reveal a low compressional wave anisotropy (~2 %) in the Fe-Si-C alloy, consistent with the seismic anisotropy observed in the outer regions of the IC. These findings, together with the higher anisotropy exhibited by pure hcp-Fe, suggest that the depth-dependent elastic anisotropy of the IC may originate from chemical stratification, i.e., radial gradients in silicon and carbon concentrations, during crystallization.

Nature CommunicationsVol. 16(1)
Centre National de la Recherche Scientifique (FR), University of Münster (DE), Université de Lille (FR), Deutsches Elektronen-Synchrotron DESY (DE), European Synchrotron Radiation Facility (FR), Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (FR), Unité Matériaux et Transformations (FR), École Centrale de Lille (FR)
European Commission, Deutsche Forschungsgemeinschaft, Deutsches Elektronen-Synchrotron
Openalex Percentile: Top 60%
High-pressure geophysics and materials
DOIOpen Access PDFOpenAlex
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