Journal Article

PUBDB-2026-03289

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Shielding of periclase by bridgmanite during compression of a polycrystalline mantle assemblage

Trautner, V. E.Extern* ; Koemets, E.Extern* ; Wang, B. ; Satta, N.Extern* ; Buchen, J.Extern* ; Hughes, G. M. ; Ledoux, E. E.Extern* ; Marquardt, K.Extern* ; Fei, H.Extern* ; Giordano, N.DESY* ; Katsura, T.Extern* ; Marquardt, H.Extern*

2026
de Gruyter Berlin

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Please use a persistent id in citations: doi:10.2138/am-2025-10040

Abstract: Earth’s lower mantle consists predominantly of two minerals, bridgmanite and Fe-bearing periclase, forming polycrystalline aggregates. Interpretation of seismic observations to constrain mantle temperature and composition requires a detailed understanding of the elastic behavior of mantle rocks. While the elastic properties of single-phase bridgmanite and periclase have been studied extensively, the bulk elastic properties of multiphase materials depend on how stress and strain are partitioned between the constituent phases, a process poorly understood.Here, we present high-pressure synchrotron X-ray diffraction data on a sintered polycrystal of bridgmanite and periclase with estimated volume proportions of 7:3 and a bulk composition of (Mg$_{0.91}$Fe$_{0.09}$)$_2$SiO$_4$, approximating a lower-mantle rock. We compare the compression behavior of the two-phase assemblage in quasi-hydrostatic conditions with and without high-temperature stress annealing. We find that bridgmanite forms a load-bearing framework, partially shielding periclase from the external confining pressure. During compression without annealing, this results in the development of under-pressure in the more compressible periclase. Consequently, the pressure-volume curve appears shallower relative to single-phase periclase and the onset of the iron spin crossover is suppressed, occurring at about 8 GPa higher external pressure. In contrast, when the two-phase assemblage is heated at 1800 K for around 1 minute, stresses are relaxed through plastic deformation and pressure is homogenized, producing compression curves consistent with single-phase measurements.Our results indicate that stress-strain partitioning in multiphase materials is highly temperature-dependent, with compression behavior moving from a regime close to the iso-strain bound towards the iso-stress bound with increasing temperature. The relative timescales of pressure variations and stress-relaxation likely determine the bulk elastic behavior of a multiphase mantle rock when a seismic wave passes. Future experimental investigations of the temperature- and frequency-dependence of stress-strain partitioning in bridgmanite-periclase aggregates are key to accurately model seismic properties of lower-mantle rocks.

Note: online first -- accepted manuscript version vorhanden

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Contributing Institute(s):

1. FS DOOR-User (FS DOOR-User)
2. PETRA-D (FS-PETRA-D)

Research Program(s):

1. 631 - Matter – Dynamics, Mechanisms and Control (POF4-631) (POF4-631)
2. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)
3. DEEP-MAPS - Deep Earth Mantle Phase Transition Maps: Studied by Time-Resolved Experiments (864877) (864877)
4. UltraLVP - Chemistry and transport properties of bridgmanite controlling lower-mantle dynamics (787527) (787527)

Experiment(s):

1. PETRA Beamline P02.2 (PETRA III)

Appears in the scientific report 2026

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Database coverage:
; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; Essential Science Indicators ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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