Journal Article

PUBDB-2024-00741

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Thermal Equation of State and Structural Evolution of Al‐Bearing Bridgmanite

Criniti, G. (Corresponding author)Extern* ; Boffa Ballaran, T.Extern* ; Kurnosov, A.Extern* ; Liu, Z. ; Glazyrin, K.XFEL.EU*DESY* ; Merlini, M.Extern* ; Hanfland, M. ; Frost, D. J.Extern*

2024
Wiley Hoboken, NJ

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Please use a persistent id in citations: doi:10.1029/2023JB026879  doi:10.3204/PUBDB-2024-00741

Abstract: (Mg, Fe, Al)(Si, Al)O$_{3}$ bridgmanite is the most abundant mineral of Earth's lower mantle. Al is incorporated in the crystal structure of bridgmanite through the Fe$^{3+}$AlO$_{3}$ and AlAlO$_{3}$ charge coupled (CC) mechanisms, and the MgAlO$_{2.5}$ oxygen vacancy (OV) mechanism. Oxygen vacancies are believed to cause a substantial decrease of the bulk modulus of aluminous bridgmanite based on first-principles calculations on the MgAlO$_{2.5}$ end-member. However, there is no conclusive experimental evidence supporting this hypothesis due to the uncertainties on the chemical composition, crystal chemistry, and/or high-pressure behavior of samples analyzed in previous studies. Here, we synthesized high-quality single crystals of bridgmanite in the MgO–AlO$_{1.5}$–SiO$_{2}$ system with different bulk Al contents and degrees of CC and OV substitutions. Suitable crystals with different compositions were loaded in resistively heated diamond anvil cells and analyzed by synchrotron X-ray diffraction at pressures up to approximately 80 GPa at room temperature and 35 GPa at temperatures up to 1,000 K. Single-crystal structural refinements at high pressure show that the compressibility of bridgmanite is mainly controlled by Al–Si substitution in the octahedral site and that oxygen vacancies in bridgmanite have no detectable effect on the bulk modulus in the compositional range investigated here, which is that relevant to a pyrolytic lower mantle. The proportion of oxygen vacancies in Al-bearing bridgmanite has been calculated using a thermodynamic model constrained using experimental data at 27 GPa and 2,000 K for an Fe-free system and extrapolated to pressures equivalent to 1,250 km depth using the thermoelastic parameters of Al-bearing bridgmanite determined in this study.

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Contributing Institute(s):

1. DOOR-User (DOOR ; HAS-User)
2. Experimentebetreuung PETRA III (FS-PET-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. FS-Proposal: I-20200330 (I-20200330) (I-20200330)
4. FS-Proposal: I-20210333 (I-20210333) (I-20210333)

Experiment(s):

1. PETRA Beamline P02.2 (PETRA III)

Appears in the scientific report 2024

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Database coverage:
; ; ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; DEAL Wiley ; Ebsco Academic Search ; Essential Science Indicators ; IF < 5 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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