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Oxygen Vacancy Ordering in Aluminous Bridgmanite in the Earth's Lower Mantle

Titelangaben

Grüninger, Helen ; Liu, Zhaodong ; Siegel, Renée ; Boffa Ballaran, Tiziana ; Katsura, Tomoo ; Senker, Jürgen ; Frost, Daniel J.:
Oxygen Vacancy Ordering in Aluminous Bridgmanite in the Earth's Lower Mantle.
In: Geophysical Research Letters. Bd. 46 (2019) Heft 15 . - S. 8731-8740.
ISSN 1944-8007
DOI: https://doi.org/10.1029/2019GL083613

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Abstract

Oxygen vacancies (OVs), that charge-balance the replacement of octahedrally coordinated Si4+ by Al3+ in the mineral bridgmanite, will influence transport properties in the lower mantle but little is known about their stability and local structure. Using Al-27 nuclear magnetic resonance (NMR) spectroscopy we have characterized OVs within six aluminous bridgmanite samples. In the resulting NMR spectra sixfold, fivefold, and fourfold coordinated Al species are resolved, in addition to near eightfold coordinated Al substituting for Mg. Fivefold coordinated Al is formed by single OV sites but fourfold coordination must result from short range ordering of OVs, producing OV clusters that may form through migration into twin domain walls. Characterizing the occurrence of such OV structures is an important prerequisite for understanding how transport properties change with depth and composition in the lower mantle. Plain Language Summary The lower mantle encompasses the largest region of the Earth's interior and is mainly composed of the perovskite-structured mineral (Mg,Fe,Al)(Al,Si)O-3 bridgmanite. Its properties, therefore, control both the diffusive transport of elements and solid state flow in the lower mantle, which will be strongly influenced by point defects. We have identified and quantified defects in bridgmanite that arise from the replacement of silicon by aluminum and result in the creation of a vacant oxygen site. These oxygen defects are also found to form clusters in the structure, which in other perovskite structured minerals have been shown to strongly affect physical properties. As defect formation and ordering is dependent on composition and pressure, strong variations in physical properties may be expected within the upper 300 km of the lower mantle.

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Publikationsform: Artikel in einer Zeitschrift
Begutachteter Beitrag: Ja
Zusätzliche Informationen: ISI:000483812500016
Institutionen der Universität: Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Chemie
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Chemie > Lehrstuhl Anorganische Chemie III
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Chemie > Lehrstuhl Anorganische Chemie III > Lehrstuhl Anorganische Chemie III - Univ.-Prof. Dr. Jürgen Senker
Fakultäten
Titel an der UBT entstanden: Ja
Themengebiete aus DDC: 500 Naturwissenschaften und Mathematik
500 Naturwissenschaften und Mathematik > 540 Chemie
Eingestellt am: 25 Sep 2019 09:04
Letzte Änderung: 18 Mai 2022 07:16
URI: https://eref.uni-bayreuth.de/id/eprint/52427