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

Title data

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. Vol. 46 (2019) Issue 15 . - pp. 8731-8740.
ISSN 1944-8007
DOI: https://doi.org/10.1029/2019GL083613

Official URL:

Abstract in another language

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.

Further data

Item Type:	Article in a journal
Refereed:	Yes
Additional notes:	ISI:000483812500016
Institutions of the University:	Faculties > Faculty of Biology, Chemistry and Earth Sciences Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Inorganic Chemistry III Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Inorganic Chemistry III > Chair Inorganic Chemistry III - Univ.-Prof. Dr. Jürgen Senker Faculties
Result of work at the UBT:	Yes
DDC Subjects:	500 Science 500 Science > 540 Chemistry
Date Deposited:	25 Sep 2019 09:04
Last Modified:	18 May 2022 07:16
URI:	https://eref.uni-bayreuth.de/id/eprint/52427