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

Grüninger, Helen ORCIDiD
Liu, Zhaodong ORCIDiD
Siegel, Renée
Boffa Ballaran, Tiziana ORCIDiD
Katsura, Tomoo ORCIDiD
Senker, Jürgen ORCIDiD
Frost, Daniel J. ORCIDiD

DOI: https://doi.org/10.1029/2019GL083613
Persistent URL: http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/9080
Grüninger, Helen; Liu, Zhaodong; Siegel, Renée; Boffa Ballaran, Tiziana; Katsura, Tomoo; Senker, Jürgen; Frost, Daniel J., 2019: Oxygen Vacancy Ordering in Aluminous Bridgmanite in the Earth's Lower Mantle. In: Geophysical Research Letters, 46, 15, 8731-8740, DOI: https://doi.org/10.1029/2019GL083613. 

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 27Al 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.