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

Autor: Helen Grüninger, Zhaodong Liu, Renée Siegel, Tiziana Boffa Ballaran, Tomoo Katsura, Jürgen Senker, Daniel J. Frost
Jazyk: angličtina
Rok vydání: 2019
Předmět:
Zdroj: Geophysical Research Letters, Vol 46, Iss 15, Pp 8731-8740 (2019)
Druh dokumentu: article
ISSN: 1944-8007
0094-8276
DOI: 10.1029/2019GL083613
Popis: 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.
Databáze: Directory of Open Access Journals
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