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Oxygen Vacancy Ordering in Aluminous Bridgmanite in the Earth's Lower Mantle
Author(s) -
Grüninger Helen,
Liu Zhaodong,
Siegel Renée,
Boffa Ballaran Tiziana,
Katsura Tomoo,
Senker Jürgen,
Frost Daniel J.
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl083613
Subject(s) - mantle (geology) , oxygen , vacancy defect , spectral line , spectroscopy , geology , mineralogy , crystallography , materials science , chemical physics , chemistry , geochemistry , physics , organic chemistry , quantum mechanics , astronomy
Oxygen vacancies (OVs), that charge‐balance the replacement of octahedrally coordinated Si 4+ by Al 3+ in the mineral bridgmanite, will influence transport properties in the lower mantle but little is known about their stability and local structure. Using 27 Al 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.