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Journal Article

Magnesiowüstite as a major nitrogen reservoir in Earth’s lowermost mantle

Authors

Rustioni,  G.
External Organizations;
GFZ SIMS Publications, Deutsches GeoForschungsZentrum;

/persons/resource/michawi

Wiedenbeck,  Michael
3.1 Inorganic and Isotope Geochemistry, 3.0 Geochemistry, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;
GFZ SIMS Publications, Deutsches GeoForschungsZentrum;

Miyajima,  N.
External Organizations;
GFZ SIMS Publications, Deutsches GeoForschungsZentrum;

Chanyshev,  A.
External Organizations;
GFZ SIMS Publications, Deutsches GeoForschungsZentrum;

Keppler,  H.
External Organizations;
GFZ SIMS Publications, Deutsches GeoForschungsZentrum;

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Fulltext (public)

5024490.pdf
(Publisher version), 5MB

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Citation

Rustioni, G., Wiedenbeck, M., Miyajima, N., Chanyshev, A., Keppler, H. (2024): Magnesiowüstite as a major nitrogen reservoir in Earth’s lowermost mantle. - Geochemical Perspectives Letters, 28, 43-47.
https://doi.org/10.7185/geochemlet.2401


Cite as: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5024490
Abstract
Ferropericlase (Mg,Fe)O is after bridgmanite the most abundant phase in the lower mantle. The ultralow velocity zones above the core-mantle boundary may contain very Fe-rich magnesiowüstite (Fe,Mg)O, possibly as result of the fractional crystallisation of a basal magma ocean. We have experimentally studied the solubility of nitrogen in the ferropericlase-magnesiowüstite solid solution series as function of iron content. Multi-anvil experiments were performed at 20–33 GPa and 1600–1800 °C in equilibrium with Fe metal. Nitrogen solubility increases from a few tens ppm (μg/g) for Mg-rich ferropericlase to more than 10 wt. % for nearly pure wüstite. Such high solubilities appear to be due to solid solution with NiAs-type FeN. Our data suggest that during fractional crystallisation of a magma ocean, the core-mantle boundary would have become extremely enriched with nitrogen, such that the deep mantle today could be the largest nitrogen reservoir on Earth. The often discussed “subchondritic N/C” ratio of the bulk silicate Earth may be an artefact of insufficient sampling of this deep reservoir.