Altered chemistry of oxygen and iron under deep Earth conditions

A drastically altered chemistry was recently discovered in the Fe-O-H system under deep Earth conditions, involving the formation of iron superoxide (FeO 2 H x with x  = 0 to 1), but the puzzling crystal chemistry of this system at high pressures is largely unknown. Here we present evidence that des...

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Bibliographic Details
Published in:Nature communications 2019-01, Vol.10 (1), p.153-153, Article 153
Main Authors: Liu, Jin, Hu, Qingyang, Bi, Wenli, Yang, Liuxiang, Xiao, Yuming, Chow, Paul, Meng, Yue, Prakapenka, Vitali B., Mao, Ho-Kwang, Mao, Wendy L.
Format: Article
Language:English
Subjects:
639/638/263/915
639/766/119/1002
704/2151/209
Chemistry
Earth
GEOSCIENCES
H system
Humanities and Social Sciences
Hydrogen reduction
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Iron
Minerals
multidisciplinary
Organic chemistry
Oxygen
Science
Science (multidisciplinary)
Superoxide
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Summary:A drastically altered chemistry was recently discovered in the Fe-O-H system under deep Earth conditions, involving the formation of iron superoxide (FeO 2 H x with x  = 0 to 1), but the puzzling crystal chemistry of this system at high pressures is largely unknown. Here we present evidence that despite the high O/Fe ratio in FeO 2 H x , iron remains in the ferrous, spin-paired and non-magnetic state at 60–133 GPa, while the presence of hydrogen has minimal effects on the valence of iron. The reduced iron is accompanied by oxidized oxygen due to oxygen-oxygen interactions. The valence of oxygen is not –2 as in all other major mantle minerals, instead it varies around –1. This result indicates that like iron, oxygen may have multiple valence states in our planet’s interior. Our study suggests a possible change in the chemical paradigm of how oxygen, iron, and hydrogen behave under deep Earth conditions. Iron oxides prevail in the deep Earth, at extreme pressures and temperatures, with different stoichiometries than in ambient conditions. Here, high-pressure synchrotron X-ray spectroscopic measurements reveal the oxidation states of Fe and O in iron superoxide, shedding light on the puzzling chemistry of iron and oxygen in the deep Earth
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-018-08071-3