Ferrous Iron Under Oxygen-Rich Conditions in the Deep Mantle.
Geophys Res Lett
; 46(3): 1348-1356, 2019 Feb 16.
Article
em En
| MEDLINE
| ID: mdl-31007309
ABSTRACT
Recent experiments have demonstrated the existence of previously unknown iron oxides at high pressure and temperature including newly discovered pyrite-type FeO2 and FeO2Hx phases stable at deep terrestrial lower mantle pressures and temperatures. In the present study, we probed the iron oxidation state in high-pressure transformation products of Fe3+OOH goethite by in situ X-ray absorption spectroscopy in laser-heated diamond-anvil cell. At pressures and temperatures of ~91 GPa and 1,500-2,350 K, respectively, that is, in the previously reported stability field of FeO2Hx, a measured shift of -3.3 ± 0.1 eV of the Fe K-edge demonstrates that iron has turned from Fe3+ to Fe2+. We interpret this reductive valence change of iron by a concomitant oxidation of oxygen atoms from O2- to O-, in agreement with previous suggestions based on the structures of pyrite-type FeO2 and FeO2Hx phases. Such peculiar chemistry could drastically change our view of crystal chemistry in deep planetary interiors.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
Geophys Res Lett
Ano de publicação:
2019
Tipo de documento:
Article