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The stability of Fe (sub 5) O (sub 6) and Fe (sub 4) O (sub 5) at high pressure and temperature

Koutaro Hikosaka, Ryosuke Sinmyo, Kei Hirose, Takayuki Ishii and Yasuo Ohishi
The stability of Fe (sub 5) O (sub 6) and Fe (sub 4) O (sub 5) at high pressure and temperature
American Mineralogist (September 2019) 104 (9): 1356-1359


The oxygen fugacity in the interior of the Earth is largely controlled by iron-bearing minerals. Recent studies have reported various iron oxides with chemical compositions between FeO and Fe3O4 above ~10 GPa. However, the stabilities of these high-pressure iron oxides remain mostly uninvestigated. In this study, we performed in situ X-ray diffraction (XRD) measurements in a laser-heated diamond-anvil cell (DAC) to determine the phase relations in both Fe5O6 and Fe4O5 bulk compositions to 61 GPa and to 2720 K. The results show that Fe5O6 is a high-temperature phase stable above 1600 K and ~10 GPa, while FeO + Fe4O5 are formed at relatively low temperatures. We observed the decomposition of Fe5O6 into 2FeO + Fe3O4 above 38 GPa and the decomposition of Fe4O5 into FeO + h-Fe3O4 at a similar pressure range. The coexistence of FeO and Fe3O4 indicates that none of the recently discovered compounds between FeO and Fe3O4 (i.e., Fe5O6, Fe9O11, Fe4O5, and Fe7O9) are formed beyond ~40 GPa at 1800 K, corresponding to conditions in the shallow lower mantle. Additionally, as some superdeep diamonds have genetic links with these high-pressure iron oxides, our results give constraints on pressure and temperature conditions of their formation.

ISSN: 0003-004X
EISSN: 1945-3027
Serial Title: American Mineralogist
Serial Volume: 104
Serial Issue: 9
Title: The stability of Fe (sub 5) O (sub 6) and Fe (sub 4) O (sub 5) at high pressure and temperature
Affiliation: University of Tokyo, Department of Earth and Planetary Science, Tokyo, Japan
Pages: 1356-1359
Published: 201909
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 18
Accession Number: 2019-082817
Categories: Geophysics of minerals and rocks
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Secondary Affiliation: Tokyo Institute of Technology, JPN, JapanUniversitaet Bayreuth, DEU, GermanyJapan Synchrotron Radiation Research Institute, JPN, Japan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201944
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