期刊
NATURE
卷 551, 期 7681, 页码 494-+出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/nature24461
关键词
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资金
- Department of Energy (DOE)-NNSA [DE-NA0001974]
- NSF
- DOE-BES/DMSE [DE-FG02-99ER45775]
- National Science Foundation (NSF)-Earth Sciences [EAR-1128799]
- DOE Geosciences [DE-FG02-94ER14466]
- US DOE, Office of Science, Office of Basic Energy Sciences [DE-AC02-06CH11357]
- Geophysics Program by the NSF [EAR 1446969]
- Deep Carbon Observatory
- NSF [EAR-1345112, EAR-1447438]
- National Natural Science Foundation of China [U1530402]
- Natural Science Foundation of China [41590621]
- State Key Development Program of Basic Research of China [2014CB845905]
- Division Of Earth Sciences
- Directorate For Geosciences [1446969] Funding Source: National Science Foundation
Ultralow-velocity zones (ULVZs) at Earth's core-mantle boundary region have important implications for the chemical composition and thermal structure of our planet, but their origin has long been debated(1-3). Hydrogen-bearing iron peroxide (FeO2Hx) in the pyrite-type crystal structure was recently found to be stable under the conditions of the lowermost mantle(4-6). Using high-pressure experiments and theoretical calculations, we find that iron peroxide with a varying amount of hydrogen has a high density and high Poisson ratio as well as extremely low sound velocities consistent with ULVZs. Here we also report a reaction between iron and water at 86 gigapascals and 2,200 kelvin that produces FeO2Hx. This would provide a mechanism for generating the observed volume occupied by ULVZs through the reaction of about one-tenth the mass of Earth's ocean water in subducted hydrous minerals with the effectively unlimited reservoir of iron in Earth's core. Unlike other candidates for the composition of ULVZs(7-12), FeO2Hx synthesized from the superoxidation of iron by water would not require an extra transportation mechanism to migrate to the core-mantle boundary. These dense FeO2Hx-rich domains would be expected to form directly in the core-mantle boundary region and their properties would provide an explanation for the many enigmatic seismic features that are observed in ULVZs(1,13,14).
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