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Title: Dehydrogenation of goethite in Earth’s deep lower mantle

Authors:
; ; ; ; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1341909
Grant/Contract Number:
FG02-99ER45775
Resource Type:
Journal Article: Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 114; Journal Issue: 7; Related Information: CHORUS Timestamp: 2017-06-25 05:28:43; Journal ID: ISSN 0027-8424
Publisher:
Proceedings of the National Academy of Sciences
Country of Publication:
United States
Language:
English

Citation Formats

Hu, Qingyang, Kim, Duck Young, Liu, Jin, Meng, Yue, Yang, Liuxiang, Zhang, Dongzhou, Mao, Wendy L., and Mao, Ho-kwang. Dehydrogenation of goethite in Earth’s deep lower mantle. United States: N. p., 2017. Web. doi:10.1073/pnas.1620644114.
Hu, Qingyang, Kim, Duck Young, Liu, Jin, Meng, Yue, Yang, Liuxiang, Zhang, Dongzhou, Mao, Wendy L., & Mao, Ho-kwang. Dehydrogenation of goethite in Earth’s deep lower mantle. United States. doi:10.1073/pnas.1620644114.
Hu, Qingyang, Kim, Duck Young, Liu, Jin, Meng, Yue, Yang, Liuxiang, Zhang, Dongzhou, Mao, Wendy L., and Mao, Ho-kwang. Tue . "Dehydrogenation of goethite in Earth’s deep lower mantle". United States. doi:10.1073/pnas.1620644114.
@article{osti_1341909,
title = {Dehydrogenation of goethite in Earth’s deep lower mantle},
author = {Hu, Qingyang and Kim, Duck Young and Liu, Jin and Meng, Yue and Yang, Liuxiang and Zhang, Dongzhou and Mao, Wendy L. and Mao, Ho-kwang},
abstractNote = {},
doi = {10.1073/pnas.1620644114},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 7,
volume = 114,
place = {United States},
year = {Tue Jan 31 00:00:00 EST 2017},
month = {Tue Jan 31 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1073/pnas.1620644114

Citation Metrics:
Cited by: 11works
Citation information provided by
Web of Science

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  • The cycling of hydrogen influences the structure, composition, and stratification of Earth’s interior. Our recent discovery of pyrite-structured iron peroxide (designated as the P phase) and the formation of the P phase from dehydrogenation of goethite FeO 2H implies the separation of the oxygen and hydrogen cycles in the deep lower mantle beneath 1,800 km. Here we further characterize the residual hydrogen, x, in the P-phase FeO 2Hx. Using a combination of theoretical simulations and high-pressure–temperature experiments, we calibrated the x dependence of molar volume of the P phase. Within the current range of experimental conditions, we observed a compositionalmore » range of P phase of 0.39 < x < 0.81, corresponding to 19–61% dehydrogenation. Increasing temperature and heating time will help release hydrogen and lower x, suggesting that dehydrogenation could be approaching completion at the high-temperature conditions of the lower mantle over extended geological time. Our observations indicate a fundamental change in the mode of hydrogen release from dehydration in the upper mantle to dehydrogenation in the deep lower mantle, thus differentiating the deep hydrogen and hydrous cycles.« less
  • Core formation represents the most significant differentiation event in Earth’s history. Our planet’s present layered structure with a metallic core and an overlying mantle implies that there must be a mechanism to separate iron alloy from silicates in the initially accreted material. At upper mantle conditions, percolation has been ruled out as an efficient mechanism because of the tendency of molten iron to form isolated pockets at these pressures and temperatures. Here we present experimental evidence of a liquid iron alloy forming an interconnected melt network within a silicate perovskite matrix under pressure and temperature conditions of the Earth’s lowermore » mantle. Using nanoscale synchrotron X-ray computed tomography, we image a marked transition in the shape of the iron-rich melt in three-dimensional reconstructions of samples prepared at varying pressures and temperatures using a laser-heated diamond-anvil cell. We find that, as the pressure increases from 25 to 64GPa, the iron distribution changes from isolated pockets to an interconnected network. Our results indicate that percolation could be a viable mechanism of core formation at Earth’s lower mantle conditions.« less