Mid-mantle water transportation implied by the electrical and seismic properties of ε-FeOOH

Yukai Zhuang; Bo Gan; Zhongxun Cui; Ruilian Tang; Renbiao Tao; Mingqiang Hou; Gang Jiang; Catalin Popescu; Gaston Garbarino; Youjun Zhang; Qingyang Hu

doi:10.1016/j.scib.2021.12.002

Mid-mantle water transportation implied by the electrical and seismic properties of ε-FeOOH

Sci Bull (Beijing). 2022 Apr 15;67(7):748-754. doi: 10.1016/j.scib.2021.12.002. Epub 2021 Dec 4.

Authors

Yukai Zhuang¹, Bo Gan², Zhongxun Cui³, Ruilian Tang⁴, Renbiao Tao³, Mingqiang Hou⁵, Gang Jiang², Catalin Popescu⁶, Gaston Garbarino⁷, Youjun Zhang⁸, Qingyang Hu⁹

Affiliations

¹ Center for High Pressure Science and Technology Advanced Research, Beijing 100094, China; Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China.
² Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China.
³ Center for High Pressure Science and Technology Advanced Research, Beijing 100094, China.
⁴ Center for High Pressure Science and Technology Advanced Research, Beijing 100094, China; School of Materials Science and Engineering, Changchun University of Science and Technology, Changchun 130022, China.
⁵ State Key Laboratory of Geodesy and Earth's Dynamics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430077, China.
⁶ Consorcio para la Construcción, Equipamiento y Explotación del Laboratorio de Luz de Sincrotrón, Cerdanyola del Vallès, Barcelona 08290, Spain.
⁷ European Synchrotron Radiation Facility, Grenoble 38000, France.
⁸ Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China; International Center for Planetary Science, College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China. Electronic address: zhangyoujun@scu.edu.cn.
⁹ Center for High Pressure Science and Technology Advanced Research, Beijing 100094, China; Center for Excellence in Deep Earth Science, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China. Electronic address: qingyang.hu@hpstar.ac.cn.

PMID: 36546139
DOI: 10.1016/j.scib.2021.12.002

Abstract

Water in the mantle transition zone and the core-mantle boundary plays a key role in Earth's stratification, volatile cycling, and core formation. If water transportation is actively running between the aforementioned layers, the lower mantle should contain water channels with distinctive seismic and/or electromagnetic signatures. Here, we investigated the electrical conductivity and sound velocity of ε-FeOOH up to 71 GPa and 1800 K and compared them with global tomography data. An abrupt three-order jump of electrical conductivity was observed above 50 GPa, reaching 1.24(12) × 10³ S/m at 61 GPa. Meanwhile, the longitudinal sound velocity dropped by 16.8% in response to the high-to-low spin transition of Fe³⁺. The high-conductivity and low-sound velocity of ε-FeOOH match the features of heterogenous scatterers in the mid-lower mantle. Such unique properties of hydrous ε-FeOOH, or possibly other Fe-enriched phases can be detected as evidence of active water transportation in the mid-lower mantle.

Keywords: Electrical conductivity; Heterogeneity; Mid-lower mantle; Seismic velocity.