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Compressional behavior and spin state of δ-(Al,Fe)OOH at high pressures

Ohira, Itaru and Jackson, Jennifer M. and Solomatova, Natalia V. and Sturhahn, Wolfgang and Finkelstein, Gregory J. and Kamada, Seiji and Kawazoe, Takaaki and Maeda, Fumiya and Hirao, Naohisa and Nakano, Satoshi and Toellner, Thomas S. and Suzuki, Akio and Ohtani, Eiji (2019) Compressional behavior and spin state of δ-(Al,Fe)OOH at high pressures. American Mineralogist, 104 (9). pp. 1273-1284. ISSN 0003-004X.

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Hydrogen transport from the surface to the deep interior and distribution in the mantle are important in the evolution and dynamics of the Earth. An aluminum oxy-hydroxide, δ-AlOOH, might influence hydrogen transport in the deep mantle because of its high stability extending to lower mantle conditions. The compressional behavior and spin states of δ-(Al,Fe^(3+))OOH phases were investigated with synchrotron X-ray diffraction and Mössbauer spectroscopy under high pressure and room temperature. Pressure-volume (P-V) profiles of the δ-(Al_(0.908(9))^(57)Fe_(0.045(1)))OOH_(1.14(3)) [Fe/(Al+Fe) = 0.047(10), δ-Fe5] and the δ-(Al_(0.832(5))^(57)Fe_(0.117(1)))OOH_(1.15(3)) [Fe/(Al+Fe) = 0.123(2), δ-Fe12] show that these hydrous phases undergo two distinct structural transitions involving changes in hydrogen bonding environments and a high- to low-spin crossover in Fe^(3+). A change of axial compressibility accompanied by a transition from an ordered (P21nm) to disordered hydrogen bond (Pnnm) occurs near 10 GPa for both δ-Fe5 and δ-Fe12 samples. Through this transition, the crystallographic a and b axes become stiffer, whereas the c axis does not show such a change, as observed in pure δ-AlOOH. A volume collapse due to a transition from high- to low-spin states in the Fe^(3+) ions is complete below 32–40 GPa in δ-Fe5 and δ-Fe12, which i ~10 GPa lower than that reported for pure ε-FeOOH. Evaluation of the Mössbauer spectra of δ-(Al_(0.824(10))^(57)Fe_(0.126(4)))OOH_(1.15(4)) [Fe/(Al+Fe) = 0.133(3), δ-Fe13] also indicate a spin transition between 32–45 GPa. Phases in the δ-(Al,Fe)OOH solid solution with similar iron concentrations as those studied here could cause an anomalously high ρ/νΦ ratio (bulk sound velocity, defined as √ K/ρ at depths corresponding to the spin crossover region (~900 to ~1000 km depth), whereas outside the spin crossover region a low ρ/νΦ anomaly would be expected. These results suggest that the δ-(Al,Fe)OOH solid solution may play an important role in understanding the heterogeneous structure of the deep Earth.

Item Type:Article
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URLURL TypeDescription Information
Jackson, Jennifer M.0000-0002-8256-6336
Solomatova, Natalia V.0000-0002-2331-3427
Sturhahn, Wolfgang0000-0002-9606-4740
Finkelstein, Gregory J.0000-0001-7343-7527
Additional Information:© 2019 by the Mineralogical Society of America. Manuscript received November 30, 2018; Manuscript accepted May 13, 2019; Manuscript handled by Daniel Hummer. We thank Y. Ito for his help with polishing and operating the EPMA for the crystals used in this work. We also thank R. Njul for his help with polishing some of the samples. We are grateful to the editor D. Hummer and two anonymous reviewers for comments that helped to improve the manuscript. This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Science, Sport and Technology of the Japanese Government to I.O. (JSPS KAKENHI Grant Number: JP16J04690), to E.O. (Number: JP15H05748), to S.K. (Numbers: 26247089, 15H05831, and 16K13902), to A.S. (Numbers: JP15H05828 and JP19H01985). This work and I.O. were supported by the International Research and Training Group “Deep Earth Volatile Cycles” funded by the German Science Foundation (Grant Number: GRK 2156/1), the JSPS Japanese-German Graduate Externship, and the International Joint Graduate Program in Earth and Environmental Science (GP-EES), Tohoku University. This work was also partially supported by a grant from the W.M. Keck Institute for Space Studies and the National Science Foundation (NSF-CSEDIEAR-1600956) awarded to J.M.J. N.V.S. was partly funded by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement Number 681818–IMPACT). XRD measurements were performed at the BL10XU, SPring-8, Japan (proposal number: 2017A1650 to I.O., 2017A1251 to S.K., 2017A1673 to F.M., and 2015B0104, 2016A0104, and 2017B1514 to E.O.). SMS experiments were conducted at 3-ID-B, Advanced Photon Source, in the United States, which is partially supported by COMPRES. Deposit item AM-19-96913, CIF. Deposit items are free to all readers and found on the MSA website, via the specific issue’s Table of Contents (go to
Group:Keck Institute for Space Studies, Seismological Laboratory
Funding AgencyGrant Number
Ministry of Education, Culture, Sports, Science and Technology (MEXT)UNSPECIFIED
Japan Society for the Promotion of Science (JSPS)JP16J04690
Japan Society for the Promotion of Science (JSPS)JP15H05748
Japan Society for the Promotion of Science (JSPS)26247089
Japan Society for the Promotion of Science (JSPS)15H05831
Japan Society for the Promotion of Science (JSPS)16K13902
Japan Society for the Promotion of Science (JSPS)JP15H05828
Japan Society for the Promotion of Science (JSPS)JP19H01985
Deutsche Forschungsgemeinschaft (DFG)GRK 2156/1
Tohoku UniversityUNSPECIFIED
Keck Institute for Space Studies (KISS)UNSPECIFIED
European Research Council (ERC)681818
Subject Keywords:δ-AlOOH, δ-(Al,Fe)OOH, hydrous minerals, high-pressure, X-ray diffraction, Möss-bauer spectroscopy, diamond-anvil cell, synchrotron, water transport in the deep mantle
Issue or Number:9
Record Number:CaltechAUTHORS:20190904-100034357
Persistent URL:
Official Citation:Itaru Ohira, Jennifer M. Jackson, Natalia V. Solomatova, Wolfgang Sturhahn, Gregory J. Finkelstein, Seiji Kamada, Takaaki Kawazoe, Fumiya Maeda, Naohisa Hirao, Satoshi Nakano, Thomas S. Toellner, Akio Suzuki, Eiji Ohtani; Compressional behavior and spin state of δ-(Al,Fe)OOH at high pressures. American Mineralogist ; 104 (9): 1273–1284. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98407
Deposited By: Tony Diaz
Deposited On:04 Sep 2019 21:12
Last Modified:03 Oct 2019 21:40

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