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Intermediate-spin ferrous iron in lowermost mantle post-perovskite and perovskite

Nature Geoscience volume 1, pages 688–691 (2008)Cite this article

Abstract

Iron-bearing silicate post-perovskite and perovskite are believed to be the dominant minerals of the lowermost mantle and the lower mantle, respectively. The electronic spin state of iron—a quantum property of every electron associated with its angular momentum—can strongly influence the properties of these mineral phases and thereby the nature of the Earth’s interior1,2,3,4,5,6,7,8,9,10,11,12,13,14,15. However, the spin state of iron at lowermost-mantle pressure/temperature conditions is poorly known16,17,18,19,20,21,22,23,24,25,26,27. Here we use in situ X-ray emission, X-ray diffraction and synchrotron Mössbauer spectroscopic techniques to measure the spin and valence states of iron in post-perovskite and perovskite at conditions relevant to the lowermost mantle25,28. We find that Fe2+ exists predominantly in the intermediate-spin state with a total spin number of one in both phases. We conclude that changes in the radiative thermal conductivity and iron partitioning in the lowermost mantle would thus be controlled by the structural transition from perovskite to post-perovskite, rather than the electronic transition of Fe2+.

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Figure 1: X-ray emission spectra of iron.
Figure 2: Representative X-ray diffraction patterns.
Figure 3: Average spin number of Fe2+.
Figure 4: Representative synchrotron Mössbauer spectra.

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Acknowledgements

We acknowledge GSECARS and XOR-3, APS, ANL for the use of the synchrotron and laser facilities. We thank J. Nalibof, E. J. Garnero, B. Maddox, W. Sturhahn, J. Lassiter and S. Grand for helpful discussions. Use of the Advanced Photon Source was supported by US Department of Energy, Office of Science, Basic Energy Sciences, under contract No. DE-AC02-06CH11357. GSECARS is supported by NSF Earth Sciences (EAR-0622171) and DOE Geosciences (DE-FG02-94ER14466). This work at Lawrence Livermore National Laboratory was carried out under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. J.F.L. was partially supported by the Lawrence Livermore Fellowship. G.V. acknowledges financial support from the Hungarian Research Fund (OTKA) under contract No. K72597 and from the Bolyai Fellowship. V.V.S. acknowledges financial support from DOE.

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Authors and Affiliations

  1. Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Texas 78712, USA

    Jung-Fu Lin

  2. Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA

    Heather Watson & William J. Evans

  3. KFKI Research Institute for Particle and Nuclear Physics, H-1525 Budapest, PO Box 49, Hungary

    György Vankó

  4. Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA

    Esen E. Alp & Jiyong Zhao

  5. Consortium for Advanced Radiation Sources, The University of Chicago, Chicago, Illinois 60637, USA

    Vitali B. Prakapenka, Przemek Dera & Atsushi Kubo

  6. Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd. NW, Washington, DC 20015, USA

    Viktor V. Struzhkin

  7. Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany

    Catherine McCammon

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Contributions

J.F.L., V.B.P., P.D., V.V.S. and A.K. contributed to the X-ray emission experiments, and J.F.L., E.E.A. and J.Z. contributed to the Mössbauer experiments. H.W. synthesized the starting sample. G.V. and E.E.A. contributed to X-ray emission and Mössbauer data analyses, respectively. All authors participated in the writing and revision of the paper.

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Correspondence to Jung-Fu Lin.

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Supplementary Information

Supplementary figures S1-S6 and table S1 (PDF 356 kb)

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Lin, JF., Watson, H., Vankó, G. et al. Intermediate-spin ferrous iron in lowermost mantle post-perovskite and perovskite. Nature Geosci 1, 688–691 (2008). https://doi.org/10.1038/ngeo310

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