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+.
Subscribe to Journal
Get full journal access for 1 year
only $15.58 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Garnero, E. J., Maupin, V., Lay, T. & Fouch, M. J. Variable azimuthal anisotropy in Earth’s lowermost mantle. Science 306, 259–261 (2004).
Hernlund, J. W., Thomas, C. & Tackley, P. J. A doubling of the post-perovskite phase boundary and structure of the Earth’s lowermost mantle. Nature 434, 882–886 (2005).
Lay, T., Hernlund, J., Garnero, E. J. & Thorne, M. S. A post-perovskite lens and D′′ heat flux beneath the central Pacific. Science 314, 1272–1276 (2006).
van der Hilst, R. D. et al. Seismostratigraphy and thermal structure of Earth’s core-mantle boundary region. Science 315, 1813–1817 (2007).
Murakami, M., Hirose, K., Kawamura, K., Sata, N. & Ohishi, Y. Post-perovskite phase transition in MgSiO3 . Science 304, 855–858 (2004).
Oganov, A. R. & Ono, S. Theoretical and experimental evidence for a post-perovskite phase of MgSiO3 in Earth’s D′′ layer. Nature 430, 445–448 (2004).
Merkel, S. et al. Plastic deformation of MgGeO3 post-perovskite at lower mantle pressures. Science 311, 644–646 (2006).
Matyska, C. & Yuen, D. A. The importance of radiative heat transfer on superplumes in the lower mantle with the new post-perovskite phase change. Earth Planet. Sci. Lett. 234, 71–81 (2005).
Matyska, C. & Yuen, D. A. Lower mantle dynamics with the post-perovskite phase change, radiative thermal conductivity, temperature- and depth-dependent viscosity. Phys. Earth Planet. Inter. 154, 196–207 (2006).
Naliboff, J. B. & Kellogg, L. H. Dynamic effects of a step-wise increase in thermal conductivity and viscosity in the lowermost mantle. Geophys. Res. Lett. 33, L12S09 (2006).
Buffett, B. A bound on heat flow below a double crossing of the perovskite-postperovskite phase transition. Geophys. Res. Lett. 34, L17302 (2007).
Hofmeister, A. M. & Yuen, D. A. Critical phenomena in thermal conductivity: Implications for lower mantle dynamics. J. Geodyn. 44, 186–199 (2007).
Mao, W. L. et al. Ferromagnesian postperovskite silicates in the D′′ layer of the Earth. Proc. Natl Acad. Sci. USA 101, 15867–15869 (2004).
Kobayashi, Y. et al. Fe–Mg partitioning between (Mg,Fe)SiO3 post-perovskite, perovskite, and magnesiowüstite in the Earth’s lower mantle. Geophys. Res. Lett. 32, L19302 (2005).
Murakami, M., Hirose, K., Sata, N. & Ohishi, Y. Post-perovskite phase transition and mineral chemistry in the pyrolitic lowermost mantle. Geophys. Res. Lett. 32, L03304 (2005).
Lin, J. F., Jacobsen, S. D. & Wentzcovitch, R. M. Electronic spin transition of iron in the Earth’s deep mantle. Eos Trans. Am. Geophys. Union 88, 13–17 (2007).
Badro, J. et al. Electronic transitions in perovskite: Possible nonconvecting layers in the lower mantle. Science 305, 383–386 (2004).
Li, J. et al. Electronic spin state of iron in lower mantle perovskite. Proc. Natl Acad. Sci. USA 101, 14027–14030 (2004).
Jackson, J. M. et al. A synchrotron Mössbauer spectroscopy study of (Mg,Fe)SiO3 perovskite up to 120 GPa. Am. Mineral. 90, 199–205 (2005).
Goncharov, A. F., Struzhkin, V. V. & Jacobsen, S. D. Reduced radiative conductivity of low-spin (Mg,Fe)O in the lower mantle. Science 312, 1205–1208 (2006).
Stackhouse, S., Brodholt, J., Dobson, D. P. & Price, G. D. Electronic spin transitions and the seismic properties of ferrous iron bearing MgSiO3 post-perovskite. Geophys. Res. Lett. 33, L12S03 (2006).
Zhang, F. & Oganov, A. R. Valence state and spin transitions of iron in Earth’s mantle silicates. Earth Planet. Sci. Lett. 249, 436–443 (2006).
Bengtson, A., Persson, K. & Morgan, D. Ab initio study of the composition dependence of the pressure-induced spin transition in the (Mg1−x,Fex)SiO3 system. Earth Planet. Sci. Lett. 265, 535–545 (2008).
Keppler, H., Kantor, I. & Dubrovinsky, L. S. Optical absorption spectra of ferropericlase to 84 GPa. Am. Mineral. 92, 433–436 (2007).
Lin, J. F. et al. Spin transition zone in Earth’s lower mantle. Science 317, 1740–1743 (2007).
McCammon, C. et al. Intermediate-spin ferrous iron in lower mantle perovskite. Nature Geosci.doi:10.1038/ngeo309 (2008).
Stackhouse, S., Brodholt, J. P. & Price, G. D. Electronic spin transitions in iron-bearing MgSiO3 perovskite. Earth Planet. Sci. Lett. 253, 282–290 (2007).
Sturhahn, W. Nuclear resonant spectroscopy. J. Phys. Condens. Matter 16, S497–S530 (2004).
Fei, Y. et al. Toward an internally consistent pressure scale. Proc. Natl Acad. Sci. USA 104, 9182–9186 (2007).
Vankó, G. et al. Probing the 3d spin momentum with X-ray emission spectroscopy: The case of molecular-spin transitions. J. Phys. Chem. B 110, 11647–11653 (2006).
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.
About this article
Cite this article
Lin, J., Watson, H., Vankó, G. et al. Intermediate-spin ferrous iron in lowermost mantle post-perovskite and perovskite. Nature Geosci 1, 688–691 (2008) doi:10.1038/ngeo310
Journal of Geophysical Research: Solid Earth (2019)
Iron isotopic fractionation in mineral phases from Earth's lower mantle: Did terrestrial magma ocean crystallization fractionate iron isotopes?
Earth and Planetary Science Letters (2019)
Physical and chemical properties of the mantle minerals explored by high-pressure and high-temperature experiments
Japanese Magazine of Mineralogical and Petrological Sciences (2019)
Combining X-ray Kβ1,3, valence-to-core, and X-ray Raman spectroscopy for studying Earth materials at high pressure and temperature: the case of siderite
Journal of Analytical Atomic Spectrometry (2019)
Nature Communications (2018)