Stable intermediate-spin ferrous iron in lower-mantle perovskite

Article metrics

Abstract

The lower mantle is dominated by a magnesium- and iron-bearing mineral with the perovskite structure. Iron has the ability to adopt different electronic configurations, and transitions in its spin state in the lower mantle can significantly influence mantle properties and dynamics. However, previous studies aimed at understanding these transitions have provided conflicting results1,2,3,4. Here we report the results of high-pressure (up to 110 GPa) and high-temperature (up to 1,000 K) experiments aimed at understanding spin transitions of iron in perovskite at lower-mantle conditions. Our Mössbauer and nuclear forward scattering data for two lower-mantle perovskite compositions demonstrate that the transition of ferrous iron from the high-spin to the intermediate-spin state occurs at approximately 30 GPa, and that high temperatures favour the stability of the intermediate-spin state. We therefore infer that ferrous iron adopts the intermediate-spin state throughout the bulk of the lower mantle. Our X-ray data show significant anisotropic compression of lower-mantle perovskite containing intermediate-spin ferrous iron, which correlates strongly with the spin transition. We predict spin-state heterogeneities in the uppermost part of the lower mantle associated with sinking slabs and regions of upwelling. These may affect local properties, including thermal and electrical conductivity, deformation (viscosity) and chemical behaviour, and thereby affect mantle dynamics.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: High-pressure 57Fe spectra of Mg0.88Fe0.12SiO3 perovskite.
Figure 2: Total spin number of iron in silicate perovskite.
Figure 3: Estimated Fe2+ spin-state distribution in the lower mantle.

References

  1. 1

    Badro, J. et al. Electronic transitions in perovskite: Possible non-convecting layers in the lower mantle. Science 305, 383–386 (2004).

  2. 2

    Li, J. et al. Electronic spin state of iron in lower mantle perovskite. Proc. Natl Acad. Sci. 101, 14027–14030 (2004).

  3. 3

    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).

  4. 4

    Li, J. et al. Pressure effect on the electronic structure of iron in (Mg,Fe)(Si,Al)O3 perovskite: A combined synchrotron Mössbauer and X-ray emission spectroscopy study up to 100 GPa. Phys. Chem. Mineral. 33, 575–585 (2006).

  5. 5

    Fyfe, W. S. The possibility of d-electron coupling in olivine at high pressures. Geochim. Cosmochim. Acta 19, 141–143 (1960).

  6. 6

    Lin, J. F., Jacobsen, S. D. & Wentzcovitch, R. M. Electronic spin transition of iron in the Earth’s deep mantle. Eos 88, 13–17 (2007).

  7. 7

    Fei, Y., Virgo, D., Mysen, B. O., Wang, Y. & Mao, H. K. Temperature dependent electron delocalization in (Mg,Fe)SiO3 perovskite. Am. Mineral. 79, 826–837 (1994).

  8. 8

    Lauterbach, S., McCammon, C. A., van Aken, P., Langenhorst, F. & Seifert, F. Mössbauer and ELNES spectroscopy of (Mg,Fe)(Si,Al)O3 perovskite: A highly oxidised component of the lower mantle. Contrib. Mineral. Petrol. 138, 17–26 (2000).

  9. 9

    Smirnov, G. V. General properties of nuclear resonant scattering. Hyperfine Interact. 123/124, 31–77 (1999).

  10. 10

    Lin, J. et al. Predominant intermediate-spin ferrous iron in lowermost mantle post-perovskite and perovskite. Nature Geosci. (this issue).

  11. 11

    Sturhahn, W., Jackson, J. M. & Lin, J. The spin state of iron in minerals of the Earth’s lower mantle. Geophys. Res. Lett. 32, doi:10.1029/2005GL022802 (2005).

  12. 12

    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).

  13. 13

    Stackhouse, S., Brodholt, J. P. & Price, G. D. Electronic spin transitions in iron-bearing MgSiO3 perovskite. Earth Planet. Sci. Lett. 253, 282–290 (2007).

  14. 14

    Bengtson, A., Persson, K. & Morgan, D. Ab initio study of the composition dependence of the pressure induced spin crossover in perovskite (Mg1−x,Fex)SiO3 . Earth Planet. Sci. Lett. 265, 535–545 (2008).

  15. 15

    Hofmeister, A. M. Is low-spin Fe2+ present in Earth’s mantle? Earth Planet. Sci. Lett. 243, 44–52 (2006).

  16. 16

    Fiquet, G., Dewaele, A., Andrault, D., Kunz, M. & Le Bihan, T. Thermoelastic properties and crystal structure of MgSiO3 perovskite at lower mantle pressure and temperature conditions. Geophys. Res. Lett. 27, 21–24 (2000).

  17. 17

    Brown, J. M. & Shankland, T. J. Thermodynamic parameters in the Earth as determined from seismic profiles. Geophys. J. R. Astron. Soc. 66, 579–596 (1981).

  18. 18

    Billen, M. I. Modeling the dynamics of subducting slabs. Annu. Rev. Earth Planet. Sci. 36, 325–356 (2008).

  19. 19

    Leng, W. & Zhong, S. Controls on plume heat flux and plume excess temperature. Geophys. Res. Lett. 113, doi:10.1029/2007JB005155 (2008).

  20. 20

    Mattern, E., Matas, J., Ricard, Y. & Bass, J. Lower mantle composition and temperature from mineral physics and thermodynamic modelling. Geophys. J. Int. 160, 973–990 (2005).

  21. 21

    Matas, J., Bass, J., Ricard, Y., Mattern, E. & Bukowinski, M. S. T. On the bulk composition of the lower mantle: Predictions and limitations from generalized inversion of radial seismic profiles. Geophys. J. Int. 170, 764–780 (2007).

  22. 22

    Ohta, K. et al. The electrical conductivity of post-perovskite in Earth’s D layer. Science 320, 89–91 (2008).

  23. 23

    Badro, J., Fiquet, G. & Guyot, F. in Earth’s Deep Mantle: Structure, Composition, and Evolution (eds van der Hilst, R. D., Bass, J., Matas, J. & Trampert, J.) 241–260 (American Geophysical Union, Washington, 2005).

  24. 24

    Carrez, P., Ferré, D. & Cordier, P. Implications for plastic flow in the deep mantle from modelling dislocations in MgSiO3 minerals. Nature 446, 68–70 (2007).

  25. 25

    Naliboff, J. B. & Kellogg, L. H. Can large increases in viscosity and thermal conductivity preserve large-scale heterogeneity in the mantle? Phys. Earth Planet. Inter. 161, 86–102 (2007).

  26. 26

    Lin, J.-F. et al. Spin transition zone in Earth’s lower mantle. Science 317, 1740–1743 (2007).

  27. 27

    Ruffer, R. & Chumakov, A. I. Hyperfine Interact. 97/98, 589–604 (1996).

Download references

Acknowledgements

We acknowledge the European Synchrotron Radiation Facility for provision of synchrotron radiation facilities (ID18 and ID27) and we would like to thank A. Chumakov and R. Rüffer for assistance in using beamline ID18 and V. Dmitriev for additional technical assistance. Use of the Advanced Photon Source (beamline 13-ID-D) was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. We are grateful to S. Übelhack and S. Linhardt for technical assistance at Bayerisches Geoinstitut. The project was partly supported by funds from the German Science Foundation (DFG) Priority Programme SPP1236 under project Mc 3/16-1.

Author information

All authors were involved in data collection, analysis and interpretation. C.M. wrote the paper.

Correspondence to C. McCammon or I. Kantor or J. Rouquette.

Supplementary information

Supplementary Information

Supplementary figures S1-S6 (PDF 529 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

McCammon, C., Kantor, I., Narygina, O. et al. Stable intermediate-spin ferrous iron in lower-mantle perovskite. Nature Geosci 1, 684–687 (2008) doi:10.1038/ngeo309

Download citation

Further reading