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A doubling of the post-perovskite phase boundary and structure of the Earth's lowermost mantle


The thermal structure of the Earth's lowermost mantle—the D″ layer spanning depths of 2,600–2,900 kilometres1—is key to understanding the dynamical state and history of our planet. Earth's temperature profile (the geotherm) is mostly constrained by phase transitions, such as freezing at the inner-core boundary or changes in crystal structure within the solid mantle, that are detected as discontinuities in seismic wave speed and for which the pressure and temperature conditions can be constrained by experiment and theory. A recently discovered phase transition at pressures of the D″ layer2,3,4 is ideally situated to reveal the thermal structure of the lowermost mantle, where no phase transitions were previously known to exist. Here we show that a pair of seismic discontinuities observed in some regions of D″ can be explained by the same phase transition as the result of a double-crossing of the phase boundary by the geotherm at two different depths. This simple model can also explain why a seismic discontinuity is not observed in some other regions, and provides new constraints for the magnitude of temperature variations within D″.

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Figure 1: The relationship between the geotherm and pPv phase boundary for different core temperatures (a), and corresponding seismic shear-wave profiles (b).
Figure 2: The relationship between three schematic geotherms and the pPv phase boundary (a), corresponding vS profiles (b), and a sketch of possible lower-mantle structures (c).
Figure 3: Comparison of data (a) with synthetic shear-wave seismograms calculated for the cold (b), warm (c), and hot (d) vS profiles shown in Fig. 2b.
Figure 4: Summary of the migration results for the synthetic cold-mantle (left column) and warm-mantle (centre column) vS profiles along with real data (right column) using the traces shown in Fig. 3.

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  1. Bullen, K. E. Compressibility-pressure hypothesis and the Earth's interior. Mon. Not. R. Astron. Soc. Geophys. Suppl. 5, 355–368 (1949)

    ADS  Google Scholar 

  2. Murakami, M., Hirose, K., Sata, N., Ohishi, Y. & Kawamura, K. Phase transition of MgSiO3 perovskite in the deep lower mantle. Science 304, 855–858 (2004)

    Article  ADS  CAS  Google Scholar 

  3. 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)

    Article  ADS  CAS  Google Scholar 

  4. Tsuchiya, T., Tsuchiya, J., Umemoto, K. & Wentzcovitch, R. M. Phase transition in MgSiO3 perovskite in the earth's lower mantle. Earth Planet. Sci. Lett. 224, 241–248 (2004)

    Article  ADS  CAS  Google Scholar 

  5. Lay, T. & Helmberger, D. V. A shear velocity discontinuity in the lower mantle. Geophys. Res. Lett. 10, 63–66 (1983)

    Article  ADS  Google Scholar 

  6. Wysession, M. et al. The Core-Mantle Boundary Region 273–298 (American Geophysical Union, Washington, DC, 1998)

    Book  Google Scholar 

  7. Sidorin, I., Gurnis, M., Helmberger, D. V. & Ding, X. Interpreting D″ seismic structure using synthetic waveforms computed from dynamic models. Earth Planet. Sci. Lett. 163, 31–41 (1998)

    Article  ADS  CAS  Google Scholar 

  8. Boehler, R. High-pressure experiments and the phase diagram of lower mantle and core constituents. Rev. Geophys. 38, 221–245 (2000)

    Article  ADS  CAS  Google Scholar 

  9. Alfè, D., Gillan, M. J. & Price, G. D. Composition and temperature of the Earth's core constrained by combining ab initio calculations and seismic data. Earth Planet. Sci. Lett. 195, 91–98 (2002)

    Article  ADS  Google Scholar 

  10. Thomas, C., Kendall, J. & Lowman, J. Lower-mantle seismic discontinuities and the thermal morphology of subducted slabs. Earth Planet. Sci. Lett. 225, 105–113 (2004)

    Article  ADS  CAS  Google Scholar 

  11. Thomas, C., Garnero, E. J. & Lay, T. High-resolution imaging of lowermost mantle structure under the Cocos plate. J. Geophys. Res. 109, B08307 (2004)

    Article  ADS  Google Scholar 

  12. Müller, G. The reflectivity method: A tutorial. Z. Geophys. 58, 153–174 (1985)

    ADS  Google Scholar 

  13. Stacey, F. Physics of the Earth 3rd edn, appendix G (Brookfield, Kenmore, Queensland, 1992)

    Google Scholar 

  14. Buffett, B. A. Estimates of heat flow in the deep mantle based on the power requirements for the geodynamo. Geophys. Res. Lett. 29, GL014649 (2002)

    Article  Google Scholar 

  15. Christensen, U. R. & Tilgner, A. Power requirement of the geodynamo from ohmic losses in numerical and laboratory dynamos. Nature 429, 169–171 (2004)

    Article  ADS  CAS  Google Scholar 

  16. Lithgow-Bertelloni, C. & Richards, M. A. The dynamics of Cenozoic and Mesozoic plate motions. Rev. Geophys. 36, 27–78 (1998)

    Article  ADS  Google Scholar 

  17. Nakagawa, T. & Tackley, P. J. Effects of a perovskite-post perovskite phase change near the core-mantle boundary in compressible mantle convection. Geophys. Res. Lett. 31, L16611 (2004)

    Article  ADS  Google Scholar 

  18. Aizawa, Y. et al. Temperature derivatives of elastic moduli of MgSiO3 perovskite. Geophys. Res. Lett. 31, L01602 (2004)

    ADS  Google Scholar 

  19. Dziewonski, A. M. & Anderson, D. L. Preliminary reference earth model. Phys. Earth Planet. Inter. 25, 297–356 (1981)

    Article  ADS  Google Scholar 

  20. Kennett, B. L. N., Engdahl, E. R. & Buland, R. Constraints on seismic velocities in the Earth from travel times. Geophys. J. Int. 122, 108–124 (1995)

    Article  ADS  Google Scholar 

Download references


This collaboration was facilitated by the Meeting of Young Researchers in the Earth Sciences (MYRES) held in La Jolla, California, in August 2004. This work was supported by a grant from IGPP Los Alamos.

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Correspondence to John W. Hernlund.

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Hernlund, J., Thomas, C. & Tackley, P. A doubling of the post-perovskite phase boundary and structure of the Earth's lowermost mantle. Nature 434, 882–886 (2005).

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