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Shear-induced material transfer across the core-mantle boundary aided by the post-perovskite phase transition

Abstract

We present a novel mechanical model for the extraction of outer core material upwards across the CMB into the mantle side region of D” and subsequent interaction with the post-perovskite (ppv) phase transition. A strong requirement of the model is that the D” region behaves as a poro-viscoelastic granular material with dilatant properties. Using new ab-initio estimates of the ppv shear modulus, we show how shear-enhanced dilation promoted by downwelling mantle sets up an instability that drives local fluid flow. If loading rates locally exceed c. 10−12 s−1, calculated core metal upwelling rates are >10−4 m/s, far in excess of previous estimates based on static percolation or capillary flow. Associated mass flux rates are sufficient to deliver 0.5% outer core mass to D” in < 106 yr, provided the minimum required loading rate is maintained. Core metal transported upwards into D” may cause local rapid changes in electrical and thermal conductivity and rheology that if preserved, may account for some of the observed small wavelength heterogeneties (e.g. PKP scattering) there.

References

  1. Alfe, D., G. D. Price, and M. J. Gillan, 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  Google Scholar 

  2. Biot, M. A., General theory of three dimensional consolidation, J. Appl. Phys., 12, 155–164, 1941.

    Article  Google Scholar 

  3. Brandon, A. D., R. J. Walker, I. S. Puchtel, H. Becker, M. Humayun, and S. Revillon, 186Os-187Os systematics of Gorgona Island komatiites: Implications for early growth of the inner core, Earth Planet. Sci. Lett., 206, 411–426, 2003.

    Article  Google Scholar 

  4. Buffett, B. A., E. J. Garnero, and R. Jeanolz, Sediments at the top of the Earth’s core, Science, 290, 1338–1342, 2000.

    Article  Google Scholar 

  5. Bruhn, D., N. Groebner, and D. L. Kohlstedt, An interconnected network of core-forming melts produced by shear deformation, Nature, 403, 883–886, 2000.

    Article  Google Scholar 

  6. Garnero, E. J., Heterogeneities in the lowermost mantle, Annu. Rev. Earth Planet Sci.28, 509–537, 2000.

    Article  Google Scholar 

  7. Gibbons, S. J. and D. Gubbins, Convection in the Earth’s core driven by lateral variations in the core-mantle boundary heat flux, Geophys. J. Int., 142, 631–642, 2000.

    Article  Google Scholar 

  8. Humayun, M., L. Qin, and M. D. Norman, Geochemical evidence for excess iron in the mantle beneath Hawaii, Science, 306, 91–94, 2004.

    Article  Google Scholar 

  9. Kanda, R. V. and D. J. Stevenson, A suction mechanism for iron entrainment from the outer core into the lower mantle, EOS Trans AGU, 85, Fall Meet. Suppl., MR43A-0880

  10. Karato, S., Seismic anisotropy in the deep mantle, boundary layers and the geometry of mantle, Pure and Applied. Geophys., 151, 565–587, 1998.

    Article  Google Scholar 

  11. Kellogg, L. H., B. H. Hager, and R. D. van der Hilst, Compositional stratification in the deep mantle, Science, 283, 1881–1884, 1999.

    Article  Google Scholar 

  12. Koenders, M. A. and N. Petford, Quantitative analysis and scaling of sheared granitic magmas, Geophys. Res. Lett., 27, 1231–4, 2000.

    Article  Google Scholar 

  13. Lay, T., E. J. Garnero, and Q. Williams, Partial melting in a thermochemical boundary layer at the base of the mantle, Phys. Earth. Planet. Interior, 146, 441–467, 2004.

    Article  Google Scholar 

  14. Loper, D. E. and T. Lay, The core-mantle boundary region, J. Geophys. Res., 100, 6397–6420, 1995.

    Article  Google Scholar 

  15. Manga, M. and R. Jeanloz, Implications of a metal-bearing chemical boundary layer in D” for mantle dynamics, Geophys. Res. Lett., 23, 3091–3094, 1996.

    Article  Google Scholar 

  16. Mao, W., G. Shen, V. Prakapenka, Y. Meng, A. Campbell, D. Heinz, J. Shu, R. Hemley, and H. K. Mao, Ferromagnesian postperovskite silicates in the D” layer of the earth, Proc. Natl. Acad. Sci., 101, 15867–15869, 2004.

    Article  Google Scholar 

  17. McKenzie, D., The generation and compaction of partially molten rock, J. Petrol., 25, 713–765, 1984.

    Article  Google Scholar 

  18. McNamara, A. K., P. E. van Keken, and S. Karato, Development of anisotropic structure in the Earth’s lower mantle by solid-state convection, Nature, 416, 310–314, 2002.

    Article  Google Scholar 

  19. Mitrovica, J. X. and A. M. Forte, A new inference of mantle viscosity based upon joint inversion of convection and glacial isostatic adjustment data, Earth Planet. Sci. Lett., 225, 177–189, 2004.

    Article  Google Scholar 

  20. Murakami, M., K. Hiorse, K. Kawamura, N. Sata, and Y. Ohishi, Postperovskite phase transition in MgSiO3, Science, 304, 855–858, 2004.

    Article  Google Scholar 

  21. Oganov, A. R. and S. Ono, Theoretical and experimental evidence for a post-perovskite phase of MgSiO3 in Earth’s D” layer, Nature, 430, 445–448, 2004.

    Article  Google Scholar 

  22. Olson, P., Thermal interaction of the core and mantle, in Earth’s Core and Lower Mantle, edited by C. A. Jones, A. M. Soward, and K. Zhang, pp. 1–29, Taylor and Francis, London, 2003.

    Google Scholar 

  23. Petford, N. and M. A. Koenders, Shear-induced pressure changes and seepage phenomena in a deforming porous layer-I, Geophys. J. Int.155, 857–869, 2003.

    Article  Google Scholar 

  24. Poirier, Core-infiltrated mantle and the nature of the D” layer, J. Geomag. Geoelectr., 45, 1221–1227, 1995.

    Article  Google Scholar 

  25. Reynolds, O., On the dilatancy of media composed of rigid particles in contact, Phil. Mag., 20, 469–481, 1885.

    Article  Google Scholar 

  26. Rowe, P. W., The stress dilatancy of media composed of rigid particles in contact, with experimental illustrations. Proc. R. Soc. London, 269, 500–527, 1962.

    Article  Google Scholar 

  27. Ringwood, A. E., On the chemical evolution and densities of the planets, Geochimica et Cosmochimica Acta, 15, 257–283, 1959.

    Article  Google Scholar 

  28. Rushmer, T., W. G. Minarik, and G. I. Taylor, Physical processes of core formation, in Origin of the Earth and Moon, edited by K. Righter and R. Canup, pp. 227–245, Lunar Planetary Institute and University of Arizona Publishers, 2000.

    Google Scholar 

  29. Rushmer, T., N. Petford, and H. Humayun, Shear-induced segregation of Fe-liquid in planetesimals: coupling core forming compositions with transport phenomena, Lunar and Planetary ScienceXXXV1, 1320, Huston, 2005.

    Google Scholar 

  30. Schersten, A., T. Elliott, C. Hawkesworth, and M. Norman, Tungsten isotope evidence that mantle plumes contain no contribution from the Earth’s core, Nature, 427, 234–237, 2004.

    Article  Google Scholar 

  31. Stackhouse, S., J. P. Brodholt, J. Wookey, J-M. Kendall, and D. Price, The effect of temperature on the seismic anisotropy of the perovskite and post-perovskite polymorphs of MgSiO3, Earth Planet. Sci. Lett., 230, 1–10, 2005.

    Article  Google Scholar 

  32. Stevenson, D., Material transfer across the core-mantle boundary, Geophys. Res. Abstracts, 5, 03290, 2003.

    Google Scholar 

  33. Terasaki, H., D. J. Frost, D. C. Rubie, and F. Langenhorst, The effect of oxygen and sulphur on the dihedral angle between Fe-O-S melt and silicate minerals at high presure: Implications for Martian core formation, Earth Planet. Sci. Lett., 2005 (in press).

    Google Scholar 

  34. Terzaghi, K., Theoretical Soil Mechanics, John Wiley and Sons, New York, 528 pp., 1943.

    Google Scholar 

  35. Tsuchiya, T., J. Tsuchiya, K. Umemoto, and R. M. Wentzcovitch, Phase transition in MgSiO3 perovskite in the Earth’s lower mantle, Earth Planet. Sci. Lett., 224, 241–248, 2

    Article  Google Scholar 

  36. Turcotte, D. L. and G. Schubert, Geodynamics: Applications of Continuum Physics to Geological Problems (2nd Edition), Cambridge University Press, 456 pp., 2002.

    Google Scholar 

  37. Vasilyev, O. V., Y. Y. Podladchikov, and D. A. Yuen, Modeling of compaction driven flow in poro-viscoelastic medium using adaptive wavelet collocation method, Geophys. Res. Lett., 25, 3239–3243, 1998.

    Article  Google Scholar 

  38. Walter, M. J., A. Kubo, T. Yoshino, J. Brodholt, K. T. Koga, and Y. Ohishi, Phase relations and equation-of-state of aluminous Mg-silicate perovskite and implications for Earth’s lower mantle, Earth Planet Sci. Lett., 222, 501–516, 2004.

    Article  Google Scholar 

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Correspondence to Nick Petford.

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Petford, N., Yuen, D., Rushmer, T. et al. Shear-induced material transfer across the core-mantle boundary aided by the post-perovskite phase transition. Earth Planet Sp 57, 459–464 (2005). https://doi.org/10.1186/BF03351834

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Key words

  • Post-perovskite
  • dilatancy
  • D”
  • core metal transport
  • strain rate
  • deformation