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Shear-induced material transfer across the core-mantle boundary aided by the post-perovskite phase transition
Earth, Planets and Space volume 57, pages459–464(2005)
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.
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.
Biot, M. A., General theory of three dimensional consolidation, J. Appl. Phys., 12, 155–164, 1941.
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.
Buffett, B. A., E. J. Garnero, and R. Jeanolz, Sediments at the top of the Earth’s core, Science, 290, 1338–1342, 2000.
Bruhn, D., N. Groebner, and D. L. Kohlstedt, An interconnected network of core-forming melts produced by shear deformation, Nature, 403, 883–886, 2000.
Garnero, E. J., Heterogeneities in the lowermost mantle, Annu. Rev. Earth Planet Sci.28, 509–537, 2000.
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.
Humayun, M., L. Qin, and M. D. Norman, Geochemical evidence for excess iron in the mantle beneath Hawaii, Science, 306, 91–94, 2004.
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
Karato, S., Seismic anisotropy in the deep mantle, boundary layers and the geometry of mantle, Pure and Applied. Geophys., 151, 565–587, 1998.
Kellogg, L. H., B. H. Hager, and R. D. van der Hilst, Compositional stratification in the deep mantle, Science, 283, 1881–1884, 1999.
Koenders, M. A. and N. Petford, Quantitative analysis and scaling of sheared granitic magmas, Geophys. Res. Lett., 27, 1231–4, 2000.
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.
Loper, D. E. and T. Lay, The core-mantle boundary region, J. Geophys. Res., 100, 6397–6420, 1995.
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.
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.
McKenzie, D., The generation and compaction of partially molten rock, J. Petrol., 25, 713–765, 1984.
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.
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.
Murakami, M., K. Hiorse, K. Kawamura, N. Sata, and Y. Ohishi, Postperovskite phase transition in MgSiO3, Science, 304, 855–858, 2004.
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.
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.
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.
Poirier, Core-infiltrated mantle and the nature of the D” layer, J. Geomag. Geoelectr., 45, 1221–1227, 1995.
Reynolds, O., On the dilatancy of media composed of rigid particles in contact, Phil. Mag., 20, 469–481, 1885.
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.
Ringwood, A. E., On the chemical evolution and densities of the planets, Geochimica et Cosmochimica Acta, 15, 257–283, 1959.
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.
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.
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.
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.
Stevenson, D., Material transfer across the core-mantle boundary, Geophys. Res. Abstracts, 5, 03290, 2003.
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).
Terzaghi, K., Theoretical Soil Mechanics, John Wiley and Sons, New York, 528 pp., 1943.
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
Turcotte, D. L. and G. Schubert, Geodynamics: Applications of Continuum Physics to Geological Problems (2nd Edition), Cambridge University Press, 456 pp., 2002.
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.
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.
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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
- core metal transport
- strain rate