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Small-scale mineralogical heterogeneity from variations in phase assemblages in the transition zone and D″ layer predicted by convection modelling

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Abstract

Small-scale heterogeneity in the deep mantle is concentrated in the upper-mantle transition zone (TZ), in the depth range 410–660 km and also at the bottom 250 km D″ region. This encourages a more detailed investigation of the potential for seismic reflectivity imaging by modelling heterogeneous structures in mantle convection models including phase transitions of the TZ and D″ regions. We applied finite elements with variable spacing near the boundary layers in 2-D cylindrical geometry that allow for sufficient spatial resolution. We investigated several models including an extended Boussinesq (EBA) model, focused on the D″ region, and a compressible (ALA) model for the TZ region. The results for the D″ region show typical lens-shaped structures of post-perovskite (PPV) embedded in the perovskite (PV) background mantle, where the thickness of the lenses, at 200–400 km, strongly depends on the Clapeyron slope of the PV-PPV transition. A second phase transition (double crossing) occurs in case the core temperature is higher than the intercept temperature T i . Our phase-dependent rheology results in contrasting effective viscosity between PV and PPV. Our model results reveal a distinctly clear mechanical weakening of the PPV lenses with about an order of magnitude lower viscosity. The shear wave-speed distributions computed from our convection results are strongly correlated with the heterogeneous distribution of the mineral phase. Gradients in the seismic wave-speed that are the target of seismological reflectivity imaging are clearly revealed. The wave-speed results show a clear resolution of the top and bottom interfaces of the PPV lenses. Our ALA model for the TZ is based on a thermodynamical model for the magnesium end-member of an olivine-pyroxene mantle. The model predicts a much more complex distribution of mineral phases, compared to our D″ results, in agreement with the greater number of mineral phases involved in the olivine-pyroxene phase diagram for the P, T conditions of the transition zone. Near cold downwelling flows representing subducting lithospheric slabs, where the local geotherm can differ by up to 1 000 K from the horizontal average, and small-scale lateral variations in the mineral phases can occur.

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References Cited

  • Ammann, M. W., Brodholt, J. P., Wookey, J., et al., 2010. First-Principles Constraints on Diffusion in Lower-Mantle Minerals and a Weak D″ Layer. Nature, 465(7297): 462–465

    Article  Google Scholar 

  • Boehler, R., 2000. High-Pressure Experiments and the Phase Diagram of Lower Mantle and Core Materials. Reviews of Geophysics, 38(2): 221–245

    Article  Google Scholar 

  • Cadek, O. Fleitout, L., 2006. Effect of Lateral Viscosity Variations in the Core-Mantle Boundary Region on Predictions of the Long-Wavelength Geoid. Stud. Geophys. Geod., 50(2): 217–232

    Article  Google Scholar 

  • Cao, Q., Wang, P., van der Hilst, R. D., et al., 2010. Imaging the Upper Mantle Transition Zone with a Generalized Radon Transform of SS Precursors. Phys. Earth Planet. Inter., 180(1–2): 80–91

    Article  Google Scholar 

  • Catalli, K., Shim, S. H., Prakapenka, V., 2009. Thickness and Claeyron Slope of the Post-Perovskite Boundary. Nature, 462(7274): 782–785

    Article  Google Scholar 

  • Christensen, A. U. R., Yuen, D. A., 1985. Layered Convection Induced by Phase Transitions. J. Geophys. Res., 90:10291–10300

    Article  Google Scholar 

  • Connolly, J. A. D., 2005. Computation of Phase Equilibria by Linear Programming: A Tool for Geodynamic Modeling and Its Application to Subduction Zone Decarbonation. Earth Planet. Sci. Lett., 236(1–2): 524–541

    Article  Google Scholar 

  • Daessler, R., Yuen, D. A., 1993. The Effects of Phase Transition Kinetics on Subducting Slabs. Geophys. Res. Lett., 20(23): 2603–2606

    Article  Google Scholar 

  • de Hoop, M. V., Smith, H., Uhlmann, G., et al., 2009. Seismic Imaging with the Generalized Radon Transform: A Curvelet Transform Perspective. Inverse Problems, 25(2): 025005

    Article  Google Scholar 

  • Hernlund, J. W., Thomas, C., Tackley, P. J., 2005. A Doubling of the Post-Perovskite Phase Boundary and Structure of the Earth’s Lowermost Mantle. Nature, 434(7035): 882–886

    Article  Google Scholar 

  • Hunt, S. A., Weidner, D. J., Li, L., et al., 2009. Weakening of Calcium Iridate during Its Transformation from Perovskite to Post-Perovskite. Nature Geoscience, 2(11):794–797

    Article  Google Scholar 

  • Jacobs, M. H. G., de Jong, B. H. W. S., 2007. Placing Constraints on Phase Equilibria and Thermophysical Properties in the System MgO-SiO2 by a Thermodynamically Consistent Vibrational Method. Geochimica et Cosmochimica Acta, 71(14): 3630–3655

    Article  Google Scholar 

  • Jacobs, M. H. G., van den Berg, A. P., 2011. Complex Phase Distribution and Seismic Velocity Structure of the Transition Zone: Convection Model Predictions for a Magnesium-Endmember Olivine-Pyroxene Mantle. Phys. Earth Planet. Inter. (Accepted)

  • Jarvis, G. T., McKenzie, D. P., 1980. Convection in a Compressible Fluid with Infinite Prandtl Number. J. Fluid Mech., 96: 515–583

    Article  Google Scholar 

  • Karato, S. I., 2008. Deformation of Earth Materials: An Introduction to the Rheology of Solid Earth. Cambridge University Press, Cambridge

    Google Scholar 

  • Karato, S. I., 2010. The Influence of Anisotropic Diffusion on the High-Temperature Creep of a Polycrystalline Aggregate. Phys. Earth Planet. Inter., 183(3–4): 468–472

    Article  Google Scholar 

  • King, S. D., Lee, C., van Keken, P. E., et al., 2010. A Community Benchmark for 2-D Cartesian Compressible Convection in the Earth’s Mantle. Geophys. J. Int., 180(1): 73–87

    Article  Google Scholar 

  • Lay, T., Hernlund, J., Garnero, E. J., et al., 2006. A Post-Perovskite Lens and D″ Heat Flux beneath the Central Pacific. Science, 314(5803): 1272–1276

    Article  Google Scholar 

  • Murakami, M., Hirose, K., Kawamura, K., et al., 2004. Post-Perovskite Phase Transition in MgSiO3. Science, 304(5672): 855–858

    Article  Google Scholar 

  • Nakagawa, T., Tackley, P. J., 2010. Influence of Initial CMB Temperature and Other Parameters on the Thermal Evolution of Earth’s Core Resulting from Thermochemical Spherical Mantle Convection. Geochemistry, Geophysics, Geosystems, 11: Q06001

    Article  Google Scholar 

  • Schubert, G., Turcotte, D. L., Olson, P., 2001. Mantle Convection in the Earth and Planets. Cambridge University Press, Cambridge

    Book  Google Scholar 

  • Steinbach, V., Hansen, U., Ebel, A., 1989. Compressible Convection in the Earth’s Mantle: A Comparison of Different Approaches. Geophys. Res. Lett., 16: 633–636

    Article  Google Scholar 

  • Tosi, N., Cadek, O., Martinec, Z., et al., 2009. Is the Long-Wavelength Geoid Sensitive to the Presence of Post-Perovskite above the Core-Mantle Boundary? Geophys. Res. Lett., 36: L05303

    Article  Google Scholar 

  • Vacher, P., Spakman, W., Wortel, M. J. R., 1999. Numerical Tests on the Seismic Visibility of Metastable Minerals in Subduction Zones. Earth Planet. Sci. Lett., 170(3):335–349

    Article  Google Scholar 

  • van den Berg, A. P., van Keken, P. E., Yuen, D. A., 1993. The Effects of a Composite Non-Newtonian and Newtonian Rheology on Mantle Convection. Geophysical Journal International, 115(1): 62–78

    Article  Google Scholar 

  • van den Berg, A. P., de Hoop, M. V., Yuen, D. A., et al., 2010. Geodynamical Modeling and Multiscale Seismic Expression of Thermo-chemical Heterogeneity and Phase Transitions in the Lowermost Mantle. Phys. Earth Planet. Int., 180(3–4): 244–257

    Article  Google Scholar 

  • van der Hilst, R. D., de Hoop, M. V., Wang, P., et al., 2007. Seismostratigraphy and Thermal Structure of Earth’s Core-Mantle Boundary Region. Science, 315(5820):1813–1817

    Article  Google Scholar 

  • van Hunen, J., van den Berg, A. P., Vlaar, N. J., 2002. On the Role of Subducting Oceanic Plateaus in the Development of Shallow Flat Subduction. Tectonophysics, 352(3–4):317–33

    Article  Google Scholar 

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Correspondence to Arie P. van den Berg.

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This study was supported by the CMG Program of NSF, Senior Visiting Professorship by the Chinese Academy of Sciences, The Netherlands Research Center for Integrated Solid Earth Science (ISES 3.2.5), and the 216 through ISES Project ME-2.7.

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van den Berg, A.P., Yuen, D.A., Jacobs, M.H.G. et al. Small-scale mineralogical heterogeneity from variations in phase assemblages in the transition zone and D″ layer predicted by convection modelling. J. Earth Sci. 22, 160–168 (2011). https://doi.org/10.1007/s12583-011-0168-7

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  • DOI: https://doi.org/10.1007/s12583-011-0168-7

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