Three-dimensional numerical simulations of crustal deformation and subcontinental mantle convection

https://doi.org/10.1016/S0012-821X(97)00093-9Get rights and content

Abstract

3-D simulations of mantle convection allowing for continental crust are explored to study the effects of crustal thickening on lithosphere stability and of continents on large-scale mantle flow. Simulations begin with a crustal layer within the upper thermal boundary layer of a mantle convection roll in a 1 × 1 × 1 Cartesian domain. Convective stresses cause crust to thicken above a sheet-like mantle downwelling. For mild convective vigor an initial crustal thickness variation is required to induce 3-D lithospheric instability below the zone of crustal convergence. The amplitude of the required variation decreases with increasing convective vigor. Morphologically, instability is manifest in formation of drip-like thermals that exist within the large-scale roll associated with initial crustal thickening. A strong surface signature of the drips is their ability to cause deviations from local Airy compensation of topography. After the initial thickening phase, the crustal accumulation that forms serves as a model analog to a continent. Its presence leads to mantle flow patterns distinctly different from the steady-state roll that results in its absence. Large lateral thermal gradients are generated at its edge allowing this region to be the initiation site for continued small-scale thermal instabilities. Eventually these instabilities induce a restructuring of large-scale mantle flow, with the roll pattern being replaced by a square cell. Although preliminary and idealized, the simulations do show the fluid dynamical plausibility behind the idea that significant mantle variations can be generated along the strike of a largely 2-D mountain chain by the formation of the chain itself. The ability of a model continent to cause a change in fundamental convective planform also suggests that the effects of continental crust on mantle convection may be low-order despite the seemingly trivial volume of crust relative to mantle.

References (37)

  • CliffordT.N.

    African structure and convection

    Trans. Leeds Geol. Assoc.

    (1968)
  • McKenzieD. et al.

    Speculations on the thermal and tectonic history of the Earth

    Geophys. J. R. Astron. Soc.

    (1975)
  • EthridgeM.A. et al.

    Orogenesis and tectonic process in the early to middle Proterozoic of Northern Australia

  • ElderJ.W.

    The evolution of the African thermal sublayer

    Trans. Leeds Geol. Assoc.

    (1968)
  • MuellerSt.

    Deep-reaching geodynamic processes in the Alps

  • JonesE.D. et al.

    Missing roots and mantle “drips”: Regional Pn and teleseismic arrival times in the southern Sierra Nevada and vicinity, California

    J. Geophys. Res.

    (1994)
  • HumphreysE.D. et al.

    Tomographic image of the southern California mantle

    J. Geophys. Res.

    (1990)
  • SeberD. et al.

    Geophysical evidence for lithospheric delamination beneath the Alboran Sea and Rif-Betic mountains

    Nature

    (1996)
  • Cited by (21)

    • Supercontinents, mantle dynamics and plate tectonics: A perspective based on conceptual vs. numerical models

      2011, Earth-Science Reviews
      Citation Excerpt :

      Such a study can also test whether the geologically suggested episodic emergence of supercontinents is realized in the numerical model. The thermal effect of accumulation of continental crust with compositionally buoyant materials on mantle convection has been previously evaluated in a series of papers (Lenardic and Kaula, 1994, 1995, 1996; Lenardic, 1997; Moresi and Lenardic, 1997; Lenardic, 1998; Moresi and Lenardic, 1999). Convective overturn of the mantle causes chemically light crust to thicken above the mantle downwelling and surface heat flux above the thick crust is lower than that above the mantle (Lenardic and Kaula, 1995).

    • Preliminary three-dimensional model of mantle convection with deformable, mobile continental lithosphere

      2010, Earth and Planetary Science Letters
      Citation Excerpt :

      The mechanism of crustal production and growth should be incorporated in a future numerical model so as to confirm this geologically suggested episodic emergence of supercontinents. The thermal effect of accumulations of continental crust with compositionally buoyant materials on mantle convection is previously published in a series of papers (Lenardic, 1997; Lenardic, 1998; Lenardic and Kaula, 1995; Lenardic and Kaula, 1996; Moresi and Lenardic, 1999; Moresi and Lenardic, 1997). Walzer and Hendel (2008) have recently performed simulations of 3D spherical mantle convection with the growth of a continent by considering the chemical differentiation and redistribution of incompatible elements.

    • The combined effects of continents and the 660 km-depth endothermic phase boundary on the thermal regime in the mantle

      2009, Physics of the Earth and Planetary Interiors
      Citation Excerpt :

      Being less dense and therefore, more buoyant than the mantle, continents do not participate in mantle overturn. Both numerical- and laboratory-based models have been created to investigate the dynamic interaction between the continental lithosphere and the mantle (Gurnis, 1988; Zhong and Gurnis, 1993; Guillou and Jaupart, 1995; Lowman and Jarvis, 1995, 1996; Lenardic and Kaula, 1995, 1996; Lenardic, 1997, 1998; Lenardic et al., 2005; Moresi and Lenardic, 1997; Grigné and Labrosse, 2001; Grigné et al., 2005, 2007a,b). Lenardic and Moresi (2001, 2003) investigated the variation of the surface heat flow as a function of the thickness and the lateral extent of the thermally coupled continents, and derived a parameterized model based on their numerical model results.

    • Intraplate tectonics: Feedback between radioactive thermal weakening and crustal deformation driven by mantle lithosphere instabilities

      2004, Earth and Planetary Science Letters
      Citation Excerpt :

      The results similarly show that time-varying over-compensated topography can develop under the influence of sub-lithospheric loading, but the analyses impose a constant mantle buoyancy load and consequently neglect the influence of time-dependent convection in the underlying mantle. Three-dimensional isoviscous simulations of time-dependent mantle convection that include a buoyant overlying crust demonstrate variable crustal accumulation and thickening above regions of downwelling mantle flow [17,18]. The resulting high positive topography is not in (Airy) isostatic equilibrium, as the crustal thickening is dynamically supported by the time-varying mantle fluid flow.

    View all citing articles on Scopus
    *

    Present address: CSIRO Exploration & Mining, P.O. Box 437, Nedlands 6009, Western Australia. Tel.: +61 8 9389 8421. Fax: +61 8 0389 1906.

    View full text