On the Scales of Dynamic Topography in Whole‐Mantle Convection Models

Arnould, Maëlis; Coltice, Nicolas; Flament, Nicolas; Seigneur, V.; Müller, R. Dietmar

doi:10.1029/2018gc007516

Cited by 29 publications

(29 citation statements)

References 76 publications

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“…While it is still a question whether plate-like velocities can be modelled with this approach, recent advances using continental rafts suggest Earth-like convective vigor may be in reach (e.g., Coltice et al 2013;Arnould et al 2018;Rolf et al 2018).…”

Section: Discussionmentioning

confidence: 99%

Subducted oceanic crust as the origin of seismically slow lower-mantle structures

Jones¹,

Maguire²,

Keken³

et al. 2020

Preprint

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Mantle tomography reveals the existence of two large low shear velocity provinces (LLSVPs) at the base of the mantle. We examine here the hypothesis that they are piles of oceanic crust that have steadily accumulated and warmed over billions of years. We use existing global geodynamic models in which dense oceanic crust forms at divergent plate boundaries and subducts at convergent ones. The model suite covers the predicted density range for oceanic crust over lower mantle conditions. To meaningfully compare our geodynamic models to tomographic structures we convert them into models of seismic wavespeed and explicitly account for the limited resolving power of tomography. Our results demonstrate that long-term recycling of dense oceanic crust naturally leads to the formation of thermochemical piles with seismic characteristics similar to the LLSVPs. The extent to which oceanic crust contributes to the LLSVPs depends upon its density in the lower mantle for which accurate data is lacking. We find that the LLSVPs are not composed solely of oceanic crust. Rather, they are basalt rich at their base (bottom 100--200~km) and grade into peridotite toward their sides and top with the strength of their seismic signature arising from the dominant role of temperature. We conclude that recycling of oceanic crust, if sufficiently dense, has a strong influence on the thermal and chemical evolution of Earth's mantle.

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Section: Discussionmentioning

confidence: 99%

Subducted oceanic crust as the origin of seismically slow lower-mantle structures

Jones¹,

Maguire²,

Keken³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…An interesting alternative is the use of the "yield-stress" rheology (e.g., Tackley 2000) which has been demonstrated to lead to plate-like behavior without the requirement of prescribing the geometry of the plates. While it is still a question whether plate-like velocities can be modeled with this approach, recent advances using continental rafts suggest Earth-like convective vigor may be in reach (e.g., Arnould et al 2018;Coltice et al 2013;and Rolf et al 2018).…”

Section: Discussionmentioning

confidence: 99%

Subducted oceanic crust as the origin of seismically slow lower-mantle structures

Jones

Maguire

Keken

et al. 2020

Prog Earth Planet Sci

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Mantle tomography reveals the existence of two large low-shear-velocity provinces (LLSVPs) at the base of the mantle. We examine here the hypothesis that they are piles of oceanic crust that have steadily accumulated and warmed over billions of years. We use existing global geodynamic models in which dense oceanic crust forms at divergent plate boundaries and subducts at convergent ones. The model suite covers the predicted density range for oceanic crust over lower mantle conditions. To meaningfully compare our geodynamic models to tomographic structures, we convert them into models of seismic wavespeed and explicitly account for the limited resolving power of tomography. Our results demonstrate that long-term recycling of dense oceanic crust naturally leads to the formation of thermochemical piles with seismic characteristics similar to the LLSVPs. The extent to which oceanic crust contributes to the LLSVPs depends upon its density in the lower mantle for which accurate data is lacking. We find that the LLSVPs are not composed solely of oceanic crust. Rather, they are basalt rich at their base (bottom 100-200 km) and grade into peridotite toward their sides and top with the strength of their seismic signature arising from the dominant role of temperature. We conclude that recycling of oceanic crust, if sufficiently dense, has a strong influence on the thermal and chemical evolution of Earth's mantle.

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“…We solve the equations of mass, momentum and energy conservation under the Boussinesq approximation:where v is velocity, p is pressure, η is viscosity, T is temperature and C is composition. H is the mantle internal heat production rate, α is a depth-dependent thermal expansivity coefficient set as in Arnould et al 2018 56 , B is the chemical buoyancy ratio and e r is the radial unit vector. The Rayleigh number of the system is:where α 0 is the surface thermal expansivity, D the mantle’s thickness, g the gravitational acceleration, Δ T the temperature gradient across the mantle, ρ 0 the reference density, η 0 the reference viscosity and κ the reference thermal diffusivity.…”

Section: Methodsmentioning

confidence: 99%

Northward drift of the Azores plume in the Earth’s mantle

et al. 2019

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Mantle plume fixity has long been a cornerstone assumption to reconstruct past tectonic plate motions. However, precise geochronological and paleomagnetic data along Pacific continuous hotspot tracks have revealed substantial drift of the Hawaiian plume. The question remains for evidence of drift for other mantle plumes. Here, we use plume-derived basalts from the Mid-Atlantic ridge to confirm that the upper-mantle thermal anomaly associated with the Azores plume is asymmetric, spreading over ~2,000 km southwards and ~600 km northwards. Using for the first time a 3D-spherical mantle convection where plumes, ridges and plates interact in a fully dynamic way, we suggest that the extent, shape and asymmetry of this anomaly is a consequence of the Azores plume moving northwards by 1–2 cm/yr during the past 85 Ma, independently from other Atlantic plumes. Our findings suggest redefining the Azores hotspot track and open the way for identifying how plumes drift within the mantle.

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On the Scales of Dynamic Topography in Whole‐Mantle Convection Models

Cited by 29 publications

References 76 publications

Subducted oceanic crust as the origin of seismically slow lower-mantle structures

Subducted oceanic crust as the origin of seismically slow lower-mantle structures

Subducted oceanic crust as the origin of seismically slow lower-mantle structures

Northward drift of the Azores plume in the Earth’s mantle

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