Stagnant slabs in the upper and lower mantle transition region

Fukao, Yoshio; Widiyantoro, Sri; Obayashi, Masayuki

doi:10.1029/1999rg000068

Cited by 603 publications

(460 citation statements)

References 151 publications

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“…Slabs could temporarily stack in the mid-mantle, and reach the bottom of the mantle in occasional avalanches (Tackley et al, 1994). There are indeed some indications from classical tomography that significant amounts of slabs are deflected in the top of the lower mantle, around 1000 km (Fukao et al, 2001). The variations of temperature and composition (mainly perovskite) observed by probabilistic tomography at the top of the lower mantle could also be due to deflected slabs.…”

Section: Discussionmentioning

confidence: 98%

Thermo-Chemical Structure of the Lower Mantle: Seismological Evidence and Consequences for Geodynamics

Deschamps

Trampert

Tackley

2007

Superplumes: Beyond Plate Tectonics

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We combine recent progress in seismic tomography and numerical modeling of thermochemical convection to infer robust features on mantle structure and dynamics. First, we separate the observed density anomalies into their thermal and compositional contributions. The tomographic maps of thermo-chemical variations were computed using a new approach that combines a careful equation of state modeling of the lower mantle, independent constraints on density from probabilistic tomography, and a full statistical treatment for uncertainties analyses. We then test models of thermo-chemical convection against these density components. We compute synthetic anomalies of thermal and compositional density from models of thermo-chemical convection calculated with the anelastic approximation. These synthetic distributions are filtered to make meaningful comparisons with the observed density anomalies. Our comparisons suggest that a stable layer (i.e., that no domes or piles are generated from it) of dense material with buoyancy ratio B ≥ 0.3 is unlikely to be present at the bottom of the mantle. Models of piles entrained upwards from a dense, but unstable layer with buoyancy ratio B ∼ 0.2, explain the observation significantly better, but discrepancies remain at the top of the lower mantle. These discrepancies could be linked to the deflection of slabs around 1000 km, or to the phase transformation at 670 km, not included yet in the thermo-chemical calculations.

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Section: Discussionmentioning

confidence: 98%

Thermo-Chemical Structure of the Lower Mantle: Seismological Evidence and Consequences for Geodynamics

Deschamps

Trampert

Tackley

2007

Superplumes: Beyond Plate Tectonics

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“…[3] Sinking of the lithosphere into the mantle is characterized by asymmetric subduction of one plate beneath another with slab dips of 30°to 90°, as constrained by seismicity to depths of 670 km [Isacks and Barazangi, 1977] and seismic tomography [Gudmundsson and Sambridge, 1998;Kárason and van der Hilst, 2001;Fukao et al, 2001]. The relationships between the present-day shape of slabs and slab buoyancy, surface plate motions, seismic coupling and history of subduction provide insight into the physical processes controlling the time evolution of slabs.…”

Section: Subduction Observablesmentioning

confidence: 99%

“…These models show that depending on (1) the magnitude of the viscosity jump or clapeyron slope for the phase changes, (2) the rate of trench migration, and (3) the strength of the slab, the slab can either cross unperturbed into the lower mantle, form temporary piles, or lie flat in the transition zone. All three of these slab morphologies are inferred from seismic tomography [e.g., Fukao et al, 2001;Kárason and van der Hilst, 2001].…”

Section: Subduction Modelsmentioning

confidence: 99%

Rheologic controls on slab dynamics

Billen

Hirth

2007

Geochem Geophys Geosyst

205

186

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[1] Several models have been proposed to relate slab geometry to parameters such as plate velocity or plate age. However, studies on the observed relationships between slab geometry and a wide range of subduction parameters show that there is not a simple global relationship between slab geometry and any one of these other subduction parameters for all subduction zones. Numerical and laboratory models of subduction provide a method to explore the relative importance of different physical processes in determining subduction dynamics. Employing 2-D numerical models with a viscosity structure constrained by laboratory experiments for the deformation of olivine, we show that the observed range in slab dip and the observed trends between slab dip and convergence velocity, subducting plate age, and subduction duration can be reproduced without trench motion (i.e., slab roll-back) for locations away from slab edges. Successful models include a stiff slab that is 100-1000 times more viscous than previous estimates from models of plate bending, the geoid, and global plate motions. We find that slab dip in the upper mantle depends primarily on slab strength and plate boundary coupling, with a small dependence on subducting plate age. Once the slab sinks into the lower mantle the primary processes controlling slab evolution are (1) the ability of the stiff slab to transmit stresses up dip, (2) resistance to slab descent into the higherviscosity lower mantle, and (3) subduction-induced flow in the mantle-wedge corner.

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“…Among the success stories of global tomography are the delineation of long-wavelength variations in elastic properties in Earth's mantle, which started in the early 1980s, and the detailed delineation, over the last decade or so, of trajectories of mantle convection [see reviews by, e.g., Dziewonski and Woodhouse, 1987;Woodhouse and Dziewonski, 1989;Masters, 1989;Romanowicz, 1991;Montagner, 1994;Masters and Shearer, 1995;Ritzwoller and Lavely, 1995;Dziewonski, 1996;Masters et al, 2000;Kárason and van der Hilst, 2000;Fukao et al, 2001;Romanowicz, 2003]. It is encouraging to see that increasingly consistent information on the spatial patterns of wave speed variations is emerging from tomographic studies that use different data and/or techniques.…”

Section: Introductionmentioning

confidence: 99%

Towards a quantitative interpretation of global seismic tomography

Trampert

Hilst

2005

Geophysical Monograph Series

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We review the success of seismic tomography in delineating spatial variations in the propagation speed of seismic waves on length scales from several hundreds to many thousands of kilometers. In most interpretations these wave speed variations are thought to reflect variations in temperature. Careful consideration of shear wave, bulk sound, and, most recently, density variations is, however, producing increasingly compelling evidence for chemical heterogeneity (that is, spatial variations in bulk major element composition) having a first-order effect on the lateral variations in mass density and elasticity of the mantle. This has profound consequences for our understanding of mantle dynamics and the thermochemical evolution of our planet. We argue that the quantitative integration of constraints from seismology, mineral physics, and geodynamics, which underlies the inference of thermochemical parameters, requires careful uncertainty analyses and should move away from emphasizing visually pleasing images and single, nonunique solutions.

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Stagnant slabs in the upper and lower mantle transition region

Cited by 603 publications

References 151 publications

Thermo-Chemical Structure of the Lower Mantle: Seismological Evidence and Consequences for Geodynamics

Thermo-Chemical Structure of the Lower Mantle: Seismological Evidence and Consequences for Geodynamics

Rheologic controls on slab dynamics

Towards a quantitative interpretation of global seismic tomography

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