Lower-mantle material properties and convection models of multiscale plumes

Matyska, Ctirad; Yuen, David A.

doi:10.1130/2007.2430(08)

Cited by 7 publications

(5 citation statements)

References 96 publications

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“…Aside from the phase transitions taking place in the 300-800 km depth interval, phase transformations at mid and lower mantle depths could also affect the Earth's internal dynamics. The post-perovskite transformation has a strongly positive Clapeyron slope, which destabilizes the chemically-dense material piling within the lower thermal boundary, slightly increases the heat flow and the interior mantle temperature, and increases the number and upwelling velocities of plumes (Matyska and Yuen, 2007;Tackley, 2004, 2005;Tackley et al, 2007;Yuen et al, 2007). However, because of the small density difference (1%), the destabilizing effect is relatively small despite the large Clapeyron slope, so that the post-perovskite transformation has likely less influence than other uncertainties in deep mantle parameters, such as the density of MORB (Tackley, 2012).…”

Section: Buoyancy and Thermal Effectsmentioning

confidence: 99%

The role of solid–solid phase transitions in mantle convection

Faccenda

Zilio

2017

Lithos

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Section: Buoyancy and Thermal Effectsmentioning

confidence: 99%

The role of solid–solid phase transitions in mantle convection

Faccenda

Zilio

2017

Lithos

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“…The dimensionless viscosity η depends on pressure (depth) and temperature as follows (e.g., Matyska and Yuen, 2007) …”

Section: Model Description Rheology and Materials Parametersmentioning

confidence: 99%

Influences of lower-mantle properties on the formation of asthenosphere in oceanic upper mantle

2011

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Asthenosphere is a venerable concept based on geological intuition of Reginald Daly nearly 100 years ago. There have been various explanations for the existence of the asthenosphere. The concept of a plume-fed asthenosphere has been around for a few years due to the ideas put forth by Yamamoto et al.. Using a two-dimensional Cartesian code based on finite-volume method, we have investigated the influences of lower-mantle physical properties on the formation of a low-viscosity zone in the oceanic upper mantle in regions close to a large mantle upwelling. The rheological law is Newtonian and depends on both temperature and depth. An extended-Boussinesq model is assumed for the energetics and the olivine to spinel, the spinel to perovskite and perovskite to post-perovskite (ppv) phase transitions are considered. We have compared the differences in the behavior of hot upwellings passing through the transition zone in the mid-mantle for a variety of models, starting with constant physical properties in the lower-mantle and culminating with complex models which have the post-perovskite phase transition and depth-dependent coefficient of thermal expansion and thermal conductivity. We found that the formation of the asthenosphere in the upper mantle in the vicinity of large upwellings is facilitated in models where both depth-dependent thermal expansivity and conductivity are included. Models with constant thermal expansivity and thermal conductivity do not produce a hot low-viscosity zone, resembling the asthenosphere. We have also studied the influences of a cylindrical model and found similar results as the Cartesian model with the important difference that upper-mantle temperatures were much cooler than the Cartesian model by about 600 to 700 K. Our findings argue for the potentially important role played by lower-mantle material properties on

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“…The background of the extended Boussinesq equations can be found described in Christensen and Yuen (1985) and more completely in Matyska and Yuen (2007). In the extended Boussinesq approximation the mantle compressibility in the continuity equation is neglected.…”

Section: Governing Equationsmentioning

confidence: 99%

The dynamical influences from physical properties in the lower mantle and post-perovskite phase transition

Yuen

Matyska

Čadek

et al. 2007

Geophysical Monograph Series

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The discovery of post-perovskite phase transition near the core-mantle boundary(CMB) has turned our heads to the potentially important role played by the increasing complexity of the physical properties in the lower-mantle models. In this study we have investigated the influences on lower mantle dynamics by the strongly depth-dependent coefficient of thermal expansion and radiative thermal conductivity together with the post-perovskite transition within the framework of isochemical models We have carried out the simulations in both 2-D and 3-D Cartesian geometries. First, we review the basic connection between the temperature profile and the Clapeyron slope, calling attention to the special relationship between the temperature intercept of the post-perovskite phase change and the temperature at the core-mantle boundary. Doublecrossing of the post-perovskite boundary takes place only, when the temperature of the CMB is greater than the temperature intercept of the phase change. We find that mantle plumes become multiscale in nature because of the combined effects exerted by variable mantle viscosity, strongly depth-dependent thermal expansivity, radiative thermal conductivity at the bottom of the mantle, the spinel to perovskite phase transition and the perovskite to post-perovskite phase change in the deep mantle. Both radiative thermal conductivity and strongly decreasing thermal expansivity in the lower mantle can help to induce partially layered convection with slabs stagnating in the transition zone. In our isochemical models a second low viscosity zone is created under the transition zone accompanied by intense shear heating. Secondary mantle plumes emerge from this region at the base of the transition zone. Large-scale upwellings in the lower mantle are induced mainly by both the style of lower-mantle stratification and the decrease in thermal expansivity. They control the location and the local dynamics of the upper-mantle plumes. In these models with variable thermal conductivity and viscosity, an increase in the temperature of the CMB causes a greater tendency for layered convection. From the same depthdependent thermal expansivity, we can deduce the 3-D density anomalies from the seismic velocity anomalies inferred from seismic tomographic inversion. Using these density distributions, we can calculate the viscous responses of the Earth due to these density anomalies for a given viscosity structure. We then focus on the lateral viscosity variations of the deep mantle on the solution of the inverse problem involving the inferences of the viscosity from the long-wavelength geoid. Our solution for the large-scale lateral viscosity structure in the lowermost mantle shows that the region underneath hot spots have significantly higher viscosity in the deep mantle than the region below subduction regions. Recent inferences from firstprinciples calculations and laboratory experiments on analogue post-perovskite material also surmise the rheology of post-perovskite would be dominated by dislocation mechanism and ...

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Lower-mantle material properties and convection models of multiscale plumes

Cited by 7 publications

References 96 publications

The role of solid–solid phase transitions in mantle convection

The role of solid–solid phase transitions in mantle convection

Influences of lower-mantle properties on the formation of asthenosphere in oceanic upper mantle

The dynamical influences from physical properties in the lower mantle and post-perovskite phase transition

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