Dependence of diffusive radiative transfer on grain-size, temperature, and Fe-content: Implications for mantle processes

Hofmeister, Anne M.

doi:10.1016/j.jog.2005.06.001

Cited by 72 publications

(62 citation statements)

References 51 publications

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“…Radiative thermal conductivity increases rapidly with increasing temperature, and becomes significant at high temperatures (40,41). On the other hand, the effect of radiative heat transfer is diminished with the reduction of grain size; it is also controlled by the iron concentration of the minerals (42). Optical absorption measurements at high pressure have been used to infer the radiative thermal conductivity of lower-mantle minerals (43)(44)(45)(46).…”

Section: Discussionmentioning

confidence: 99%

Lattice thermal conductivity of MgO at conditions of Earth’s interior

Tang

Dong

2010

Proc. Natl. Acad. Sci. U.S.A.

142

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Thermal conductivity of the Earth's lower mantle greatly impacts the mantle convection style and affects the heat conduction from the core to the mantle. Direct laboratory measurement of thermal conductivity of mantle minerals remains a technical challenge at the pressure-temperature (P-T) conditions relevant to the lower mantle, and previously estimated values are extrapolated from low P-T data based on simple empirical thermal transport models. By using a numerical technique that combines first-principles electronic structure theory and Peierls-Boltzmann transport theory, we predict the lattice thermal conductivity of MgO, previously used to estimate the thermal conductivity in the Earth, at conditions from ambient to the core-mantle boundary (CMB). We show that our first-principles technique provides a realistic model for the P-T dependence of lattice thermal conductivity of MgO at conditions from ambient to the CMB, and we propose thermal conductivity profiles of MgO in the lower mantle based on geotherm models. The calculated conductivity increases from 15 -20 W∕K-m at the 670 km seismic discontinuity to 40 -50 W∕K-m at the CMB. This large depth variation in calculated thermal conductivity should be included in models of mantle convection, which has been traditionally studied based on the assumption of constant conductivity.first-principles | phonon transport theory | phonon lifetime | high pressure | Lower Mantle T hermal conductivity (κ) is one of the most important mineral properties in determining the heat budget of the Earth. Heat in the Earth's interior is transferred by convection in the mantle and core and regulated by conduction at thermal boundary layers. As defined by Fourier's law of heat conduction J Q ¼ −κ · ∇T, determines the conducting heat flow density (J Q ) in the presence of a temperature gradient ∇T. κ also appears in the Rayleigh number, which measures the convective vigor of a system. Thus, the thermal conductivity of the lower mantle affects the structure, thickness, and dynamics of the CMB (1, 2), the style and structure of mantle convection (3-5), and the amount of heat conducted from the core to the mantle (6) that in turn influences the generation of the Earth's magnetic field (7).Despite its importance, thermal conductivity remains as one of the least constrained physical properties of minerals, especially at lower-mantle pressures (P) and temperatures (T) and approximately 1,900-4,000 K (9-12). Experimental data at deep mantle conditions are scarce due to the technical difficulty of measuring thermal conductivity at these extremes. Thermal conductivity of lower-mantle minerals is often estimated either by extrapolating data from lower P-T conditions and/or employing theoretical models with parameters fitted with lower P-T data (1, 13). However, direct extrapolation to deep mantle conditions can be unreliable beyond the P-Trange of the measurements, and empirical models are often based on untested assumptions. For example, the sound velocities are used to approximate phonon vel...

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Section: Discussionmentioning

confidence: 99%

Lattice thermal conductivity of MgO at conditions of Earth’s interior

Tang

Dong

2010

Proc. Natl. Acad. Sci. U.S.A.

142

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“…However, radiative transfer of heat in the deep mantle is still a matter of controversy. It should be important or even dominant in olivine and perovskite (Hofmeister 1999(Hofmeister , 2005Badro, 2004;Gibert et al, 2005) as well as in postperovskite (Mao et al, 2005) but a decrease of radiative heat transfer with increase of pressure was observed for magnesiowüstite (Goncharov et al, 2006). Stabilization of superplumes enables forward studies of their properties, such as the adiabaticity of the superplume mode of heat transfer (Matyska and Yuen, 2001).…”

Section: Discussionmentioning

confidence: 99%

“…Other effects, not considered here, but which are nonetheless very important, are nonNewtonian rheology (e.g. Larsen and Yuen, 1997), grain-size dependent rheology (Solomatov, 1996(Solomatov, , 2001Korenaga, 2005) and grain-size dependent thermal conductivity (Hofmeister, 2005).…”

Section: Introductionmentioning

confidence: 99%

Lower-mantle material properties and convection models of multiscale plumes

Matyska

Yuen²

2007

Special Paper 430: Plates, Plumes and Planetary Processes

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We present the results of numerical mantle convection models demonstrating that dynamical effects induced by variable mantle viscosity, depth-dependent thermal expansivity, radiative thermal conductivity at the base of the mantle, the spinel to perovskite phase change and the perovskite to post-perovskite phase transition in the deep mantle can result in multiscale mantle plumes: stable lower-mantle superplumes are followed by groups of small upper-mantle plumes. Both radiative thermal conductivity at the base of the lower-mantle and a strongly decreasing thermal expansivity of perovskite in the lower-mantle can help to induce partially layered convection with intense shear heating under the transition zone, which creates a low viscosity zone and allow for the production of secondary mantle plumes emanating from this zone. Large-scale upwellings in the lower-mantle, which are induced mainly by both the style of lower-mantle viscosity stratification and decrease of thermal expansivity, control position of central upper-mantle plumes of each group as well as the upper-mantle plume-plume interactions.

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“…Recent work (e.g. Hofmeister, 2005Hofmeister, , 2006, has shown that the temperature dependencies are more complicated than previously thought, with strong ramifications for large scale (superplume) initiation in the lower mantle. Radiative, diffusive transfer inside the Earth is governed by two factors: the mean free path traveled by photons, and the photon flux.…”

Section: Macroscale Processes: Thermal-chemical (Super)plumes With Ramentioning

confidence: 99%

“…However, disruption and infiltration of the sediment pile by hotter upwelling liquid might act to pump heat locally into the lower mantle. Hofmeister (2005) has suggested that the thermal conductivity of lower-mantle minerals should decrease with increasing Fe content. With respect to the scale hierarchy of processes outlined earlier, this could give rise to an interesting non-local effect in which Fe drawn into the source region of a mantle plume developing at the CMB would selectively heat up the interior.…”

Section: Deformation Of Silicate (Ppv) Sediments Below the Cmbmentioning

confidence: 99%

Deformation-induced mechanical instabilities at the core-mantle boundary

Petford

Rushmer

Yuen

2007

Geophysical Monograph Series

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Our understanding of the core-mantle boundary (CMB) region has improved significantly over the past several years due, in part, to the discovery of the postperovskite phase. Sesimic data suggest that the CMB region is highly heterogeneous, possibly reflecting chemical and physical interaction between outer core material and the lowermost mantle. In this contribution we present the results of a new mechanism of mass transfer across the CMB and comment on possible repercussions that include the initiation of deep, siderophile-enriched mantle plumes. We view the nature of core-mantle interaction, and the geodynamic and geochemical ramifications, as multiscale processes, both spatially and temporally. Three lengthscales are defined. On the microscale (1-50 km), we describe the effect of loading and subsequent shearing of the CMB region and show how this may drive local flow of outer core fluid upwards into D″. We propose that larger scale processes operating on a mesoscale (50-300 km) and macroscale regimes (> 300 km) are linked to the microscale, and suggest ways in which these processes may impact on global mantle dynamics.

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Dependence of diffusive radiative transfer on grain-size, temperature, and Fe-content: Implications for mantle processes

Cited by 72 publications

References 51 publications

Lattice thermal conductivity of MgO at conditions of Earth’s interior

Lattice thermal conductivity of MgO at conditions of Earth’s interior

Lower-mantle material properties and convection models of multiscale plumes

Deformation-induced mechanical instabilities at the core-mantle boundary

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