A general feature of both isochemical and thermochemical studies of mantle convection is that horizontal plume velocities tend to be smaller than typical convective velocities, however, it is not clear which system leads to a greater fixity of mantle plumes. We perform twoand three-dimensional numerical calculations and compare both thermochemical and isochemical cases with similar convective v...

Seismological detections of complex structures in the lowermost mantle boundary layer (the D′′ region) motivate a conceptual model of a compositionally stratified thermo-chemical boundary layer (TCBL) within which lateral temperature variations (sustained by large-scale mid-mantle flow) cause variations of partial melt fraction. Partial melt fractions of from 0 to 30% in the TCBL occur due to t...

The Earth’s long-wavelength geoid anomalies have long been used to constrain the dynamics and viscosity structure of the mantle in an isochemical, whole mantle convection model. However, there is strong evidence that the seismically observed large low shear velocity provinces (LLSVPs) in the lower mantle underneath the Pacific and Africa are chemically distinct and likely denser than the ambien...

The core-mantle boundary (CMB) sepa­ rates dynamic systems with remarkable con­ trasts in composition and material properties (Table 1), comparable in magnitude to varia­ tions in properties across the surface of the solid Earth. A natural consequence of this pronounced stratification is the development of thermal and chemical boundary layers ad­ jacent to these interfaces, which thereby con­ s...

Temperature gradients in a low-shear-velocity province in the lowermost mantle (D'' region) beneath the central Pacific Ocean were inferred from the observation of a rapid S-wave velocity increase overlying a rapid decrease. These paired seismic discontinuities are attributed to a phase change from perovskite to post-perovskite and then back to perovskite as the temperature increases with depth...

Calculations of mantle convection generally use constant rates of internal heating and time-invariant core-mantle boundary temperature. In contrast, parameterized convection calculations, sometimes called thermal history calculations, allow these properties to vary with time but only provide a single average temperature for the entire mantle. Here I consider three-dimensional spherical convecti...

Where ρ0, α0, ∆T , η, κ are dimensional reference values of density of the background mantle, thermal expansivity, temperature difference between core-mantle boundary and surface, reference viscosity at temperature T = 0.5 (non-dimensional), and thermal diffusivity, respectively. g and h are dimensional gravitational acceleration and thickness of mantle, respectively. 1 Chemical complexity of h...

The role of decoupling in the low-velocity zone is crucial for understanding plate tectonics and mantle convection. Mantle convection models fail to integrate plate kinematics and thermodynamics of the mantle. In a first gross estimate, we computed at about 306 km/yr the volume of the plates lost along subduction zones. Mass balance predicts that slabs are compensated by broad passive upwelling...

[1] We calculate viscoelastic dissipation in the Moon using a rheological (extended Burgers) model based on laboratory deformation of melt-free polycrystalline olivine. Lunar temperature structures are calculated assuming steady state conduction with variable internal heat production and core heat flux. Successful models can reproduce the dissipation factor (Q) measured at both tidal and seismi...