Large-scale tectonic processes introduce a range of crustal lithologies into the Earth's mantle. These lithologies have been implicated as sources of compositional heterogeneity in mantle-derived magmas. The model being explored here assumes the presence of widely dispersed fragments of residual eclogite (derived from recycled oceanic crust), stretched and stirred by convection in the mantle. H...

Carbonatites are mantle-derived, intraplate magmas that provide a means of documenting isotopic variations of the Earth's mantle through time. To investigate the secular Li isotopic evolution of the mantle and to test whether Li isotopes document systematic recycling of material processed at or near the Earth's surface into the mantle, we analyzed the Li isotopic compositions of carbonatites an...

[1] Although mantle slabs ultimately drive plate motions, the mechanism by which they do so remains unclear. A detached slab descending through the mantle will excite mantle flow that exerts shear tractions on the base of the surface plates. This ‘‘slab suction’’ force drives subducting and overriding plates symmetrically toward subduction zones. Alternatively, cold, strong slabs may effectivel...

A parameterized model of mantle convection that includes the effects of volatile exchange between the mantle and the surface reservoir and the softening of the mantle by the dissolved volatiles is used to study the thermal history of the Earth. It is assumed that the activation energy for temperature-dependent solid-state creep is a linear function of weight percent of volatiles. The mantle deg...

Receiver functions derived from body waves recorded in Iceland and on the Hawaiian Islands reveal a seismic velocity discontinuity at about 1050 km depth beneath the two regions of presumed mantle upwelling. The waveforms of the converted phases from the mid-mantle discontinuity indicate a velocity increase with depth. The lack of consistent scattering found in recent systematic searches for se...

The effect depth-dependent viscosity has on convective mixing and sampling (or degassing) of primitive mantle beneath ridges is explored in two-dimensional models. Higher relative viscosities in the deep mantle decrease convection velocities and strain rates and prolong the residence time of material in the deep mantle. If the average viscosity of the lower mantle is at least 100 times the visc...

Advances in our understanding of Earth's thermal evolution and the style of mantle convection rely on robust seismological constraints on lateral variations of density. The large-low-shear-wave velocity provinces (LLSVPs) atop the core-mantle boundary beneath Africa and the Pacific are the largest structures in the lower mantle, and hence severely affect the convective flow. Here, we show that ...

Recent seismological studies demonstrate the presence of strong deep-mantle elastic heterogeneity and anisotropy, consistent with a dynamic environment having chemical anomalies, phase changes, and partially molten material. The implications for deep-mantle plume genesis are discussed in the light of the seismological findings. Nearly antipodal large low–shear velocity provinces (LLSVPs) in the...

 The effects of seasons on lipid and fatty acid profiles of muscle types (mantle and arm) of Mediterranean octopuses (common octopus-Octopus vulgaris and musky octopus-Eledone moschata) were investigated. The results showed that lipid levels ranged from 0.75% to 1.60% in both muscle types of octopuses which were considered as lean. Lipid levels in mantle tissues of both octopus species were hig...