Abstract Mosonik, a 3.25 Ma extensively dissected stratovolcano located in the North Tanzanian Divergence of East African Rift, consists predominantly phonolite and three types phonolitic nephelinite distinguished by presence or absence amphibole garnet antecrysts differing populations complexly zoned antecrystal phenocrystal pyroxenes. The antecryst–phenocryst assemblage is typical hybrid lava...

Numerical models of whole-mantle convection demonstrate that degassing of the mantle is an inefficient process, resulting in ca. 50% of the (40)Ar being degassed from the mantle system. In this sense the numerical simulations are consistent with the (40)Ar mass balance between the atmosphere and mantle reservoir. These models, however, are unable to preserve the large-scale heterogeneity predic...

[1] Through the assimilation of present-day mantle seismic structure, adjoint methods can be used to constrain the structure of the mantle at earlier times, i.e., mantle initial conditions. However, the application to geophysical problems is restricted through both the high computational expense from repeated iteration between forward and adjoint models and the need to know mantle properties (s...

We present a simple model of 3He and 4He transport in the mantle using the appropriate rates of mass and species transfer and 4He production. Previous workers have shown the presence of excess 3He in hotspots such as Hawaii and Iceland and inferred that these hotspots tap a source with a higher 3He/aHe ratio than the source region of mid-ocean ridge basalts (MORB). Hotspot ocean islands probabl...

sciencemag.org SCIENCE is a long-standing question in geology. Sarafian et al. present a clever set of experiments to determine the impact of small amounts of water on the melting temperature of mantle rock (see the Perspective by Asimow). This allowed them to reinterpret geophysical observations of melting in the mantle and revise estimates of mantle temperature upward. A hotter mantle has a m...

In the accretion process of planetesimals, there could be a lot of bodies with heterogeneous internal structures by pressure sintering, melting and gravity differentiation. They might have a core-mantle structure such as silicate core-porous silicate mantle or metal core-rock mantle. Therefore, we should consider a collisional phenomenon not only of a homogenous body but also of a core-mantle b...

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...