Diamond is an evidence for carbon existing in the deep Earth. Some diamonds are considered to have originated at various depth ranges from the mantle transition zone to the lower mantle. These diamonds are expected to carry significant information about the deep Earth. Here, we determined the phase relations in the MgCO3-SiO2 system up to 152 GPa and 3,100 K using a double sided laser-heated di...

The deepest rocks known from within Earth are fragments of normal mantle ( approximately 400 km) and metamorphosed sediments ( approximately 350 km), both found exhumed in continental collision terranes. Here, we report fragments of a highly reduced deep mantle environment from at least 300 km, perhaps very much more, extracted from chromite of a Tibetan ophiolite. The sample consists, in part,...

We report the current status of our numerical simulation code named “ACuTEMan” for large-scale mantle convection problems on the Earth Simulator. The ACuTEMan code comes out from a newly-developed “ACuTE” algorithm, which solves the flow field of mantle convection in combination with the multigrid method. This algorithm iteratively solves the steady-state equations for conservation of mass and ...

The mantle of the Earth, and probably of other terrestrial planets as well, is heated from below and within. The heating mode of mantle convection is thus mixed heating, and it is also time dependent because the amount of heat-producing isotopes in the mantle is steadily decreasing by radioactive decay and because the basal heat flux originating in the cooling of the core can vary with time. Th...

The notion of self-regulating mantle convection, in which heat loss from the surface is constantly adjusted to follow internal radiogenic heat production, has been popular for the past six decades since Urey first advocated the idea. Thanks to its intuitive appeal, this notion has pervaded the solid earth sciences in various forms, but approach to a self-regulating state critically depends on t...

The Earth’s core is made up of a solid inner portion, encircled by a liquid metallic region [Fig. 1]. Surrounding this is a thick mantle made up of silicates and minor amounts of metal (perhaps reaching 1 wt%), and the outermost layer is the crust, made up of silicates (Figure 1). The mantle is not homogeneous – there are distinct regions of differing mineralogy and composition [2]. Understandi...

aving considered the Earth’s formation in the last chapter, let’s now use the tools of geochemistry we acquired in the first eight chapters to consider how the Earth works. The Earth, unlike many of its neighbors, has evolved over its long history and it remains geologically active. Four and a half billion years later, it is very different place than it was first formed. Certainly one of the ma...

The initial melting of mantle plumes produced unparalleled volumes of lava that formed large igneous provinces (LIPs). These events were sometimes so large that they triggered catastrophic mass extinctions and oceanic anoxic events. Global tomography and numerical models suggest that mantle plume occurrences are closely linked to the margins of the large low shear velocity provinces (LLSVPs) lo...

[1] Subduction zones are where sediments, oceanic crust, and mantle lithosphere return to and reequilibrate with Earth’s mantle. Subduction zones are interior expressions of Earth’s 55,000 km of convergent plate margins and are the geodynamic system that builds island arcs. Excess density of the mantle lithosphere in subduction zones provides most of the power needed to move the plates while in...

Editor: T.M. Harrison Non-arc basalts of Archean and Proterozoic age have model primary magmas that exhibit mantle potential temperatures TP that increase from 1350 °C at the present to a maximum of ∼1500–1600 °C at 2.5–3.0 Ga. The overall trend of these temperatures converges smoothly to that of the present-day MORB source, supporting the interpretation that the non-arc basalts formed by the m...