Recycled oceanic crust, with or without sediment, is often invoked as a source component of continental and oceanic alkaline magmas to account for their trace-element and isotopic characteristics. Alternatively, these features have been attributed to sources containing veined, metasomatized lithosphere. In melting experiments on natural amphibole-rich veins at 1.5 gigapascals, we found that par...

Kimberlites from West Greenland have Hf–Nd isotope as well as major and trace element compositions that are similar to other Group I kimberlites, but that are distinctive in the spectrum of magmas sampled at Earth’s surface. The West Greenland kimberlites have eNdi that ranges from +1.6 to +3.1 and eHfi that ranges from 4.3 to +4.9. The samples exhibit ubiquitous negative DeHfi (deviation from ...

a r t i c l e i n f o Crust extracted from the mantle in arcs is refined into continental crust in subduction zones. During sediment subduction, subduction erosion, arc subduction, and continent subduction, mafic rocks become eclogite and may sink into the mantle, whereas more silica-rich rocks are transformed into felsic gneisses that are less dense than peridotite but more dense than the uppe...

Although the production of U-series disequilibria during metasomatic and partial-melting processes in Earth’s mantle is well studied, the effects of melting and assimilation processes during ascent and storage of magma in the crust are less well understood. To investigate disequilibria arising via this mechanism, we have conducted U-series measurements on the products of laboratory experiments ...

One of the fundamental geophysical observations made of the Earth is the stratified nature of the continental crust, in which the lower crust comprises denser, more mafic material and the upper crust comprises less dense, more felsic material. This chemically differentiated layered structure is developed and maintained by partial melting at depth and the ascent of magma to shallower crustal lev...

We model the ascent and eruption of lunar mare basalt magmas with new data on crustal thickness and density (GRAIL), magma properties, and surface topography, morphology and structure (Lunar Reconnaissance Orbiter). GRAIL recently measured the broad spatial variation of the bulk density structure of the crust of the Moon. Comparing this with the densities of lunar basaltic and picritic magmas s...

A model is presented to describe the cooling of the Earth in the Archaean. At the higher Archaean mantle temperatures pressure-release melting starts deeper and generates a thicker basaltic or komatiitic crust and depleted harzburgite layer compared with the present-day situation. Intrinsic compositional stability and lack of mechanical coherency renders the mechanism of plate tectonics ineffec...

Introduction: When a large hypervelocity impact occurs on a planetary body such as Mars, the kinetic energy of the impactor is partitioned primarily into 1) kinetic energy of the planetary crust and mantle as they deform and flow in response to the impact, 2) heating, melting and vaporization of impactor, crust and mantle material and 3) shockwaves that travel throughout the entire volume of th...

Magnetotelluric exploration has shown that the middle and lower crust is anomalously conductive across most of the north-to-south width of the Tibetan plateau. The integrated conductivity (conductance) of the Tibetan crust ranges from 3000 to greater than 20,000 siemens. In contrast, stable continental regions typically exhibit conductances from 20 to 1000 siemens, averaging 100 siemens. Such p...