The average chemical compositions of the continental crust and the oceanic crust (represented by MORB), normalized to primitive mantle values and plotted as functions of the apparent bulk partition coefficient of each element, form surprisingly simple, complementary concentration patterns. In the continental crust, the maximum concentrations are on the order of 50 to 100 times the primitive-man...

A fundamental challenge in modern mantle geochemistry is to link geochemical data with geological and geophysical observations. Most of the early geochemical models involved a layered mantle and the concept of geochemical reservoirs. Indeed, the two layer mantle model has been implicit in almost all geochemical literature and the provenance of oceanic island basalt (OIB) and mid-ocean ridge bas...

Earth’s dominant form of magmatism occurs at mid-ocean ridges (MORs), producing the igneous crust for two-thirds of the planet’s surface and conveying significant heat and material fluxes from the mantle to the world’s oceans. Mid-ocean-ridge basalt (MORB) magmas form from upwelling compositionally heterogeneous mantle1 by aggregation of near-fractional melts beneath spreading centres2. Multipl...

Lavas from Afanasy-Nikitin Rise, possibly the Late Cretaceous product of the Crozet hotspot, cover a wide range of isotopic compositions that includes the lowest (Pb/Pb)t (to 16.77) and «Nd(t) (to 28) values yet found among oceanic islands or spreading centers worldwide, as well as high (Sr/Sr)t (to 0.7066). In contrast, young basalts from the Crozet Archipelago exhibit a narrow range of variat...

Noble gas concentrations and isotopic compositions have been measured in eight samples of pillow basalt glasses collected from seven different localities along 250 km of the Mariana Trough spreading and rifting axis. The samples have uniform and mid-ocean ridge basalt (MORB)-like He/He values of 9±12 ́ 10 (6.4±8.6 times atmospheric) despite large variations in He. Concentrations of the noble ga...

The Jinshajiang–Ailaoshan–Song Ma orogenic belt (JASB), as a vital segment of the eastern Paleo-Tethyan tectonic zone, is one most important zones in which to study evolution. We have undertaken an integrated geochronological, petrological, and geochemical mafic rocks from JASB reveal subduction closure processes Ocean during Permian Triassic. In conjunction with previous magmatic metamorphic r...

Ž . We report Inductively Coupled Plasma Mass Spectrometer ICP-MS trace element concentration data for 21 elements in Ž 51 basaltic glasses recovered from 58 stations along a 1500-km segment of the equatorial mid-Atlantic Ridge MAR; 58N to . Ž 58S . Isotope systematics of these glasses revealed mixing between two isotopically distinct Schilling, J.-G., Hanan, B.B., McCully, B., Kingsley, R.H., ...

Magmas erupted at mid-ocean ridges (MORB) result from decompression melting of upwelling mantle. However, the mechanism of melt transport from the source region to the surface is poorly understood. It is debated whether melt is transported through melt-filled conduits or cracks on short time scales ( 10 yrs), or whether there is a significant component of slow, equilibrium porous flow on much l...

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