Excess volcanism and crustal swelling associated with hot spots are generally attributed to thermal plumes upwelling from the mantle. This concept has been tested in the portion of the Mid-Atlantic Ridge between 34 degrees and 45 degrees (Azores hot spot). Peridotite and basalt data indicate that the upper mantle in the hot spot has undergone a high degree of melting relative to the mantle else...

[1] Phase equilibrium experiments on primitive Miocene olivine leucitite (Bb-107) from the Qiangtang terrane of the Tibetan Plateau were performed from 1.0 to 2.2 GPa and 1270 to 1440 C. The composition is multiply saturated with olivine and clinopyroxene from 1.2 to 2.2 GPa and 1340 C under nominally anhydrous conditions. Phase assemblages in the experiments have been used to model the effects...

We apply a tool based on element distribution between orthopyroxene and clinopyroxene for quantifying rare earth element (REE) disequilibria in ultramafic rocks in the subsolidus state. We present case studies of the REE contents of mineral cores in mantle xenoliths and abyssal peridotites using in situ analytical tools. Even when only mineral cores are measured (to avoid enriched rims), equili...

in taleghan, olivine basalt-basaltic andesite dykes as part of tertiary mamgmatic activities in central and western alborz zone, intruded into both karaj formation and late eocene-oligocene volcanic rocks. these dykes have similar geochemical characteristic which suggest that they are originated from a common source. on the primitive mantle normalized spider diagram, the dykes are characterized...

The Ontong Java and Manihiki oceanic plateaus are believed to have formed through high-degree melting of a mantle plume head. Boninite-like, low-Ti basement rocks at Manihiki, however, imply a more complex magma genesis compared with Ontong Java basement lavas that can be generated by ∼30% melting of a primitive mantle source. Here we show that the trace element and isotope compositions of low-...

Introduction: Mantle derived peridotite xenoliths ranging in modal composition between fertile lherzolites and modally metasomatized harzburgites has been analyzed by instrumental neutron activation analysis (INAA) for As, Sb and REE. In many melt depleted mantle samples (harzburgites) the incompatible element concentrations are much higher than those estimated for the fertile mantle. The reaso...

Plate subduction continuously transports crustal materials with high-δ(18)O values down to the mantle wedge, where mantle peridotites are expected to achieve the high-δ(18)O features. Elevated δ(18)O values relative to the upper mantle value have been reported for magmas from some subduction zones. However, peridotites with δ(18)O values significantly higher than the well-defined upper mantle v...

Bulk-rock geochemical compositions of hypabyssal kimberlites, emplaced through the Archaean Kaapvaal craton and Proterozoic Namaqua–Natal belt, are used to estimate close-to-primary magma compositions of Group I kimberlites (Mg-number 1⁄4 0 82–0 87; 22–28 wt % MgO; 21–30 wt % SiO2; 10–17 wt % CaO; 0 2–1 7 wt % K2O) and Group II kimberlites (Mgnumber 1⁄4 0 86–0 89; 23–29 wt % MgO; 28–36 wt % SiO...

Abstract For porphyry Cu deposits that formed during oceanic slab subduction, there is a general consensus the ore-forming magmas evolved through fractionation of mafic were generated by fluid (± melt)–fluxed melting asthenospheric mantle wedge. This model, however, not applicable to post-subduction because they distinctly after cessation subduction. A popular model proposes produced partial lo...