doi:10.5194/se-2-159-2011 © Author(s) 2011. CC Attribution 3.0 License. Solid Earth

Abstract. The reconciliation of mantle chemistry with the structure of the mantle inferred from geophysics and dynam-ical modelling has been a long-standing problem. This paper reviews three main aspects. First, extensions and refinements of dynamical modelling and theory of mantle processing over the past decade. Second, a recent reconsideration of the im-plications of mantle heterogeneity for melting, melt migra-tion, mantle differentiation and mantle segregation. Third, a recent proposed shift in the primitive chemical baseline of the mantle inferred from observations of non-chondritic 142Nd in the Earth. It seems most issues can now be resolved, except the level of heating required to maintain the mantle’s thermal evolution. A reconciliation of refractory trace elements and their iso-topes with the dynamical mantle, proposed and given pre-liminary quantification by Hofmann, White and Christensen, has been strengthened by work over the past decade. The ap-parent age of lead isotopes and the broad refractory-element differences among and between ocean island basalts (OIBs) and mid-ocean ridge basalts (MORBs) can now be quantita-tively accounted for with some assurance. The association of the least radiogenic helium with rel-atively depleted sources and their location in the mantle have been enigmatic. The least radiogenic helium samples have recently been recognised as matching the proposed non-chondritic primitive mantle. It has also been proposed re-cently that noble gases reside in a so-called hybrid pyroxen-ite assemblage that is the result of melt from fusible pods re-acting with surrounding refractory peridotite and refreezing. Hybrid pyroxenite that is off-axis may not remelt and erupt at MORs, so its volatile constituents would recirculate within the mantle. Hybrid pyroxenite is likely to be denser than av-erage mantle, and thus some would tend to settle in the D′