English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Open

Although more and more robust evidence for whole mantle convection comes from seismic tomography and geoid modeling, the rare gases and other isotopic or trace element signatures of ridge and hotspot basalts indicate the presence of various isolated geochemical reservoirs in the mantle. We discuss this discrepancy between fluid dynamic views of mantle convection and chemical observations. We compare the standard model of geodynamicists where the mantle behaves as a fluid mostly heated from within with the findings of seismic tomography. We suggest that a significant part of the subducted oceanic crust transforms into dense eclogitic assemblages, and partially segregates to form a layer that has grown with time above the Core Mantle Boundary (CMB) and should correspond to the D" layer of seismological models ( 280 km thick). We show how a two component marble cake mantle filling the whole mantle except D" can account for the variability of Ocean Island Basalts (OIB) and Mid-Ocean Ridge Basalts (MORB) in rare gases. We then present the state of the art in thermochemical convection of the mantle and emphasize the numerical and conceptual progress that must be made to provide a quantitative test of the geochemical hypotheses.

Geophysical and geochemical models of mantle convection: Successes and future challenges