14/10 Séminaires Généraux: Oliver Shorttle (Cambridge), ENS amphi L
Estimating the amount of recycled material in the mantle
from basalt chemistry
As the primary flux of material from the mantle to the surface, the basalts erupted at mid-ocean ridges (MORB) are a key resource for investigating the mantle’s chemical composition. However, despite the large volumes of oceanic crust returned to the mantle by subduction, it has proven difficult to find clear evidence of this material’s involvement in melt production using the chemistry of MORB. Even more uncertain is the abundance of this recycled material in the source when present. This is a significant problem, as fundamental questions about the dynamics of our planet cannot be answered without quantifying the abundance and spatial distribution of the mantle’s chemical heterogeneity: to what extent do the shallow and deep mantle communicate? What is the eventual fate of recycled oceanic material? What are the fluxes of elements from the deep Earth to the surface? Here, we present a method to estimate the proportion of enriched material in mantle source regions by combining geochemical observations, crustal thickness estimates and thermodynamic models of mantle of mantle melting.
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