Basalts convective mixing

In summary, we have recently witnessed a shift away from the classically layered mantle model in favor of whole mantle convection models, where the buoyancy of sinking slabs is the dominant driving force. Slabs can penetrate deep into the lower mantle and with the induced return flow we would expect the mantle to mix efficiently. This leaves us with an interesting dilemma. If the mantle convects as a whole, how can it preserve the large-scale and long-hved heterogeneity seen in the geochemistry of oceanic basalts ... 

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