Plate tectonics drive compositional evolution of the upper mantle, study finds

On present-day Earth, plate subduction continuously modifies the chemical composition of the convecting mantle, and various mantle sources linked to these processes have been widely studied. However, when did global chemical heterogeneity of the convecting mantle first emerge in Earth's geological history? How might Earth's geodynamic evolution have influenced the chemical composition of the convecting mantle over time?