Differentiation of the earth's mantle (According to geochemical data)

The distribution characteristics of the petrogenic and trace elements in the mantle-derived xenoliths and in the products of the mantle magmatism are discussed. It is shown that variations in the concentrations of the major elements in the mantle rocks reflect processes of large-scale partial melting, while shifts in the ratios of highly incompatible components in the mantle reservoirs are related to the movements of melts in the partially melted matter or to the removal of some fluid which was in equilibrium with the convective mantle. Data on the isotope geochemistry and on the distribution of rare elements in alkaline igneous complexes indicate that their mantle source was depleted in the course of a long period of time in the past, and then was enriched in incompatible elements just before the beginning of the generation of primary alkaline magmas.