Main components of geochemical reservoirs of the silicate Earth

Mass balance of incompatible elements was analyzed for different inferred reservoirs of the bulk silicate Earth. It was shown that the lower mantle, as well as the primitive mantle, includes an MORB-source depleted mantle component and material with a high content of incompatible elements. Contribution of the continental crust was found to be subordinate. The predominant part of the enriched mantle formed through differentiation of the mantle itself. Enriched material was supplied into the deep-seated zones of silicate shell through delamination of subcontinental lithospheric blocks affected by mantle metasomatism and their subsequent involvement in the mantle convective system. The osmium isotope composition of the plunged lithospheric material is modified in the lower mantle by the infiltration of sulfide melts.