Tectonic Factors Controlling Formation of Heterogeneous Depleted Mantle

摘要

Overview and critical consideration of the available data characterizing the structure and composition of the depleted mantle lead to several important conclusions. Lherzolite and harzburgite are the main rock types in mantle parts of ophiolitic sections, among abyssal peridotites, and in mantle nodules entrained by basaltic lavas and kimberlites. These rocks are major constituents of the depleted mantle that extends from the crust/mantle boundary down to the maximum depth of MORB-type magma sources. The lithologic heterogeneity of the depleted mantle is evident from the extremely irregular distribution of these rocks in ophiolitic sections, where their mode of occurrence varies from fine intercalation to large monotonous domains, as well as from the combination of geochemical diversity of Iherzolites, harzburgites, and less abundant mantle rocks. The intramantle magmatic fractionation, subduction of oceanic lithospheric plates, and reactions of percolating melts and fluids with restitic peridotites are the main geodynamic factors that control compositional heterogeneity of the depleted mantle. The heterogeneous structure of the depleted mantle arose in the Early Precambrian and has evolved during the subsequent history of the Earth.