Variations in the geochemical and isotopic characteristics of residual peridotites along the mid-atlantic ridge as a function of the nature of the mantle magmatic sources

The paper presents one of the first attempts to reproduce the nature of the mantle sources of magmatism beneath the MAR rift valley by comparing the petrologic and geochemical parameters of residual peridotites and related basalts. The geochemical MAR segmentation is demonstrated to be clearly pronounced not only in the axial basalts but also in the related mantle residues. The indicator petrological-geochemical parameters of mantle residues from the plume and spreading MAR segments are well correlated with the corresponding parameters of the related basalts. The MAR axial zone north of the Equator contains two principal groups of mantle peridotites. The group-I peridotites genetically correspond to the related basalts. The group-II mantle residues are characterized by the absence of isotopic genetic relations with the products of basaltic magmatism in the rift zone of the northern MAR. The mechanism of high-temperature metasomatic interaction between the within-plate melts of the OIB type and the depleted mantle material facilitated the origin of a broad spectrum of MORB, which are widespread in the northern MAR plume regions. Magmatism in the spreading MAR segments is characterized by moderate and low partial melting degrees and shows no apparent traces of the involvement of enriched within-plate melts. The MAR axial zone north of the Equator includes mantle peridotites, which are the material of the subcontinental lithospheric mantle that did not contribute to the origin of the modem magmatic associations of the rift valley.