Molybdenum isotope systematics of lavas from the East Pacific Rise: Constraints on the source of enriched mid-ocean ridge basalt

Mid-ocean ridge basalts (MORB) reveal large mantle compositional heterogeneity, whose origin remains debated. Here we present a systematic study of molybdenum isotopes on well-characterized MORB glass samples from the East Pacific Rise (EPR) and near-EPR seamounts. Our analyses show significant Mo isotope variations with δ98/95Mo (relative to NIST SRM3134) ranging −0.23‰ −0.06‰. We argue that these are not caused by processes melt generation evolution but reflect isotopic heterogeneity. Taking together literature data, compositions vary systematically geochemical parameters indicating enrichment. These observations best explained two-component mixing between an incompatible element depleted endmember (e.g., low La/Sm, Nb/La, Nb/Zr Th/Yb, high Sm/Nd 143Nd/144Nd) (∼−0.21‰) enriched (∼−0.05‰). The association heavier geochemically more is inconsistent recycled ocean crust or without sediment being endmember. Instead, this consistent magmatic origin, most likely lithologies low-degree metasomatic dispersed in peridotite matrix mantle. Thus, systematics, confirm oceanic lithosphere metasomatized degree plays key role formation E-MORB source lithologies. also highlights as effective tool for studying upper processes.