Heavy <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si46.svg"><mml:mrow><mml:mi>?</mml:mi></mml:mrow></mml:math>57Fe in ocean island basalts: A non-unique signature of processes and source lithologies in the mantle

Lithological heterogeneity is a widely accepted feature of the Earth’s mantle, with recycled crustal material accounting for significant part in ocean island basalt (OIB) geochemistry. Fe isotopes have been used to link geochemical OIB sources distinct mantle lithologies due their mineral-specific equilibrium fractionation effects, or composition, such as incorporation kinetically-fractionated core liquids entrained from core-mantle boundary. Here we present isotope data Samoan shield, and Azores volcanoes, together combined phase-equilibria mineral-melt model. These lavas allow us study roles core-derived components generating heavy ?57Fe melts. Heavy correlates radiogenic signatures enrichment by component not Fe/Mn any indicator involvement. However, single-stage melting MORB-like eclogitic pyroxenite cannot generate seen Pitcairn, Azores, rejuvenated Samoa lavas. Melts reaction-zone (commonly suggested form source), derived eclogite melts hybridised peridotite, also fail heaviest isotopic compositions OIB. Instead, generation requires: (1) processes that make subducted isotopically heavier than its pristine precursor MORB (e.g., hydrothermal alteration, metamorphism, sediment input); (2) lithospheric processing, remobilisation previously frozen small-degree melts, contribution metasomatised silicate melts; and/or (3) conditions limit dilution ambient lower materials. No single process consider can Therefore, it be assumed lithology sole producer OIB, nor these related contributions core. observation ascribed unique source process. This ambiguity reflects multitude operating through melting: generation, low temperature development eruption at islands.