Combined Lithophile-Siderophile Isotopic Constraints on Hadean Processes Preserved in Ocean Island Basalt Sources

Detection of Hadean isotopic signatures within modern ocean island basalts (OIB) has greatly influenced understanding of Earth's earliest history and long-term dynamics. However, a relationship between two isotopic tools for studying early Earth processes, the short-lived Sm-146-Nd-142 and Hf-182-W-182 systems, has not been established in this context. The differing chemical behavior of these two isotopic systems means that they are complementary tracers of a range of proposed early Earth events, including core formation, magma ocean processes, and late accretion. There is a negative trend between Nd-142/Nd-144 and W-182/W-184 ratios among Reunion OIB that is extended by Deccan continental flood basalts. This finding is contrary to expectations if both systems were affected by silicate differentiation during the lifetime of Hf-182. The observed isotopic compositions are attributed to interaction between magma ocean remnants and Earth's core, coupled with later assimilation of recycled Hadean mafic crust. The effects of this scenario on the long-lived Nd-143-Hf-176 isotopic systematics mirror classical models invoking mixing of recycled trace-element enriched (sedimentary) and depleted (igneous) domains in OIB mantle sources.