Global mantle isotopic anomalies linked to supercontinent-superocean evolution for the past 700 million years

Abstract

Abstract Earth’s mantle isotopic composition is highly heterogeneous, with enriched and depleted regions1–3 shaped by a complex history of depletion and re-enrichment over 4.5 billion years. The spatial configuration of large-scale heterogeneity in the mantle is not random4,5, but the timing and mechanisms that caused such heterogeneity are still debated2,6,7. We compiled radiogenic isotope data of mid-ocean ridge and plume-induced basalts from both present-day and past oceans for the past 900 million years of the relatively isotopically enriched African mantle domain. Our analysis shows that oceanic rocks of the African mantle domain exhibit a relatively homogenous composition similar to the prevalent mantle estimates (PREMA8) until ca. 350 million years ago when plume-derived rocks started becoming isotopically enriched with maximum enrichment reached in the mid-Cretaceous. From that point in time, plume-derived rocks shift toward depletion, getting closer to the prevalent mantle value. The enrichment trend is interpreted to have resulted from the recycling of crustal material during the assembly and the early stage of a break-up of Gondwana and Pangea, whereas the subsequent depletion trend is due to the outward retreat of the subduction girdle during the break-up of Pangea, thus both are legacies of geodynamic processes related to the supercontinent cycle.