Journal ArticleOxygen Fugacity of Global Ocean Island BasaltsWillhite, Lori N; Arevalo, Ricardo; Piccoli, Philip; Lassiter, John C; Rand, Devin; Jackson, Matthew G; Day, James_M D; Nicklas, Robert W; Locmelis, Marek; Ireland, Thomas J; Puchtel, Igor S<title>Abstract</title> <p>Mantle plumes contain heterogenous chemical components and sample variable depths of the mantle, enabling glimpses into the compositional structure of Earth's interior. In this study, we evaluated ocean island basalts (OIB) from nine plume locations to provide a global and systematic assessment of the relationship between<italic>f</italic>O₂and He‐Sr‐Nd‐Pb‐W‐Os isotopic compositions. Ocean island basalts from the Pacific (Austral Islands, Hawaii, Mangaia, Samoa, Pitcairn), Atlantic (Azores, Canary Islands, St. Helena), and Indian Oceans (La Réunion) reveal that<italic>f</italic>O₂in OIB is heterogeneous both within and among hotspots. Taken together with previous studies, global OIB have elevated and heterogenous<italic>f</italic>O₂(average = +0.5 ∆FMQ; 2SD = 1.5) relative to prior estimates of global mid‐ocean ridge basalts (MORB; average = −0.1 ∆FMQ; 2SD = 0.6), though many individual OIB overlap MORB. Specific mantle components, such as HIMU and enriched mantle 2 (EM2), defined by radiogenic Pb and Sr isotopic compositions compared to other OIB, respectively, have distinctly high<italic>f</italic>O₂based on statistical analysis. Elevated<italic>f</italic>O₂in OIB samples of these components is associated with higher whole‐rock CaO/Al₂O₃and olivine CaO content, which may be linked to recycled carbonated oceanic crust. EM1‐type and geochemically depleted OIB are generally not as oxidized, possibly due to limited oxidizing potential of the recycled material in the enriched mantle 1 (EM1) component (e.g., sediment) or lack of recycled materials in geochemically depleted OIB. Despite systematic offset of the<italic>f</italic>O₂among EM1‐, EM2‐, and HIMU‐type OIB, geochemical indices of lithospheric recycling, such as Sr‐Nd‐Pb‐Os isotopic systems, generally do not correlate with<italic>f</italic>O₂.</p>Wiley Periodicals LLC2024-01-0110512051Geochemistry, Geophysics, Geosystems2511525-2027https://doi.org/10.1029/2023GC0112491944552; 2503213National Science Foundation