Mantle sources of ocean islands basalts revealed from noble gas isotope systematics

Day, James M.D.; Jones, T. D.; Nicklas, Robert W.

doi:10.1016/j.chemgeo.2021.120626

Cited by 22 publications

(2 citation statements)

References 153 publications

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“…For all lavas with published He and/or W isotopes in this study, there is no statistically significant correlation with f O 2 (Figure 8); however, high 3 He/ 4 He lavas are limited in this data set, and only 10 lavas have 3 He/ 4 He above 10 Ra. In previous studies of noble gas systematics in OIB, all studied OIB had higher f O 2 than MORB, regardless of 3 He/ 4 He (Day et al., 2022). Typically, OIB with a higher proportion of recycled material (i.e., a greater D Sr−Nd−Pb ) fall along mixing lines between MORB and various recycled end members with higher Fe 3+ /∑Fe (Brounce et al., 2022).…”

Section: Discussionmentioning

confidence: 83%

Oxygen Fugacity of Global Ocean Island Basalts

Willhite,

Arevalo,

Piccoli

et al. 2024

Geochem Geophys Geosyst

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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 fO2 and 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 fO2 in OIB is heterogeneous both within and among hotspots. Taken together with previous studies, global OIB have elevated and heterogenous fO2 (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 fO2 based on statistical analysis. Elevated fO2 in OIB samples of these components is associated with higher whole‐rock CaO/Al2O3 and 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 fO2 among EM1‐, EM2‐, and HIMU‐type OIB, geochemical indices of lithospheric recycling, such as Sr‐Nd‐Pb‐Os isotopic systems, generally do not correlate with fO2.

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Section: Discussionmentioning

confidence: 83%

Oxygen Fugacity of Global Ocean Island Basalts

Willhite,

Arevalo,

Piccoli

et al. 2024

Geochem Geophys Geosyst

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“…d. Largest observed negative deviations in μ 182 W compiled from (Mundl et al, 2017;Rizo et al, 2019;Mundl-Petermeier et al, 2020). Note that the largest deviations for He and W do not always occur in the same samples for a given hotspot, and hotspots might be affected to different degrees by overprinting by recycled crust (Parai et al, 2019;Jackson et al, 2020;Péron et al, 2021;Day, Jones and Nicklas, 2022). Additionally, both the compilations of the ULVZs and the isotopic anomalies have a degree of geographical bias to where (more) studies have been conducted.…”

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The root to the Galápagos mantle plume on the core-mantle boundary

Cottaar¹,

Martin²,

Li³

et al. 2022

Preprint

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Ultra-low velocity zones (ULVZs) are thin anomalous patches on the boundary between the Earth's core and mantle, revealed by their effects on the seismic waves that propagate through them. Here we map a broad ULVZ near the Galápagos hotspot using shear-diffracted waves. Forward modelling assuming a cylindrical shape shows the patch is ~600 km wide, ~20 km high, and its shear velocities are ~25% reduced. The ULVZ is comparable to other broad ULVZs mapped on the core-mantle boundary near Hawaii, Iceland, and Samoa. Strikingly, all four hotspots where the mantle plume appears rooted by these ‘mega-ULVZs’, show similar anomalous isotopic signatures in He, Ne, and W in their ocean island basalts. This correlation suggests mega-ULVZs might be primordial or caused by interaction with the core, and some material from ULVZs is entrained within the plume. For the Galápagos, the connection implies the plume is offset to the west towards the base of the mantle.

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