Highly Oxidising Conditions in Volatile-Rich El Hierro Magmas: Implications for Ocean Island Magmatism

Taracsák, Zoltán; Longpré, Marc‐Antoine; Tartèse, Romain; Burgess, Ray; Edmonds, Marie; Hartley, Margaret E.

doi:10.1093/petrology/egac011

Cited by 8 publications

(8 citation statements)

References 133 publications

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“…A previous investigation of Canary Islands OIB using XANES on relatively undegassed, olivine-hosted melt inclusions estimated a mantle source fO 2 of +2.0 ∆FMQ (Moussallam et al, 2019), consistent with the average Canary fO 2 determined in this study (+1.8 ∆FMQ). Canary lavas in this study range from +1.4 to +2.4 ∆FMQ, which overlaps with Canary lavas from other studies using the same proxy (D ol melt V ) that range from +1.3 to +3.9 ∆FMQ (Nicklas, Hahn, Willhite, et al, 2022;Taracsák et al, 2022).…”

Section: Offset Between Fo 2 Determined By Different Proxiessupporting

confidence: 75%

“…Other techniques in the compilation (n = 64)-including titrimetric determination of Fe 2+ and X-ray fluorescence for Fe T and MgO thermogeobarometry, etc.-yield even lower fO 2 with an average of +0.3 ∆FMQ. Some previous studies (e.g., Taracsák et al, 2022) have shown that the fO 2 values recorded by OIB via the D ol/melt V proxy are higher than fO 2 determined by other techniques, such as XANES measurements of Fe +3 /Fe T and S speciation (Figure 5c). However, recent work has demonstrated that Fe XANES and D ol/melt V produce concordant fO 2 results in MORB glasses with greater than 8.3 wt.…”

Section: Offset Between Fo 2 Determined By Different Proxiesmentioning

confidence: 66%

“…It has been shown that the subducted lithosphere retains most of its oxidized material during subduction (Brounce et al, 2019) and that a large mass of recycled lithosphere remains oxidized relative to the ambient mantle at ≥300 km depth due to the survival of carbonates in carbonated eclogites (Foley, 2011;Yaxley & Green, 1994). Thus, recycled lithosphere in plume sources has been cited to explain observations of elevated fO 2 in OIB compared to global MORB (Brounce et al, 2017;Hartley et al, 2017;Helz et al, 2017;Moussallam et al, 2014Moussallam et al, , 2016Moussallam et al, , 2019Nicklas, Hahn, Willhite, et al, 2022;Shorttle et al, 2015;Taracsák et al, 2022).…”

Section: The Role Of Lithospheric Recycling In Elevated Oib Fomentioning

confidence: 99%

“…% and whole-rocks with the highest CaO/ Al 2 O 3 (Figure 4; Figure S12 in Supporting Information S1). The addition of volatile, oxidizing agents such as C 4+ Geochemistry, Geophysics, Geosystems 10.1029/2023GC011249 and S 6+ hosted in subducted carbonated lithosphere to the mantle source has been invoked to account for the highly oxidized and volatile-rich HIMU lavas in El Hierro, Canary (Taracsák et al, 2022). The reduction of carbonate and sulfate will lead to the oxidation of silicates, as observed in arc settings (Rielli et al, 2017).…”

Section: Himu Lavasmentioning

confidence: 99%

“…In contrast, relatively well‐preserved mantle domains (i.e., that have not been modified by mixing with significant mass of recycled materials) host primitive isotopic signatures, such as high 3 He/ 4 He and anomalous μ 182 W (Farley et al., 1992; Hart et al., 1992; Jackson et al., 2020; Kurz et al., 1982; Mundl et al., 2017; Zindler & Hart, 1986). Recycled lithosphere in mantle plume sources might have played a role in generating higher f O 2 observed at Hawaii, Iceland, Canary, and Cape Verde relative to MORB (Brounce et al., 2017; Hartley et al., 2017; Helz et al., 2017; Moussallam et al., 2014, 2016, 2019; Nicklas, Hahn, Willhite, et al., 2022; Shorttle et al., 2015; Taracsák et al., 2022). However, not all individual OIB lavas are oxidized relative to MORB, which may reflect a lesser proportion of oxidized material and/or different types of recycled material in their respective source regions; and/or, derivation via petrogenetic processes that lower f O 2 , such crustal assimilation (Brounce et al., 2022; Nicklas, Hahn, & Day, 2022).…”

Section: Introductionmentioning

confidence: 99%

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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: Offset Between Fo 2 Determined By Different Proxiessupporting

confidence: 75%

Section: Offset Between Fo 2 Determined By Different Proxiesmentioning

confidence: 66%

Section: The Role Of Lithospheric Recycling In Elevated Oib Fomentioning

confidence: 99%

Section: Himu Lavasmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Oxygen Fugacity of Global Ocean Island Basalts

Willhite,

Arevalo,

Piccoli

et al. 2024

Geochem Geophys Geosyst

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Iron valence systematics in clinopyroxene crystals from ocean island basalts

Neave,

Stewart,

Hartley

et al. 2024

Contrib Mineral Petrol

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The valence state of Fe plays a vital role in setting and recording the oxidation state of magmas, commonly expressed in terms of oxygen fugacity ($$f_{\textrm{O}_{2}}$$ f O 2 ). However, our knowledge of how and why $$f_{\textrm{O}_{2}}$$ f O 2 varies within and between magmatic systems remains patchy because of diverse challenges associated with estimating the valence state of Fe in glasses and minerals routinely. Here we investigate Fe valence systematics in magmatic clinopyroxene crystals from ocean island basalts (OIBs) erupted in Iceland and the Azores to explore whether they record information about magma Fe$$^{3+}$$ 3 + contents and magmatic $$f_{\textrm{O}_{2}}$$ f O 2 conditions. Although many studies assume that all Fe in augitic clinopyroxene crystals from OIBs occurs as Fe$$^{2+}$$ 2 + , we find that up to half of the total Fe present can occur as Fe$$^{3+}$$ 3 + , with crystals from alkali systems typically containing more Fe$$^{3+}$$ 3 + than those from tholeiitic systems. Thus, Fe$$^{3+}$$ 3 + is a major if under-appreciated constituent of augitic clinopyroxene crystals erupted from ocean island volcanoes. Most Fe$$^{3+}$$ 3 + in these crystals is hosted within esseneite component (CaFe$$^{3+}$$ 3 + AlSiO$$_{6}$$ 6 ), though some may be hosted in aegirine component (NaFe$$^{3+}$$ 3 + Si$$_{2}$$ 2 O$$_{6}$$ 6 ) in crystals from alkali systems. Observations from samples containing quenched matrix glasses suggest that the incorporation of Fe$$^{3+}$$ 3 + is related to the abundance of tetrahedrally coordinated Al ($$\mathrm {^{IV}}$$ IV Al), implying some steric constraints over Fe$$^{3+}$$ 3 + partitioning between clinopyroxene and liquid (i.e., $$D\mathrm {^{{cpx-liq}}_{{Fe_{2}O_{3}}}}$$ D Fe 2 O 3 cpx - liq values), though this may not be an equilibrium relationship. For example, $$\mathrm {^{IV}}$$ IV Al-rich $$\{hk0\}$$ { h k 0 } prism sectors of sector-zoned crystals contain more Fe$$^{3+}$$ 3 + than $$\mathrm {^{IV}}$$ IV Al-poor $$\{\bar{1}11\}$$ { 1 ¯ 11 } hourglass sectors. Moreover, $$\mathrm {^{IV}}$$ IV Al-rich compositions formed during disequilibrium crystallisation are enriched in Fe$$^{3+}$$ 3 + . Apparent clinopyroxene-liquid Fe$$^{2+}$$ 2 + –Mg exchange equilibria (i.e., $$K\mathrm{{_{D, {Fe^{2+}-Mg}}^{cpx-liq}}}$$ K D , Fe 2 + - Mg cpx - liq values) are similarly affected by disequilibrium crystallisation in our samples. Nonetheless, it is possible to reconcile our observed clinopyroxene compositions with glass Fe valence systematics estimated from olivine-liquid equilibria if we assume that $$K\mathrm{{_{D, {Fe^{2+}-Mg}}^{cpx-liq}}}$$ K D , Fe 2 + - Mg cpx - liq values lies closer to experimentally reported values of 0.24$$-$$ - 0.26 than values of $$\sim$$ ∼ 0.28 returned from a general model. In this case, olivine-liquid and clinopyroxene-liquid equilibria record equivalent narratives, with one of our glassy samples from Iceland recording evolution under $$f_{\textrm{O}_{2}}$$ f O 2 conditions about one log unit above fayalite-magnetite-quartz (FMQ) equilibrium (i.e., $$\sim$$ ∼ FMQ+1) and our glassy Azorean sample recording evolution under significantly more oxidising conditions ($$\ge$$ ≥ FMQ+2.5) before experiencing syn-eruptive reduction, likely as a result of SO$$_{2}$$ 2 degassing; our other glassy sample from Iceland was also affected by reductive SO$$_{2}$$ 2 degassing. Overall, our findings demonstrate that the Fe valence systematics of clinopyroxene crystals can record information about the conditions under which OIBs evolve, but that further experimental work is required to properly disentangle the effects of magma composition, disequilibrium and $$f_{\textrm{O}_{2}}$$ f O 2 conditions on clinopyroxene-liquid equilibria involving Fe$$^{2+}$$ 2 + and Fe$$^{3+}$$ 3 + .

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