The mantle source of basalts from Reunion Island is not more oxidized than the MORB source mantle

Abstract

Glasses quenched from relatively undegassed ocean island magmas erupted from volcanoes at Iceland, Hawaii, the Canary Islands, and Erebus have elevated Fe3+/∑Fe ratios compared to glasses quenched from mid-ocean ridge basalts. This has been ascribed to elevated fO2 of their mantle sources, plausibly due to subducted, oxidized near-surface-derived components in their mantle sources. The basaltic magmas from Reunion Island in the Indian ocean have Sr–Nd-Hf-Pb-Os isotopic compositions suggesting that their mantle sources contain little or no subducted near-surface materials and contain the C/FOZO/PREMA mantle component. To constrain the fO2 of the C/FOZO/PREMA mantle component and test the link between oxidized OIB and recycled surface-derived materials in their sources, we measured major and volatile element abundances and Fe3+/∑Fe ratios of naturally glassy, olivine-hosted melt inclusions from Piton de La Fournaise volcano, La Reunion. We conclude that the fO2 of the mantle source of these Reunion lavas is lower than of the mantle sources of primitive, undegassed magmas from Hawaii, Iceland, the Canary Islands, and Mt. Erebus, and indistinguishable from that of the Indian-ocean upper mantle. This finding is consistent with previous suggestions that the source of Reunion lavas (and the C/FOZO/PREMA mantle component) contains little or no recycled materials and with the suggestion that recycled oxidized materials contribute to the high fO2 of some other OIBs, especially those from incompatible-element-enriched mantle sources. Simple mixing models between oxidized melts of EM1 and HIMU components and relatively reduced melts of DMM can explain the isotopic compositions and Fe3+/∑Fe ratios of lavas from Hawaii, Iceland, the Canary Islands, and Mount Erebus; this model can be tested by study of additional OIB magmas, including those rich in the EM2 component.

Supplemental Material: Physical transport of magmatic sulfides promotes copper enrichment in hydrothermal ore fluids

“…Their anhydrous model composition (Table S1) was varied by adding a fixed quantity of FeS (0.5 wt%) and variable concentrations of H2O between 3 and 6 wt% (a range considered to be ideal for subsequent hydrothermal ore formation; Chiaradia, 2020), and by varying the bulk Fe III /Fe tot ratio between 0.18 and 0.48 at given FeO tot . This variation covers the range of Fe III /Fe tot reported from modellingindependent Fe-XANES measurements on silicate melt inclusions (~ 0.15 -0.4; (Kelley and Cottrell, 2009;Brounce et al, 2022).…”

The Oxidation State of Sulfur in Apatite of Martian Meteorite—Shergotty

“…The presence of sulfide‐only apatite in Shergotty is the first measurement of sulfide only apatite in the meteorite record, and the first observation of sulfide‐only apatite from Mars (c.f., Brounce, Stolper, & Eiler, 2022). The presence of sulfide‐only apatite in Shergotty suggests some small impact on calculations of the abundance of OH by difference, which also occupies the column anionic site where S 2− substitutes (Boyce et al., 2010).…”

“…The model fits for the reduced data are produced using the Fityk software (Wojdyr, 2010). Also plotted are the S 6+ /∑S ratio of both apatite and cracks within apatite from Apollo 11 and 12 lunar rocks (Brounce et al, 2019), Phillips mine apatite from New York (Sadove et al, 2019), Nakhla apatite (Brounce, Stolper, & Eiler, 2022), and Durango apatite (Brounce et al, 2019).…”

“…Alternative oxybarometers are thus necessary to use as proxies to measure fO 2 . As we have seen from studies on Earth, differentiation can result in a change in fO 2 (Berry et al, 2018;Brounce et al, 2016Brounce et al, , 2017Brounce, Stolper, & Eiler, 2022;Brounce, Boyce, & McCubbin, 2022;Brounce et al, 2014;Cottrell & Kelley, 2011;Hartley et al, 2017;Helz et al, 2017;Kelley & Cottrell, 2012;Le Voyer et al, 2015;Moussallam et al, 2014Moussallam et al, , 2019O'Neill et al, 2018;Shorttle et al, 2015), but such impacts of differentiation on fO 2 on Mars are yet to be quantified, and martian rock compositions, including volatiles and fO 2 , are different enough from terrestrial rocks that assuming an equivalent effect for martian and terrestrial magmas may be in error.…”

“…At the fO 2 values expected for martian meteorites, S is expected to be present in the melt as S 2− or as a combination of S 2− and S 6+ (Bothcarnikov et al, 2011;Jugo et al, 2010;Klimm et al, 2012;Matjuschkin et al, 2016;Nash et al, 2019). Consequently, apatite crystallizing from martian melts is reasonably expected to contain only S 2− in some cases (i.e., in apatite which crystallized from silicate liquids with fO 2 of <∆IW+3; e.g., Shergotty, QUE94201 and other shergottites), and mixtures of both S 2− and S 6+ in others (i.e., in apatite which crystallized from silicate liquids with fO 2 ∆IW > 3; e.g., Nakhlites, Chassignites), of which the latter was demonstrated by Brounce, Stolper, and Eiler (2022).…”