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1. Testing the Recycled Gabbro Hypothesis for the Origin of “Ghost Plagioclase” Melt Signatures Using 87 Sr/ 86 Sr of Individual Olivine‐Hosted Melt Inclusions From Hawai'i

   https://doi.org/10.1029/2020GC009260  

   Anderson, O. E. ; Jackson, M. G. ; Rose‐Koga, E. F. ; Marske, J. P. ; Peterson, M. E. ; Price, A. A. ; Byerly, B. L. ; Reinhard, A. A. ( April 2021 , Geochemistry, Geophysics, Geosystems)

   Melt inclusions with large, positive Sr anomalies have been described in multiple tectonic settings, and the origins of this unusual geochemical feature are debated. Three origins have been proposed, all involving plagioclase as the source of the elevated Sr: (i) direct assimilation of plagioclase‐rich lithologies, (ii) recycled lower oceanic gabbro in the mantle source, and (iii) shallow‐level diffusive interaction between present day lower oceanic crust (i.e., plagioclase‐bearing lithologies) and the percolating melt. A “ghost plagioclase” signature (i.e., a large, positive Sr anomaly without associated high Al₂O₃) is present in melt inclusions from Mauna Loa. We present new⁸⁷Sr/⁸⁶Sr measurements of individual olivine‐hosted melt inclusions from three Hawaiian volcanoes, Mauna Loa, Loihi, and Koolau. The data set includes a Mauna Loa melt inclusion with the highest reported Sr anomaly (or highest (Sr/Ce)_N, which is 7.2) for Hawai'i. All melt inclusions have⁸⁷Sr/⁸⁶Sr values within the range reported previously for the lavas from each volcano. Critically, the⁸⁷Sr/⁸⁶Sr of the high (Sr/Ce)_Nmelt inclusion lies within the narrow range of⁸⁷Sr/⁸⁶Sr for Mauna Loa melts that lack high (Sr/Ce)_Nsignatures. Therefore, to explain the high (Sr/Ce)_Nratio of the ghost plagioclase signature using an ancient recycled gabbro, the gabbro‐infused mantle source would have had to evolve, by chance, to have the same⁸⁷Sr/⁸⁶Sr as the source of the Mauna Loa melts that lack a recycled gabbro (ghost plagioclase) signature. Alternatively, shallow‐level diffusive interactions between Mauna Loa plagioclase‐rich cumulates and a percolating mantle‐derived melt provides a simpler explanation for the presence of the high (Sr/Ce)_NMauna Loa melts.

    

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2. Long-term storage of subduction-related volatiles in Northern Victoria Land lithospheric mantle: Insight from olivine-hosted melt inclusions from McMurdo basic lavas (Antarctica)

   https://doi.org/10.1016/j.lithos.2020.105826  

   Giacomoni, P.P. ; Bonadiman, C. ; Casetta, F. ; Faccini, B. ; Ferlito, C. ; Ottolini, L. ; Zanetti, A. ; Coltorti, M. ( December 2020 , Lithos)
3. The volatile budget of Hawaiian magmatism: Constraints from melt inclusions from Haleakala volcano, Hawaii

   https://doi.org/10.1016/j.jvolgeores.2020.107144  

   Moore, L.R. ; Gazel, E. ; Bodnar, R.J. ( February 2021 , Journal of Volcanology and Geothermal Research)

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4. Oxygen and Al‐Mg isotopic compositions of grossite‐bearing refractory inclusions from CO 3 chondrites

   https://doi.org/10.1111/maps.13282  

   Simon, Steven B. ; Krot, Alexander N. ; Nagashima, Kazuhide ( April 2019 , Meteoritics & Planetary Science)

   The distribution of the short‐lived radionuclide²⁶Al in the early solar system remains a major topic of investigation in planetary science. Thousands of analyses are now available but grossite‐bearing Ca‐, Al‐rich inclusions (CAIs) are underrepresented in the database. Recently found grossite‐bearing inclusions inCO3 chondrites provide an opportunity to address this matter. We determined the oxygen and magnesium isotopic compositions of individual phases of 10 grossite‐bearingCAIs in the Dominion Range (DOM) 08006 (CO3.0) andDOM08004 (CO3.1) chondrites. All minerals inDOM08006CAIs as well as hibonite, spinel, and pyroxene inDOM08004 are uniformly¹⁶O‐rich (Δ¹⁷O = −25 to −20‰) but grossite and melilite inDOM08004CAIs are not; Δ¹⁷O of grossite and melilite range from ~ −11 to ~0‰ and from ~ −23 up to ~0‰, respectively. Even within this small suite, in the two chondrites a bimodal distribution of the inferred initial²⁶Al/²⁷Al ratios (²⁶Al/²⁷Al)₀is seen, with four having (²⁶Al/²⁷Al)₀≤1.1 × 10⁻⁵and six having (²⁶Al/²⁷Al)₀≥3.7 × 10⁻⁵. Five of the²⁶Al‐richCAIs have (²⁶Al/²⁷Al)₀within error of 4.5 × 10⁻⁵; these values can probably be considered indistinguishable from the “canonical” value of 5.2 × 10⁻⁵given the uncertainty in the relative sensitivity factor for grossite measured by secondary ion mass spectrometry. We infer that the²⁶Al‐poorCAIs probably formed before the radionuclide was fully mixed into the solar nebula. All minerals in theDOM08006CAIs, as well as spinel, hibonite, and Al‐diopside in theDOM08004CAIs retained their initial oxygen isotopic compositions, indicating homogeneity of oxygen isotopic compositions in the nebular region where theCOgrossite‐bearingCAIs originated. Oxygen isotopic heterogeneity inCAIs fromDOM08004 resulted from exchange between the initially¹⁶O‐rich (Δ¹⁷O ~−24‰) melilite and grossite and¹⁶O‐poor (Δ¹⁷O ~0‰) fluid during hydrothermal alteration on theCOchondrite parent body; hibonite, spinel, and Al‐diopside avoided oxygen isotopic exchange during the alteration. Grossite and melilite that underwent oxygen isotopic exchange avoided redistribution of radiogenic²⁶Mg and preserved undisturbed internal Al‐Mg isochrons. The Δ¹⁷O of the fluid can be inferred from O‐isotopic compositions of aqueously formed fayalite and magnetite that precipitated from the fluid on theCOparent asteroid. This and previous studies suggest that O‐isotope exchange during fluid–rock interaction affected mostCAIs in CO ≥3.1 chondrites.

    

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5. A high carbon content of the Hawaiian mantle from olivine-hosted melt inclusions

   https://doi.org/10.1016/j.gca.2019.04.001  

   Tucker, Jonathan M. ; Hauri, Erik H. ; Pietruszka, Aaron J. ; Garcia, Michael O. ; Marske, Jared P. ; Trusdell, Frank A. ( June 2019 , Geochimica et Cosmochimica Acta)