Oxidising agents in sub-arc mantle melts link slab devolatilisation and arc magmas

Antoine Bénard*, Kevin Klimm, Alan B. Woodland, Richard J. Arculus, Max Wilke, Roman E. Botcharnikov, Nobumichi Shimizu, Oliver Nebel, Camille Rivard, Dmitri A. Ionov

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    111 Citations (Scopus)

    Abstract

    Subduction zone magmas are more oxidised on eruption than those at mid-ocean ridges. This is attributed either to oxidising components, derived from subducted lithosphere (slab) and added to the mantle wedge, or to oxidation processes occurring during magma ascent via differentiation. Here we provide direct evidence for contributions of oxidising slab agents to melts trapped in the sub-arc mantle. Measurements of sulfur (S) valence state in sub-arc mantle peridotites identify sulfate, both as crystalline anhydrite (CaSO4) and dissolved SO4 2− in spinel-hosted glass (formerly melt) inclusions. Copper-rich sulfide precipitates in the inclusions and increased Fe3+/∑Fe in spinel record a S6+–Fe2+ redox coupling during melt percolation through the sub-arc mantle. Sulfate-rich glass inclusions exhibit high U/Th, Pb/Ce, Sr/Nd and δ34S (+ 7 to + 11‰), indicating the involvement of dehydration products of serpentinised slab rocks in their parental melt sources. These observations provide a link between liberated slab components and oxidised arc magmas.

    Original languageEnglish
    Article number3500
    JournalNature Communications
    Volume9
    Issue number1
    DOIs
    Publication statusPublished - 1 Dec 2018

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