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

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 provid...

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Bibliographic Details
Published in:Nature communications 2018-08, Vol.9 (1), p.3500-10, Article 3500
Main Authors: Bénard, Antoine, Klimm, Kevin, Woodland, Alan B., Arculus, Richard J., Wilke, Max, Botcharnikov, Roman E., Shimizu, Nobumichi, Nebel, Oliver, Rivard, Camille, Ionov, Dmitri A.
Format: Article
Language:English
Subjects:
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140/58
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704/2151/209
704/2151/431
Ascent
Dehydration
Devolatilization
Earth Sciences
Electric arc melting
Environmental Sciences
Geochemistry
Global Changes
Humanities and Social Sciences
Inclusions
Iron
Lava
Lithosphere
Magma
Mantle
Melts
Mid-ocean ridges
multidisciplinary
Oxidation
Percolation
Precipitates
Science
Science (multidisciplinary)
Sciences of the Universe
Spinel
Sulfates
Sulfides
Sulfur
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Summary: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 (CaSO 4 ) and dissolved SO 4 2− in spinel-hosted glass (formerly melt) inclusions. Copper-rich sulfide precipitates in the inclusions and increased Fe 3+ /∑Fe in spinel record a S 6+ –Fe 2+ redox coupling during melt percolation through the sub-arc mantle. Sulfate-rich glass inclusions exhibit high U/Th, Pb/Ce, Sr/Nd and δ 34 S (+ 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. The oxidised nature of arc magmas is either attributed to recycling from the slab or magma differentiation. Here, the authors show that oxidised iron and sulfur, respectively in sub-arc mantle spinel and glass inclusions with elevated U/Th, Pb/Ce, Sr/Nd and δ 34 S, trace dehydration products of slab serpentinites.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-018-05804-2