The sulfur content and isotopic composition of the subarc mantle.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 42536727.
- Also identified by DOI 10.1126/sciadv.aeb9747 and PMC identifier 13426414.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Sulfur plays a critical role in modulating redox cycling on Earth. Yet, sulfur's behavior during subduction and in mantle redox reactions is debated. We analyzed <sup>34</sup>S/<sup>32</sup>S in mafic arc melt inclusions from contrasting subduction zones and modeled slab-mantle interaction to investigate the subduction zone sulfur cycle. We find that degassing may enrich or deplete the melt strongly in <sup>34</sup>S as a function of melt redox state. After correction for this effect, arc magmas have a substantially narrow range of δ<sup>34</sup>S values (+3 ± 2‰), higher than the ambient upper mantle (-1‰). Slab-derived sulfur is oxidized, evidenced by a concurrent increase in mantle Fe<sup>3+</sup> and sulfur contents, and contributes up to 86% of the mantle wedge's sulfur budget. Arc magma δ<sup>34</sup>S values reflect a common slab source for sulfur: the oceanic crust. Subduction zones act as a "filter" for oxidative power and <sup>34</sup>S, effectively returning these to the surface over geological timescales.