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Uncovering and quantifying the subduction zone sulfur cycle from the slab perspective.
- Source :
-
Nature communications [Nat Commun] 2020 Jan 24; Vol. 11 (1), pp. 514. Date of Electronic Publication: 2020 Jan 24. - Publication Year :
- 2020
-
Abstract
- Sulfur belongs among H <subscript>2</subscript> O, CO <subscript>2</subscript> , and Cl as one of the key volatiles in Earth's chemical cycles. High oxygen fugacity, sulfur concentration, and δ <superscript>34</superscript> S values in volcanic arc rocks have been attributed to significant sulfate addition by slab fluids. However, sulfur speciation, flux, and isotope composition in slab-dehydrated fluids remain unclear. Here, we use high-pressure rocks and enclosed veins to provide direct constraints on subduction zone sulfur recycling for a typical oceanic lithosphere. Textural and thermodynamic evidence indicates the predominance of reduced sulfur species in slab fluids; those derived from metasediments, altered oceanic crust, and serpentinite have δ <superscript>34</superscript> S values of approximately -8‰, -1‰, and +8‰, respectively. Mass-balance calculations demonstrate that 6.4% (up to 20% maximum) of total subducted sulfur is released between 30-230 km depth, and the predominant sulfur loss takes place at 70-100 km with a net δ <superscript>34</superscript> S composition of -2.5 ± 3‰. We conclude that modest slab-to-wedge sulfur transport occurs, but that slab-derived fluids provide negligible sulfate to oxidize the sub-arc mantle and cannot deliver <superscript>34</superscript> S-enriched sulfur to produce the positive δ <superscript>34</superscript> S signature in arc settings. Most sulfur has negative δ <superscript>34</superscript> S and is subducted into the deep mantle, which could cause a long-term increase in the δ <superscript>34</superscript> S of Earth surface reservoirs.
Details
- Language :
- English
- ISSN :
- 2041-1723
- Volume :
- 11
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Nature communications
- Publication Type :
- Academic Journal
- Accession number :
- 31980597
- Full Text :
- https://doi.org/10.1038/s41467-019-14110-4