Subducting serpentinites release reduced, not oxidized, aqueous fluids.
- Piccoli F University of Bern, Institute of Geological Sciences, Balzerstrasse 1+3, 3012, Bern, Switzerland. francesca.piccoli@geo.unibe.ch.
- Hermann J University of Bern, Institute of Geological Sciences, Balzerstrasse 1+3, 3012, Bern, Switzerland.
- Pettke T University of Bern, Institute of Geological Sciences, Balzerstrasse 1+3, 3012, Bern, Switzerland.
- Connolly JAD Department of Earth Science, Swiss Federal Institute of Technology, Zurich, Switzerland.
- Kempf ED University of Bern, Institute of Geological Sciences, Balzerstrasse 1+3, 3012, Bern, Switzerland.
- Vieira Duarte JF University of Bern, Institute of Geological Sciences, Balzerstrasse 1+3, 3012, Bern, Switzerland.
- 2019-12-22
Published in:
- Scientific reports. - 2019
English
The observation that primitive arc magmas are more oxidized than mid-ocean-ridge basalts has led to the paradigm that slab-derived fluids carry SO2 and CO2 that metasomatize and oxidize the sub-arc mantle wedge. We combine petrography and thermodynamic modelling to quantify the oxygen fugacity (fO2) and speciation of the fluids generated by serpentinite dehydration during subduction. Silicate-magnetite assemblages maintain fO2 conditions similar to the quartz-fayalite-magnetite (QFM) buffer at fore-arc conditions. Sulphides are stable under such conditions and aqueous fluids contain minor S. At sub-arc depth, dehydration occurs under more reducing conditions producing aqueous fluids carrying H2S. This finding brings into question current models in which serpentinite-derived fluids are the cause of oxidized arc magmatism and has major implications for the global volatile cycle, as well as for redox processes controlling subduction zone geodynamics.
- Language
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- English
- Open access status
- gold
- Identifiers
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- DOI 10.1038/s41598-019-55944-8
- PMID 31862932
- Persistent URL
- https://sonar.ch/global/documents/107078
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