Sulphur isotopes of alkaline magmas unlock long-term records of crustal recycling on Earth

• Published in: Nature Communications
• Main Authors: Hutchison, William, Babiel, Rainer J., Finch, Adrian A., Marks, Michael A. W., Markl, Gregor, Boyce, Adrian J., Stüeken, Eva E., Friis, Henrik, Borst, Anouk M., Horsburgh, Nicola J.
• Other Authors: EC | Horizon 2020 Framework Programme, RCUK | Natural Environment Research Council, Deutsche Forschungsgemeinschaft
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Science and Business Media LLC 2019
• Subjects: General Physics and Astronomy; General Biochemistry, Genetics and Molecular Biology; General Chemistry; Greenland
• Online Access: http://dx.doi.org/10.1038/s41467-019-12218-1; http://www.nature.com/articles/s41467-019-12218-1.pdf; http://www.nature.com/articles/s41467-019-12218-1

Abstract Earth’s surface and mantle sulphur reservoirs are connected via subduction, crustal recycling and volcanism. Although oceanic hotspot lavas currently provide the best constraints on the deep sulphur cycle, their restricted age range (<200 Ma) means they cannot reveal temporal variations in crustal recycling over Earth history. Sulphur-rich alkaline magmas offer the solution because they are associated with recycled sources (i.e. metasomatized lithospheric mantle and plumes) and, crucially, are found throughout the geological record. Here, we present a detailed study of sulphur isotope fractionation in a Mesoproterozoic alkaline province in Greenland and demonstrate that an enriched subduction-influenced source (δ 34 S of +1 to +5 ‰) can be reconstructed. A global δ 34 S compilation reveals secular variation in alkaline magma sources which support changes in the composition of the lithospheric mantle and/or Ga timescales for deep crustal recycling. Thus, alkaline magmas represent a powerful yet underutilized repository for interrogating crustal recycling through geological time.