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

William Hutchison, Ranier Babiel, Adrian A. Finch, Michael Marks, Gregor Markl, Adrian J. Boyce, Eva Elisabeth Stüeken, Henrik Friis, Anouk M. Borst, Nicola J. Horsburgh

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7 Citations (Scopus)
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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 (δ34S of +1 to +5‰) can be reconstructed. A global δ34S 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.
Original languageEnglish
Article number4208
Number of pages12
JournalNature Communications
Volume10
DOIs
Publication statusPublished - 16 Sept 2019

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