No significant boron in the hydrated mantle of most subducting slabs

Andrew McCaig, Sofya Titarenko, Ivan Savov, Robert Cliff, David Banks, Adrian Boyce, Samuele Agostini

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


Boron has become the principle proxy for the release of seawater-derived fluids into arc volcanics, linked to cross-arc variations in boron content and isotopic ratio. Because all ocean floor serpentinites so far analysed are strongly enriched in boron, it is generally assumed that if the uppermost slab mantle is hydrated, it will also be enriched in boron. Here we present the first measurements of boron and boron isotopes in fast-spread oceanic gabbros in the Pacific, showing strong take-up of seawater-derived boron during alteration. We show that in one-pass hydration of the upper mantle, as proposed for bend fault serpentinisation, boron will not reach the hydrated slab mantle. Only prolonged hydrothermal circulation, for example in a long-lived transform fault, can add significant boron to the slab mantle. We conclude that hydrated mantle in subducting slabs will only rarely contribute to boron enrichment in arc volcanics, or to deep mantle recycling.
Original languageEnglish
Article number4602
Pages (from-to)1-10
Number of pages10
JournalNature Communications
Early online date2 Nov 2018
Publication statusPublished - 1 Dec 2018
Externally publishedYes


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