title: Zinc isotope evidence for sulfate-rich fluid transfer across subduction zones.
abstract: Subduction zones modulate the chemical evolution of the Earth's mantle. Water and volatile elements in the slab are released as fluids into the mantle wedge and this process is widely considered to result in the oxidation of the sub-arc mantle. However, the chemical composition and speciation of these fluids, which is critical for the mobility of economically important elements, remain poorly constrained. Sulfur has the potential to act both as oxidizing agent and transport medium. Here we use zinc stable isotopes (δ66Zn) in subducted Alpine serpentinites to decipher the chemical properties of slab-derived fluids. We show that the progressive decrease in δ66Zn with metamorphic grade is correlated with a decrease in sulfur content. As existing theoretical work predicts that Zn-SO42-complexes preferentially incorporate heavy δ66Zn, our results provide strong evidence for the release of oxidized, sulfate-rich, slab serpentinite-derived fluids to the mantle wedge.
authors.affiliation: Department of Earth Sciences, Cambridge University, Downing St, Cambridge CB2 3EQ, UK.|Department of Earth Sciences, Durham University, Elvet Hill, Durham DH1 3LE, UK.
authors.forename: Marie-Laure
authors.initials: ML
authors.lastname: Pons
authors.affiliation: Department of Earth Sciences, Cambridge University, Downing St, Cambridge CB2 3EQ, UK.|Department of Earth Sciences, Durham University, Elvet Hill, Durham DH1 3LE, UK.
authors.forename: Baptiste
authors.initials: B
authors.lastname: Debret
authors.affiliation: Department of Earth Sciences, Durham University, Elvet Hill, Durham DH1 3LE, UK.
authors.forename: Pierre
authors.initials: P
authors.lastname: Bouilhol
authors.affiliation: Université de Lyon, UJM-Saint-Etienne, Laboratoire Magmas et Volcans, UMR 6524, CNRS, UBP, IRD, F-42023 Saint-Etienne, France.
authors.forename: Adélie
authors.initials: A
authors.lastname: Delacour
authors.affiliation: Department of Earth Sciences, Cambridge University, Downing St, Cambridge CB2 3EQ, UK.|Department of Earth Sciences, Durham University, Elvet Hill, Durham DH1 3LE, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Williams