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Updated: Aug 5, 2026

Preparation of Authigenic Pyrite from Methane-bearing Sediments for In Situ Sulfur Isotope Analysis Using SIMS
Published on: August 31, 2017
The sulfur content and isotopic composition of the subarc mantle
Zoltán Taracsák1,2, Tamsin A Mather2, Terry Plank3
1Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK.
Abstract:
Sulfur plays a critical role in modulating redox cycling on Earth. Yet, sulfur's behavior during subduction and in mantle redox reactions is debated. We analyzed 34S/32S in mafic arc melt inclusions from contrasting subduction zones and modeled slab-mantle interaction to investigate the subduction zone sulfur cycle. We find that degassing may enrich or deplete the melt strongly in 34S as a function of melt redox state. After correction for this effect, arc magmas have a substantially narrow range of δ34S values (+3 ± 2‰), higher than the ambient upper mantle (-1‰). Slab-derived sulfur is oxidized, evidenced by a concurrent increase in mantle Fe3+ and sulfur contents, and contributes up to 86% of the mantle wedge's sulfur budget. Arc magma δ34S values reflect a common slab source for sulfur: the oceanic crust. Subduction zones act as a "filter" for oxidative power and 34S, effectively returning these to the surface over geological timescales.
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