Uncovering and quantifying the subduction zone sulfur cycle from the slab perspective.,Nature Communications

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Uncovering and quantifying the subduction zone sulfur cycle from the slab perspective.
Nature Communications ( IF 14.7 ) Pub Date : 2020-01-24 , DOI: 10.1038/s41467-019-14110-4
Ji-Lei Li _{1,

2,

3} , Esther M Schwarzenbach ₄ , Timm John ₄ , Jay J Ague ₃ , Fang Huang ₅ , Jun Gao _{1,

2,

6} , Reiner Klemd ₇ , Martin J Whitehouse ₈ , Xin-Shui Wang _{1,

2}

Affiliation

Sulfur belongs among H2O, CO2, and Cl as one of the key volatiles in Earth's chemical cycles. High oxygen fugacity, sulfur concentration, and δ34S values in volcanic arc rocks have been attributed to significant sulfate addition by slab fluids. However, sulfur speciation, flux, and isotope composition in slab-dehydrated fluids remain unclear. Here, we use high-pressure rocks and enclosed veins to provide direct constraints on subduction zone sulfur recycling for a typical oceanic lithosphere. Textural and thermodynamic evidence indicates the predominance of reduced sulfur species in slab fluids; those derived from metasediments, altered oceanic crust, and serpentinite have δ34S values of approximately -8‰, -1‰, and +8‰, respectively. Mass-balance calculations demonstrate that 6.4% (up to 20% maximum) of total subducted sulfur is released between 30-230 km depth, and the predominant sulfur loss takes place at 70-100 km with a net δ34S composition of -2.5 ± 3‰. We conclude that modest slab-to-wedge sulfur transport occurs, but that slab-derived fluids provide negligible sulfate to oxidize the sub-arc mantle and cannot deliver 34S-enriched sulfur to produce the positive δ34S signature in arc settings. Most sulfur has negative δ34S and is subducted into the deep mantle, which could cause a long-term increase in the δ34S of Earth surface reservoirs.

中文翻译：

从平板的角度揭示和量化俯冲带的硫循环。

硫属于H2O，CO2和Cl，是地球化学循环中的关键挥发物之一。火山弧岩中高的氧气逸度，硫浓度和δ34S值归因于平板流体大量添加了硫酸盐。然而，平板状脱水流体中的硫形态，通量和同位素组成仍不清楚。在这里，我们使用高压岩石和封闭的脉络来为典型海洋岩石圈的俯冲带硫再循环提供直接约束。质地和热力学证据表明，平板流体中的硫种类减少。由变质沉积，蚀变的大洋地壳和蛇纹岩衍生的δ34S值分别约为-8‰，-1‰和+ 8‰。质量平衡计算表明6。在30-230 km深度之间释放了4％（最多20％）的总俯冲硫，并且主要的硫损失发生在70-100 km处，净δ34S组成为-2.5±3‰。我们得出的结论是，发生了从平板到楔形的适度硫迁移，但是源自平板的流体提供的硫酸盐微不足道，无法氧化弧下地幔，并且无法输送富含34S的硫在电弧环境中产生正δ34S签名。大多数硫具有负的δ34S并被俯冲到深层地幔中，这可能导致地表储层的δ34S长期增加。但是板坯衍生的流体只能提供微不足道的硫酸盐来氧化亚弧幔，而不能输送富含34S的硫，从而在电弧环境下不能产生正的δ34S签名。大多数硫具有负的δ34S并被俯冲到深层地幔中，这可能导致地表储层的δ34S长期增加。但是板坯衍生的流体只能提供微不足道的硫酸盐来氧化亚弧幔，而不能输送富含34S的硫，从而在电弧环境下不能产生正的δ34S签名。大多数硫具有负的δ34S并被俯冲到深层地幔中，这可能导致地表储层的δ34S长期增加。

更新日期：2020-01-24

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