Sub-arc mantle oxidation is often attributed to sulfates from seawater transported in aqueous fluids derived from slab dehydration, but sulfur speciation and origin(s) in high-pressure fluids remain weakly constrained. Here, we use the four sulfur stable isotopes (S, S, S, S) to decipher processes, e.g. mixing of two end-member reservoirs and open-system reaction occurring during sulfur devolatilization, and deduce the nature and origin of sulfur species in aqueous slab-derived fluids. We analyzed high pressure metamorphic rocks from the Monviso massif Lower Shear Zone (LSZ; Western Alps), recording evidence of an interface-parallel, channelized fluid flow near peak burial metamorphic conditions (∼550 °C and 2.7 GPa). We sampled variably metasomatized Fe-Ti metagabbros, hybrid (talc) schists and serpentinites containing sulfides supposed to preserve the aqueous fluid composition, as well as other alpine metagabbro, metabasalt and serpentinites from greenschist to eclogite-facies devoid of the studied metasomatic overprint.

中文翻译：

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多种硫同位素证明富含硫酸盐的流体在深部板片内传输


弧下地幔氧化通常归因于板片脱水产生的水性流体中传输的海水中的硫酸盐，但高压流体中的硫形态和起源仍然受到较弱的限制。在这里，我们使用四种硫稳定同位素（S、S、S、S）来破译过程，例如两个端元储层的混合和硫脱挥发分过程中发生的开放系统反应，并推断出水性板片衍生流体中硫物质的性质和来源。我们分析了蒙维索地块下剪切带（LSZ；西阿尔卑斯山）的高压变质岩，记录了接近峰值埋藏变质条件（约 550 °C 和 2.7 GPa）的界面平行、通道化流体流动的证据。我们对不同交代的铁钛变辉长岩、混合（滑石）片岩和蛇纹岩进行了取样，这些硫化物被认为可以保留水性流体成分，以及其他高山变辉长岩、变玄武岩和蛇纹岩，从绿片岩到榴辉岩相，没有所研究的交代叠印。