High-pressure dehydration of serpentinite during subduction generates fluids that flux and melt the overlying mantle wedge, forming primary arc basalts. These basalts are substantially more oxidized than their mid-ocean ridge counterparts. At the slab surface of current subduction zones, these deserpentinization fluids are intrinsically oxidized, but, owing to the low sulfur content of subducted serpentinite, they only result in a low mantle wedge oxidation rate, which cannot account for the oxidized source of arc basalts. Here we show that infiltration of sediment-derived fluids modulates and can drastically change the oxidation capacity of deserpentinization slab fluids. The modulation of the deserpentinization oxidation capacity mostly depends on the stability and abundance of dissolved oxidized aqueous species of redox-sensitive elements—notably sulfate—and not solely on the oxidation state of the sediment. Infiltration of CH₄-bearing fluids derived from graphite-bearing sediment reduces the intrinsically high oxidant capacity of deserpentinization fluids, explaining the relatively low fO₂ observed in natural metaperidotite. Infiltration of sulfate-CO₂-bearing, sediment-derived fluids—prevalent in modern subduction zones—generates deserpentinization fluids with a high oxidation capacity in cold and hot subduction zones, resulting in a global mantle wedge oxidation rate of 3.5 km³ yr⁻¹. Such slab fluids will oxidize the mantle wedge at a rate similar to that of arc-basalt generation and thus account for the oxidized nature of arc volcanism.

蛇纹岩在俯冲过程中的高压脱水产生的流体流动并熔化上覆的地幔楔，形成原生弧形玄武岩。这些玄武岩比它们在大洋中脊对应物的氧化程度要高得多。在当前俯冲带的板片表面，这些脱蛇纹石化流体本质上是氧化的，但由于俯冲蛇纹岩含硫量低，它们仅导致低的地幔楔氧化率，这不能解释弧形玄武岩的氧化来源。在这里，我们表明沉积物衍生流体的渗透调节并且可以显着改变脱蛇纹石板流体的氧化能力。脱蛇纹石氧化能力的调节主要取决于氧化还原敏感元素（尤其是硫酸盐）溶解的氧化水性物质的稳定性和丰度，而不仅仅是沉积物的氧化态。CH的渗透_{源自含石墨沉积物的含4}的流体降低了脱蛇纹石化流体固有的高氧化能力，这解释了在天然变橄榄岩中观察到的相对较低的f O _{2 。}现代俯冲带中普遍存在的含硫酸盐-CO ₂的沉积物衍生流体的渗透在冷和热俯冲带中产生具有高氧化能力的脱蛇纹石化流体，导致全球地幔楔氧化速率为 3.5 km ³  yr ⁻¹ . 这种板块流体将以类似于弧形玄武岩生成的速率氧化地幔楔，从而解释了弧形火山作用的氧化性质。