Abstract Serpentinization occurs both within the seafloor, when seawater percolates through fractures to alter underlying peridotite, and in subduction zones, when aqueous fluids from the dehydration of the slab are released within the subduction channel. The main difference between these two environments is, therefore, the source of serpentinizing fluid. However, distinguishing between the various types of serpentinites encountered in suture zones is difficult, essentially because of the lack of significant differences in their mineralogy and major and trace element chemistry. Eight samples from Corsica and the Western Alps representing slab serpentinites (i.e., serpentinites embedded within the subducting slab, which are fragments of former abyssal serpentinites) and seven samples from Guatemala and Nicaragua representing mantle wedge serpentinites (i.e., serpentinites that form in situ above the subducting slab, by hydration of the overlying mantle wedge) have been selected to study their Fluid-Mobile Elements, REE concentrations, and boron (B) isotopic signatures. The trace element results do not allow a conclusion about the source of fluid(s), but the B isotopic signatures do permit identification of the different fluid sources responsible for the serpentinization. The δ11B values of slab serpentinites are significantly positive, ranging from +12 to +34‰, in the same range as present-day abyssal serpentinites (+5.5 to +40.5‰), which are altered by seawater. Therefore, these positive signatures indicate serpentinization by seawater-derived fluid. The B isotopic signature acquired during oceanic residency is therefore preserved even after subduction processes subjected the serpentinites to eclogite facies conditions. By contrast, δ11B in samples from the mantle wedge range from −14 to +10‰, supporting the interpretation of interactions with fluids derived from the progressive dehydration of the slab, which releases fluids with slightly positive and negative δ11B. It indicates that mantle wedge serpentinite isotopic signature is acquired via the infiltration of subducted crust-derived metamorphic fluids during the subduction processes.

中文翻译：

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俯冲带深部地幔蛇纹石化：从板片和地幔楔蛇纹岩中的原位B同位素洞察

摘要 蛇纹石化发生在海底（海水通过裂缝渗入改变下面的橄榄岩）和俯冲带（板片脱水产生的含水流体在俯冲通道内释放时）。因此，这两种环境之间的主要区别在于蛇纹石化流体的来源。然而，很难区分缝合带中遇到的各种类型的蛇纹石，主要是因为它们的矿物学以及主要和微量元素化学没有显着差异。来自科西嘉岛和西阿尔卑斯山的八个样品，代表板条蛇纹岩（即嵌入俯冲板片内的蛇纹石，它们是前深海蛇纹岩的碎片）和来自危地马拉和尼加拉瓜的七个代表地幔楔蛇纹岩的样品（即，通过上覆地幔楔的水合在俯冲板片上方原位形成的蛇纹石）已被选择来研究它们的流体流动元素、REE 浓度和硼 (B) 同位素特征。微量元素结果无法得出关于流体来源的结论，但 B 同位素特征确实允许识别导致蛇纹石化的不同流体来源。板条蛇纹岩的δ11B值显着为正，范围为+12～+34‰，与受海水蚀变的现今深海蛇纹岩（+5.5～+40.5‰）范围相同。因此，这些积极的特征表明海水衍生的流体蛇纹石化。因此，即使在俯冲过程使蛇纹岩经受榴辉岩相条件之后，在海洋居住期间获得的 B 同位素特征也得以保留。相比之下，地幔楔样品中的 δ11B 范围从 -14 到 +10‰，支持对来自板块逐渐脱水的流体相互作用的解释，这释放了具有轻微正负 δ11B 的流体。这表明地幔楔蛇纹岩同位素特征是通过俯冲过程中俯冲地壳衍生变质流体的渗透获得的。支持对来自板块逐渐脱水的流体相互作用的解释，这会释放出具有轻微正负 δ11B 的流体。这表明地幔楔蛇纹岩同位素特征是通过俯冲过程中俯冲地壳衍生变质流体的渗透获得的。支持对来自板块逐渐脱水的流体相互作用的解释，这会释放出具有轻微正负 δ11B 的流体。这表明地幔楔蛇纹岩同位素特征是通过俯冲过程中俯冲地壳衍生变质流体的渗透获得的。