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首页> 外文期刊>Geochemistry, geophysics, geosystems >The behavior of iron and zinc stable isotopes accompanying the subduction of mafic oceanic crust: A case study from Western Alpine ophiolites
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The behavior of iron and zinc stable isotopes accompanying the subduction of mafic oceanic crust: A case study from Western Alpine ophiolites

机译：伴随着乳头海洋地壳俯冲的钢铁稳定同位素的行为：西方高山渗透素的案例研究

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Arc lavas display elevated Fe3+/sigma Fe ratios relative to MORB. One mechanism to explain this is the mobilization and transfer of oxidized or oxidizing components from the subducting slab to the mantle wedge. Here we use iron and zinc isotopes, which are fractionated upon complexation by sulfide, chloride, and carbonate ligands, to remark on the chemistry and oxidation state of fluids released during prograde metamorphism of subducted oceanic crust. We present data for metagabbros and metabasalts from the Chenaillet massif, Queyras complex, and the Zermatt-Saas ophiolite (Western European Alps), which have been metamorphosed at typical subduction zone P-T conditions and preserve their prograde metamorphic history. There is no systematic, detectable fractionation of either Fe or Zn isotopes across metamorphic facies, rather the isotope composition of the eclogites overlaps with published data for MORB. The lack of resolvable Fe isotope fractionation with increasing prograde metamorphism likely reflects the mass balance of the system, and in this scenario Fe mobility is not traceable with Fe isotopes. Given that Zn isotopes are fractionated by S-bearing and C-bearing fluids, this suggests that relatively small amounts of Zn are mobilized from the mafic lithologies in within these types of dehydration fluids. Conversely, metagabbros from the Queyras that are in proximity to metasediments display a significant Fe isotope fractionation. The covariation of Fe-56 of these samples with selected fluid mobile elements suggests the infiltration of sediment derived fluids with an isotopically light signature during subduction.
机译：Arc VALAS相对于MORB显示FE3 + / Sigma FE比率升高。解释这一点的一种机制是将氧化或氧化组分从桥面楔形到地幔楔的动员和转移。在这里，我们使用铁和锌同位素，其在硫化物，氯化物和碳酸盐配体络合后分级，以评论在底层海底的促进变质过程中释放的流体的化学和氧化状态。我们向Chenaillet Massif，Queyras Complex和Zermatt-Saas Ophiolite（西欧阿尔卑斯州）（西欧阿尔卑斯山）提供了Metagrabbros和Metabasalts的数据，这些郊区P-T条件是变质的，并保持了它们的促进变质历史。在变质相跨越多种Fe或Zn同位素没有系统，可检测的分馏，而是eMlogites的同位素组成与Morb的公开数据重叠。随着翼展变质的增加，缺乏可分解的Fe同位素分馏可能反映了系统的质量平衡，并且在这种情况下，Fe InsoTopes不可追溯。鉴于Zn同位素被S轴承和C轴承流体分馏，这表明相对少量的Zn被从这些类型的脱水流体中的MAFIC岩性流动。相反，来自Queyras的Metagbbros，其邻近化合物的Queyras显示出显着的Fe同位素分馏。使用选定的流体移动元件的这些样品的Fe-56的变焦表明沉积物在俯卧期间具有同位素光签名的沉积物衍生的流体。

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