Redox transfer at subduction zones: insights from Fe isotopes in the Mariana forearc
Redox transfer at subduction zones: insights from Fe isotopes in the Mariana forearc
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DOI：
10.7185/geochemlet.2003
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发表时间：
2020-01-31
影响因子：
4.9
通讯作者：
Williams, H. M.
中科院分区：
文献类型：
--
作者：
Debret, B.;Reekie, C. D. J.;Williams, H. M.
俯冲带是地球表面和内部深处之间化学交换的活跃场所，在调节行星的可居住性方面发挥着根本作用。然而，氧化还原敏感元件（例如，铁、碳和硫）在俯冲过程中的循环仍不清楚。在这里，我们使用铁稳定同位素（δ Fe-56），这是敏感的氧化还原相关的过程，研究弧前蛇纹岩碎屑从深海钻探泥火山形成以上的马里亚纳俯冲带在西太平洋。我们表明，蛇纹岩的弧前板衍生流体产生显着的三角洲Fe-56的变化。蛇纹岩体δ Fe-56、流体活动元素浓度（例如，B，As）和Fe ~（3+）/σ Fe的比值表明地幔楔的氧化作用是通过板片流体转移同位素轻铁实现的。这一过程必须反映的转移，无论是硫酸盐或碳酸盐轴承流体，优先复杂的同位素轻铁。
Subduction zones are active sites of chemical exchange between the Earth's surface and deep interior and play a fundamental role in regulating planet habitability. However, the mechanisms by which redox sensitive elements (e.g., iron, carbon and sulfur) are cycled during subduction remains unclear. Here we use Fe stable isotopes (delta Fe-56), which are sensitive to redox-related processes, to examine forearc serpentinite clasts recovered from deep sea drilling of mud volcanoes formed above the Mariana subduction zone in the Western Pacific. We show that serpentinisation of the forearc by slab-derived fluids produces dramatic delta Fe-56 variation. Unexpected negative correlations between serpentinite bulk delta Fe-56, fluid-mobile element concentrations (e.g., B, As) and Fe3+/Sigma Fe suggest a concomitant oxidation of the mantle wedge through the transfer of isotopically light iron by slab-derived fluids. This process must reflect the transfer of either sulfate- or carbonate-bearing fluids that preferentially complex isotopically light Fe.