Boron isotope evidence for shallow fluid transfer across subduction zones by serpentinized mantle
Boron isotope evidence for shallow fluid transfer across subduction zones by serpentinized mantle
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DOI：
10.1130/g33233.1
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发表时间：
2012-10
期刊：
影响因子：
5.8
通讯作者：
M. Scambelluri;S. Tonarini
中科院分区：
文献类型：
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作者：
M. Scambelluri;S. Tonarini
由海洋和弧前地幔蚀变形成的蛇纹岩是弧岩浆作用的主要挥发性和流体流动元素储库，尽管它们在俯冲带挥发性循环中占主导地位的直接证据一直难以捉摸。硼同位素是俯冲过程中流体介导的传质的既定标记。改变的洋壳和沉积物已被证明在弧下地幔中释放出 11 B 贫化流体，这不能解释许多弧的 11 B 富集。与这些地壳储层相反，我们记录了俯冲带高山蛇纹岩中保留的高 δ 11 B 值。这些逐渐埋藏的岩石中不会发生 11 B 分馏：释放出的富含 11 B 的流体独特地解释了弧岩浆δ 11 B 的升高。 B、O-H 和 Sr 同位素系统表明，蛇纹石化是由俯冲历史早期渗透板片-地幔界面的板片流体驱动的。
Serpentinites formed by alteration of oceanic and forearc mantle are major volatile and fluid-mobile element reservoirs for arc magmatism, though direct proof of their dominance in the subduction-zone volatile cycles has been elusive. Boron isotopes are established markers of fluid-mediated mass transfer during subduction. Altered oceanic crust and sediments have been shown to release in the subarc mantle 11 B-depleted fluids, which cannot explain 11 B enrichment of many arcs. In contrast to these crustal reservoirs, we document high δ 11 B values retained in subduction-zone Alpine serpentinites. No 11 B fractionation occurs in these rocks with progressive burial: the released 11 B-rich fluids uniquely explain the elevated δ 11 B of arc magmas. B, O-H, and Sr isotope systems indicate that serpentinization was driven by slab fluids that infiltrated the slab-mantle interface early in the subduction history.