Seawater-derived noble gases and halogens preserved in exhumed mantle wedge peridotite
Seawater-derived noble gases and halogens preserved in exhumed mantle wedge peridotite
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DOI：
10.1016/j.epsl.2010.03.029
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发表时间：
2010-05
影响因子：
5.3
通讯作者：
H. Sumino;R. Burgess;T. Mizukami;S. Wallis;G. Holland;C. Ballentine
中科院分区：
文献类型：
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作者：
H. Sumino;R. Burgess;T. Mizukami;S. Wallis;G. Holland;C. Ballentine
在这里，我们展示了如何东赤石橄榄岩体在三坝川变质带，前地幔楔的欧亚板块边缘的一个条子，已折返俯冲流体惰性气体和卤素与海洋孔隙流体签名从深度为100公里。以往的研究仅认为水通过蚀变洋壳和沉积物中的水化矿物分解而俯冲到地幔楔中。所观察到的稀有气体和卤素成分与海洋孔隙流体的惊人相似性要求海洋孔隙流体的俯冲和封闭系统保留至少100公里。东赤石橄榄岩似乎已经冻结，并保存了以前看不见的一部分深水循环过程，需要重新评估的主导运输机制和俯冲带的水源。事实上，一小部分的海洋孔隙流体，保存在下行含水橄榄岩，可以占主导地位的重惰性气体同位素和元素组成观察到的对流地幔。
Here we show how the Higashi-akaishi peridotite body in the Sanbagawa metamorphic belt, a sliver of the former mantle wedge of the eastern Eurasian plate margin, has exhumed subduction fluid noble gases and halogens with a marine pore-fluid signature from a depth of ∼100km. Previous work has only considered that water subduction into the mantle wedge occurs via decomposition of hydrated minerals in altered oceanic crust and sediment. The striking similarities of the observed noble gas and halogen compositions with marine pore fluids require subduction and closed system retention of marine pore fluid to at least 100km. The Higashi-akaishi peridotites appear to have frozen-in and preserved a previously unseen part of the deep water recycling process, requiring a reassessment of the dominant transport mechanism and source of water in subduction zones. Indeed, a small proportion of marine pore fluid, preserved in the downgoing hydrous peridotite, can account for the dominant heavy noble gas isotopic and elemental composition observed in the convecting mantle.