Slab-derived halogens and noble gases illuminate closed system processes controlling volatile element transport into the mantle wedge
Slab-derived halogens and noble gases illuminate closed system processes controlling volatile element transport into the mantle wedge
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板片衍生的卤素和稀有气体照亮了控制挥发性元素传输到地幔楔的封闭系统过程
DOI：
10.1016/j.epsl.2016.10.012
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发表时间：
2017
影响因子：
5.3
通讯作者：
Kobayashi M
中科院分区：
文献类型：
--
作者：
Kobayashi M
卤素和惰性气体系统是俯冲带挥发性再循环的有力示踪剂。本文研究了从两个对比俯冲带（堪察加弧的阿瓦查火山和吕宋弧的皮纳图博火山）的火山锋采集的含富氢流体包裹体的地幔橄榄岩的卤素和稀有气体组成，以及从一个橄榄岩地块（日本北海道的霍罗曼地块）采集的造山橄榄岩的卤素和稀有气体组成，该地块代表了地幔楔的一部分。目的是确定挥发性物质如何被带入地幔楔，以及俯冲流体如何改变地幔中的卤素和惰性气体成分。富氢流体中的卤素和稀有气体特征与海相沉积孔隙流体、弧前岩和海底蛇纹岩相似。这表明深海沉积物中的海洋孔隙流体由蛇纹岩携带并供给地幔楔，保留了其原有的卤素和惰性气体组成。研究认为，沉积孔隙流体源水在洋外隆起沿断裂的封闭体系中通过水化作用进入蛇纹岩，保留了沉积孔隙流体的Cl/H2O和36ar /H2O值。海洋岩石圈地幔内部的脱水-水合作用维持了封闭体系，直至蛇纹石脱水的最后阶段。在蛇纹石脱水最后阶段释放的流体中，沉积孔隙流体类卤素和稀有气体特征由于通道化程度高而得以保留，而原始的Cl/H2O和36ar /H2O比值则由于卤素和稀有气体在含水矿物中较高的不相容性而被分馏。
Halogen and noble gas systematics are powerful tracers of volatile recycling in subduction zones. We present halogen and noble gas compositions of mantle peridotites containing H2O-rich fluid inclusions collected at volcanic fronts from two contrasting subduction zones (the Avacha volcano of Kamchatka arc and the Pinatubo volcano of Luzon arcs) and orogenic peridotites from a peridotite massif (the Horoman massif, Hokkaido, Japan) which represents an exhumed portion of the mantle wedge. The aims are to determine how volatiles are carried into the mantle wedge and how the subducted fluids modify halogen and noble gas compositions in the mantle. The halogen and noble gas signatures in the H2O-rich fluids are similar to those of marine sedimentary pore fluids and forearc and seafloor serpentinites. This suggests that marine pore fluids in deep-sea sediments are carried by serpentine and supplied to the mantle wedge, preserving their original halogen and noble gas compositions. We suggest that the sedimentary pore fluid-derived water is incorporated into serpentine through hydration in a closed system along faults at the outer rise of the oceanic, preserving Cl/H2O and36Ar/H2O values of sedimentary pore fluids. Dehydration–hydration process within the oceanic lithospheric mantle maintains the closed system until the final stage of serpentine dehydration. The sedimentary pore fluid-like halogen and noble gas signatures in fluids released at the final stage of serpentine dehydration are preserved due to highly channelized flow, whereas the original Cl/H2O and36Ar/H2O ratios are fractionated by the higher incompatibility of halogens and noble gases in hydrous minerals.
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发表时间：
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期刊：
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影响因子：
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