Boron contents of Japan Trench sediments and Iwate basaltic lavas, Northeast Japan arc: estimation of sediment-derived fluid contribution in mantle wedge
Boron contents of Japan Trench sediments and Iwate basaltic lavas, Northeast Japan arc: estimation of sediment-derived fluid contribution in mantle wedge
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DOI：
10.1016/s0012-821x(01)00244-8
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发表时间：
2001-03
影响因子：
5.3
通讯作者：
T. Sano;T. Hasenaka;A. Shimaoka;C. Yonezawa;T. Fukuoka
中科院分区：
文献类型：
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作者：
T. Sano;T. Hasenaka;A. Shimaoka;C. Yonezawa;T. Fukuoka
日本东北弧下方的地幔楔包含了从下降板块的两个部分脱水的含水流体：沉积层和蚀变海洋地壳（AOC）。为了估计地幔楔体中沉积物衍生流体的重量百分比，我们测定了日本海沟沉积物和日本东北部火山锋岩手玄武熔岩的硼和其他元素含量。利用海沟沉积物的微量元素含量估算沉积源流体的微量元素含量，利用已有报道的AOC微量元素含量估算AOC源流体的微量元素含量。通过对两种板源流体和岩尾玄武熔岩的可动/不可动元素比值（B/Sm、Ba/Sm、K2O/Sm、B/Zr、Ba/Zr、K2O/Zr）的检测，表明在日本东北弧下地幔楔中，aoc源流体与沉积物源流体的混合比为90:10。活动/不活动元素比值还表明，俯冲沉积物以沉积流体而非沉积熔体的形式再循环到日本东北部的地幔楔。由于地幔楔中总板岩衍生流体的重量分数估计小于1 wt%，因此向地幔楔中添加少量（<0.1 wt%）的沉积物衍生流体可以满足岩手玄武熔岩中硼和其他微量元素的含量。
Mantle wedge below the Northeast Japan arc contains hydrous fluids that dehydrated from two parts of the descending slab: a sediment layer and an altered oceanic crust (AOC). In order to estimate the weight percent of a sediment-derived fluid in the mantle wedge, we determine boron and other element contents of Japan Trench sediments and Iwate basaltic lavas on the Northeast Japan volcanic front. Trace element contents of the trench sediments are used to estimate those of the sediment-derived fluid, and previously reported trace element contents of the AOC are used to estimate those of the AOC-derived fluid. Examination of mobile/immobile element ratios (B/Sm, Ba/Sm, K2O/Sm, B/Zr, Ba/Zr, K2O/Zr) of the two slab-derived fluids and Iwate basaltic lavas, indicates a mixing ratio between the AOC-derived fluid and the sediment-derived fluid is 90:10 in the mantle wedge beneath the Northeastern Japan arc. The mobile/immobile element ratios also suggest that the subducted sediment recycle to the mantle wedge beneath Northeast Japan as sediment-fluid rather than sediment-melt. Since the weight fraction of the total slab-derived fluid in the mantle wedge is estimated to be less than 1 wt%, an addition of a small amount (<0.1 wt%) of the sediment-derived fluid to the mantle wedge fulfills the boron and other trace element contents in the Iwate basaltic lavas.