Along-arc variation in water distribution in the uppermost mantle beneath Kyushu, Japan, as derived from receiver function analyses
Along-arc variation in water distribution in the uppermost mantle beneath Kyushu, Japan, as derived from receiver function analyses
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DOI：
10.1002/jgrb.50257
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发表时间：
2013-07-01
影响因子：
3.9
通讯作者：
Shibutani, Takuo
中科院分区：
文献类型：
--
作者：
Abe, Yuki;Ohkura, Takahiro;Shibutani, Takuo
我们使用专门针对高倾角不连续性开发的接收函数分析，研究了日本俯冲带九州最上地幔的地震速度不连续性。我们阐明了不连续性的区域变化，如大陆莫霍面、海洋莫霍面和菲律宾海板片的上边界。从这些不连续性的几何形状和S波速度的对比中，我们发现菲律宾海板片的洋壳速度较低，并且可能在九州南部以下70公里、九州中部以下80-90公里以及九州北部以下不到50公里处被水合。九州中部弧前地幔楔存在低速带，可能含有水合物质和游离流体，但北九州和南九州弧前地幔楔不存在低速带。在九州南部下方，板块脱水后的水可能会移动到弧后一侧并引起弧火山活动。在九州中部下方，板块脱水后的水可能会移动到弧前侧，导致火山活动和弧前地幔物质水化出现间隙。在九州北部下方，洋壳似乎并没有在地幔楔中输送大量的水。低速水合的弧前地幔在九州中部北部下方向陆地延伸，可能会产生部分受到板块衍生流体污染的火山岩。
We investigated the seismic velocity discontinuities in the uppermost mantle of Kyushu, a subduction zone in Japan, using receiver function analyses developed especially for discontinuities with high dipping angles. We elucidated the regional variation of discontinuities, as being the continental Moho, oceanic Moho, and upper boundary of the Philippine Sea slab. From the geometry of these discontinuities and contrast in S wave velocities, we discovered that the oceanic crust of the Philippine Sea slab has a low velocity and is possibly hydrated down to 70km beneath south Kyushu, 80-90km beneath central Kyushu, and less than 50km beneath north Kyushu. The fore-arc mantle wedge beneath central Kyushu has a low-velocity zone and possibly contains hydrated materials and free fluid but such a low-velocity zone does not exist in the fore-arc mantle wedge beneath north Kyushu and south Kyushu. Beneath south Kyushu, water dehydrated from the slab could move to the back-arc side and cause arc volcanism. Beneath central Kyushu, water dehydrated from the slab could move to the fore-arc side and cause a gap in volcanism and hydration of fore-arc mantle materials. Beneath north Kyushu, the oceanic crust does not appear to convey water abundantly in the mantle wedge. The low-velocity hydrated fore-arc mantle extends landward beneath the northern part of central Kyushu and could produce volcanic rocks partially contaminated by slab-derived fluid.