Mantle transition zone structure beneath the Changbai volcano: Insight into deep slab dehydration and hot upwelling near the 410 km discontinuity
Mantle transition zone structure beneath the Changbai volcano: Insight into deep slab dehydration and hot upwelling near the 410 km discontinuity
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DOI：
10.1002/2016jb012959
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发表时间：
2016-08
期刊：
影响因子：
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通讯作者：
You Tian;Hongxiang Zhu;Dapeng Zhao;Cai Liu;Xuan Feng;T. Liu;Jincheng Ma
中科院分区：
文献类型：
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作者：
You Tian;Hongxiang Zhu;Dapeng Zhao;Cai Liu;Xuan Feng;T. Liu;Jincheng Ma
本文利用接收函数方法研究了中国东北长白板内活火山地幔过渡带的详细结构。利用共转换点叠加方法，得到了70个宽带台站记录的3005个多普勒接收函数。为了进行时间到深度的转换，我们使用研究区域的三维速度模型，以考虑结构非均匀性的影响。我们的研究结果揭示了显着的深度变化的410，520和660公里的不连续。在长白火山下方发现了410 km不连续面的宽凹陷和低速异常，这可能反映了在克拉珀龙正斜率的410 km不连续面周围有大规模的热地幔上涌。520 km的不连续面被清楚地识别出来，它的隆起发生在静止的太平洋板块之上。在660 km不连续面上还发现了一个显著的凹陷，它沿39°N-44°N范围内的深震群走向沿着拉长，凹陷区的横向范围约为400 km。由于520和660 km不连续面分别对应于正克拉珀龙斜坡和负克拉珀龙斜坡，因此我们认为520隆起和660凹陷是由冷俯冲太平洋板片引起的。太平洋板块的一部分可能已经渗透到下地幔中，因此在深震群前造成了大规模的660低压。我们的结果还揭示了俯冲太平洋板块的上边界的地幔过渡带的一部分。
We study the detailed mantle transition zone structure beneath the active Changbai intraplate volcano in Northeast China by using a receiver‐function method. A total of 3005 teleseismic receiver functions recorded by 70 broadband stations are obtained by using a common‐conversion‐point stacking method. For conducting the time‐to‐depth conversion, we use a three‐dimensional velocity model of the study region so as to take into account the influence of structural heterogeneities. Our results reveal significant depth variations of the 410, 520, and 660 km discontinuities. A broad depression of the 410 km discontinuity and a low‐velocity anomaly are revealed beneath the Changbai volcano, which may reflect a large‐scale hot mantle upwelling around the 410 km discontinuity with a positive Clapeyron slope. The 520 km discontinuity is identified clearly, and its uplift occurs above the stagnant Pacific slab. We also find a prominent depression of the 660 km discontinuity, which is elongated along the trend of deep earthquake clusters in a range of 39°N–44°N latitude, and the depression area has a lateral extent of about 400 km. Because the 520 and 660 km discontinuities correspond to positive and negative Clapeyron slopes, respectively, we think that the 520 uplift and the 660 depression are caused by the cold subducting Pacific slab. A part of the Pacific slab may have penetrated into the lower mantle and so caused the large‐scale 660 depression in front of the deep earthquake clusters. Our results also reveal a part of the upper boundary of the subducting Pacific slab in the mantle transition zone.