A record of spontaneous subduction initiation in the Izu-Bonin-Mariana arc
A record of spontaneous subduction initiation in the Izu-Bonin-Mariana arc
复制标题
DOI：
10.1038/ngeo2515
复制
发表时间：
2015-09-01
影响因子：
18.3
通讯作者：
Zhang, Zhaohui
中科院分区：
文献类型：
--
作者：
Arculus, Richard J.;Ishizuka, Osamu;Zhang, Zhaohui
构造板块向地幔俯冲的起始过程还知之甚少。如果俯冲是由遥远的洋中脊的推力或俯冲板片的拉力引起的，我们预计上覆板块会受到压缩和抬升。相反，致密岩石圈沿着与浮力岩石圈相邻的断层下沉而引起的自发俯冲则会导致伸展和岩浆作用。俯冲开始的岩石记录通常被较年轻的沉积物所掩盖，因此评估这些可能性被证明是难以捉摸的。本文分析了菲律宾海西北部奄美三卡库盆地火成岩基底岩和上覆沉积物的地球化学特征。最上层的基底岩石分布广泛，并通过岩墙提供。它们在成分和年龄上与邻近伊豆-小笠原-马里亚纳弧前的52-48百万年玄武岩相似，这受到上覆沉积物生物地层学的限制。基底熔岩的地球化学特征表明，俯冲岩石圈的一个组成部分参与了它们的成因，和熔岩来自地幔源岩的熔融亏损比那些在洋中脊。我们建议，在伊豆-小笠原-马里亚纳俯冲开始时形成的基底熔岩的模式与俯冲的自发启动一致。
The initiation of tectonic plate subduction into the mantle is poorly understood. If subduction is induced by the push of a distant mid-ocean ridge or subducted slab pull, we expect compression and uplift of the overriding plate. In contrast, spontaneous subduction initiation, driven by subsidence of dense lithosphere along faults adjacent to buoyant lithosphere, would result in extension and magmatism. The rock record of subduction initiation is typically obscured by younger deposits, so evaluating these possibilities has proved elusive. Here we analyse the geochemical characteristics of igneous basement rocks and overlying sediments, sampled from the Amami Sankaku Basin in the northwest Philippine Sea. The uppermost basement rocks are areally widespread and supplied via dykes. They are similar in composition and age-as constrained by the biostratigraphy of the overlying sediments-to the 52-48-million-year-old basalts in the adjacent Izu-Bonin-Mariana fore-arc. The geochemical characteristics of the basement lavas indicate that a component of subducted lithosphere was involved in their genesis, and the lavas were derived from mantle source rocks that were more melt-depleted than those tapped at mid-ocean ridges. We propose that the basement lavas formed during the inception of Izu-Bonin-Mariana subduction in a mode consistent with the spontaneous initiation of subduction.