Regional‐scale input of dispersed and discrete volcanic ash to the Izu‐Bonin and Mariana subduction zones
Regional‐scale input of dispersed and discrete volcanic ash to the Izu‐Bonin and Mariana subduction zones
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DOI：
10.1002/2014gc005561
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发表时间：
2014-11
期刊：
影响因子：
3.7
通讯作者：
R. Scudder;R. Murray;J. Schindlbeck;S. Kutterolf;F. Hauff;C. McKinley
中科院分区：
文献类型：
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作者：
R. Scudder;R. Murray;J. Schindlbeck;S. Kutterolf;F. Hauff;C. McKinley
我们对大洋钻探项目1149号站点（伊豆-小笠原弧）和深海钻探项目52号站点（马里亚纳弧）的大量海洋沉积物和火山灰层进行了地球化学和统计学表征，并量化了多个分散的火山灰源，它们共同构成了进入伊豆-小笠原-马里亚纳俯冲系统的半远洋沉积物质量的30-35%。多元统计分析表明，散装沉积物在站点1149是中国黄土，第二个成分不同的风成源，分散的镁铁质灰，分散的长英质灰的混合物。我们解释这些灰烬的来源，分别是来自伊豆-小笠原前弧（IBFA）的玄武岩和来自本州弧的流纹岩。大量沉积物的Sr-、Nd-和Pb同位素分析与基于化学/统计的解释一致。离散灰层参数（厚度，沉积速率和层数）的分散灰成分的质量积累率的比较表明，喷发频率，而不是喷发的大小，驱动分散灰记录。在52号站点，地球化学和统计建模表明，中国黄土、IBFA、分散的BNN（来自伊豆-小笠原的玻安岩）和来源不明的分散的长英质火山灰是来源。在1149号现场，灰层和分散灰在成分上是耦合的，而在52号现场，它们是分离的，因为没有玻安体层，但玻安体分散在沉积物中。火山和风成输入随时间的变化表明强烈的弧相关和气候相关的控制。
We have geochemically and statistically characterized bulk marine sediment and ash layers at Ocean Drilling Program Site 1149 (Izu‐Bonin Arc) and Deep Sea Drilling Project Site 52 (Mariana Arc), and have quantified that multiple dispersed ash sources collectively comprise ∼30–35% of the hemipelagic sediment mass entering the Izu‐Bonin‐Mariana subduction system. Multivariate statistical analyses indicate that the bulk sediment at Site 1149 is a mixture of Chinese Loess, a second compositionally distinct eolian source, a dispersed mafic ash, and a dispersed felsic ash. We interpret the source of these ashes as, respectively, being basalt from the Izu‐Bonin Front Arc (IBFA) and rhyolite from the Honshu Arc. Sr‐, Nd‐, and Pb isotopic analyses of the bulk sediment are consistent with the chemical/statistical‐based interpretations. Comparison of the mass accumulation rate of the dispersed ash component to discrete ash layer parameters (thickness, sedimentation rate, and number of layers) suggests that eruption frequency, rather than eruption size, drives the dispersed ash record. At Site 52, the geochemistry and statistical modeling indicates that Chinese Loess, IBFA, dispersed BNN (boninite from Izu‐Bonin), and a dispersed felsic ash of unknown origin are the sources. At Site 1149, the ash layers and the dispersed ash are compositionally coupled, whereas at Site 52 they are decoupled in that there are no boninite layers, yet boninite is dispersed within the sediment. Changes in the volcanic and eolian inputs through time indicate strong arc‐related and climate‐related controls.