MARGINS: The Sr-Nd-Pb-Hf Isotope Evolution of the Mariana Island Arc

边缘：马里亚纳岛弧的 Sr-Nd-Pb-Hf 同位素演化

• 批准号: 0840848
• 负责人: Susanne Straub
• 金额: $ 23.25万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-04-15 至 2013-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0840848&HistoricalAwards=false
• 关键词: MARGINS; Sr; Nd; Pb; Hf

The Sr-Nd-Pb-Hf isotope evolution of the Mariana Island ArcIntellectual Merit. Volcanic arcs represent a complex blend produced from pre-existing crustal basement, subducting slab and adjacent mantle reservoirs. Although temporal variations in arc magmatic outfluxes (compositions and volumes) must somehow be coupled to secular changes of the Earth's surface and mantle reservoirs, it remains unclear how they vary with subduction dynamics (crustal thickness, slab dip, convergence rate etc.). This project aims to investigate the causes of the variable magmatic outflux of the Mariana arc in the NW Pacific. The Mariana arc/backarc system is part of the intra-oceanic Izu Bonin-Mariana (IBM) arc that initiated ~49 million years ago. It is well known for its variable K2O-enrichment over time at rates that match to secular geological change. To understand what forces such Mariana 'fluctuations', it is proposed to determine chemical variations in Mariana volcanic rocks from the mid-Oligocene to Recent time. This rock record is preserved by tephra deposits in the marine sediments with high temporal precision and resolution (~1 Ma). While the lavas of the early (~32-48 Ma) and present-day arc (1 Ma) provide an essential framework, only the tephras provide comprehensive information on the crucial intermediate period of arc evolution. Fresh volcanic particles (glasses, scoria, pumice, juvenile lithics) from the fraction 35 _m will be separated from minimally altered tephra layers, and these samples will be analyzed for Sr-Nd-Pb-Hf isotope ratios and major and trace elements of fresh volcanic glasses and particles.The project bears on one of the fundamental science themes of the Subduction Factory Initiative: 'How do forcing functions such as convergence rate and upper plate thickness regulate production of magma and fluid from the Subduction Factory?'. On a regional scale, the new data will fill an important gap in the overall evolution of the IBM system that will provide new perspectives on the evolution of the IBM convergent margin. On a global scale, the study of secular arc evolution will aid in the understanding how the Earth's reservoirs interact, and how this may be linked to arc magmatic fluxes and global environmental change.Broader Impacts. The project will promote scientific partnership between U.S. and Australian scientists. The support for women in the geosciences will be furthered. Straub is a female researcher with a disability who has already made substantial contributions to the IBM evolution as part of a long-held goal of her research. Straub will produce an online MARGINS mini-lesson to share her expertise on the use of tephras as petrogenetic tool. It is planned to involve undergraduate students in this project research.

马里亚纳岛弧的 Sr-Nd-Pb-Hf 同位素演化智力成果。火山弧代表了由预先存在的地壳基底、俯冲板片和邻近地幔储层产生的复杂混合物。尽管弧岩浆流出量（成分和体积）的时间变化必须以某种方式与地球表面和地幔储层的长期变化耦合，但仍不清楚它们如何随俯冲动力学（地壳厚度、板片倾角、收敛速度等）变化。该项目旨在调查西北太平洋马里亚纳岛弧岩浆流出量变化的原因。马里亚纳弧/弧后系统是大约 4900 万年前开始的洋内伊豆博宁-马里亚纳 (IBM) 弧的一部分。它以其随着时间的推移而变化的 K2O 富集度而闻名，其变化率与长期地质变化相匹配。为了了解马里亚纳“波动”的原因，建议确定马里亚纳火山岩从渐新世中期到近代的化学变化。该岩石记录由海洋沉积物中的火山灰沉积物保存，具有较高的时间精度和分辨率（~1 Ma）。虽然早期（约 32-48 Ma）和现今弧（1 Ma）的熔岩提供了一个重要的框架，但只有火山灰提供了有关弧演化关键中期的全面信息。来自 35 米部分的新鲜火山颗粒（玻璃、火山渣、浮石、幼岩）将从微小改变的火山灰层中分离出来，并对这些样本进行 Sr-Nd-Pb-Hf 同位素比以及新鲜火山玻璃和颗粒的主要和微量元素的分析。该项目与俯冲工厂计划的基本科学主题之一有关：“如何 诸如收敛速度和上板厚度之类的强迫函数调节着俯冲工厂的岩浆和流体的产生？”。在区域范围内，新数据将填补IBM系统整体演进中的一个重要空白，这将为IBM收敛余量的演进提供新的视角。在全球范围内，对长期弧演化的研究将有助于了解地球储层如何相互作用，以及这如何与弧岩浆通量和全球环境变化联系起来。更广泛的影响。该项目将促进美国和澳大利亚科学家之间的科学伙伴关系。将进一步加强对地球科学领域女性的支持。 Straub 是一位残疾女性研究员，作为她长期研究目标的一部分，她已经为 IBM 的发展做出了重大贡献。 Straub 将制作一门在线 MARGINS 迷你课程，分享她在使用火山灰作为岩石成因工具方面的专业知识。计划让本科生参与该项目研究。