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.

马里亚纳岛弧形构造的锶、钕、铅、氢同位素演化火山弧是一种复杂的混合体，由先前存在的地壳基底、俯冲板和邻近的地幔储集层产生。尽管弧形岩浆外流(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藏的长期变化联系在一起，但它们如何随着俯冲动力学(地壳厚度、板片倾角、会聚速度等)而变化仍不清楚。该项目旨在研究西北太平洋马里亚纳弧岩浆外流变化的原因。马里亚纳弧/弧后系统是大约4900万年前开始的大洋内伊豆-博宁-马里亚纳(IBM)弧的一部分。它以随时间以与长期地质变化相匹配的速率变化的K2O丰度而闻名。为了了解是什么驱使了马里亚纳的这种波动，有人提议测定马里亚纳火山岩从中渐新世到最近的化学变化。这一岩石记录是由海洋沉积物中的特弗拉沉积保存的，具有高时间精度和分辨率(~1 Ma)。虽然早期(~32-48 Ma)和现今(1 Ma)的熔岩提供了一个基本的框架，但只有熔岩提供了关于弧演化关键中期的全面信息。来自35_m组分的新鲜火山颗粒(玻璃、斯科石、浮石、幼年岩屑)将从最小变化的火山灰岩层中分离出来，并将分析这些样品的锶-钕-铅-氢同位素比值以及新鲜火山玻璃和颗粒的常量和微量元素。该项目涉及俯冲工厂倡议的一个基础科学主题：“汇聚速度和上盘厚度等强迫作用如何调节俯冲工厂的岩浆和流体的产生？”在地区范围内，新数据将填补IBM系统整体演变中的一个重要空白，这将为IBM融合边际的演变提供新的视角。在全球范围内，对长期弧演化的研究将有助于理解地球上的储集层是如何相互作用的，以及这种相互作用如何与弧岩浆通量和全球环境变化联系在一起。该项目将促进美国和澳大利亚科学家之间的科学合作。将进一步加强对地球科学界妇女的支持。施特劳布是一名残疾女研究员，她已经为IBM的进化做出了实质性贡献，这是她长期研究目标的一部分。Straub将制作一节在线边际迷你课程，分享她将teparas用作岩石成因工具的专业知识。计划让本科生参与这个项目的研究。