Temporal/spatial scales of mantle wedge composition and processes investigated with young boninites and basalts from the unusually active NE Lau Basin

用来自异常活跃的NE Lau盆地的年轻桠岩和玄武岩研究地幔楔成分和过程的时空尺度

• 批准号: 1538121
• 负责人: Kenna Rubin
• 金额: $ 27.54万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-15 至 2020-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1538121&HistoricalAwards=false
• 关键词: Temporal; spatial; scales; mantle; wedge

This project is a study of subduction zone volcanic rocks to understand how they form. Subduction zones are places where materials from Earth's surface (sediments, volcanic rocks, and other rocky materials) are returned to the mantle. During this process fluids are drawn from the "slab" of subducting material while it descends, causing the overlying mantle to melt, producing magmas that drive a significant portion of Earth's volcanism. Despite 50 years of research about how and where this magmatic activity occurs, the range of volcanic styles and products, and their contributions to human society (hazards, ore formation, landscape evolution, etc.), numerous questions remain about the conditions and timescales of melting in the mantle, the different types of rocks that might melt, and the sizes and shapes of these different subterranean rock regions. In addition scientists still have a very incomplete picture of how all of these things contribute to what type of magma is ultimately erupted and what style the eruptions take (for example, how big, how frequent, how explosive). This research project addresses these questions using recently erupted, rare, volcanic rocks called boninites. These rocks form when H2O is added to the shallow mantle under very high temperature conditions. The tools of geochemistry, isotope geochemistry, and naturally-occurring radioactive element distributions in these rocks will be used to analyze an already existing, unique, set of samples. Project goals are to determine: (1) the variety and spatial scale of mantle compositions beneath this subduction zone, (2) the timescales over which they melt, (3) how magma forms and migrates to the surface, and (4) how this contributes to volcanic activity. Answers to these questions have broader impacts to society and the national interest because they provide information on processes leading to magmatism and volcanism (and associated hazards and benefits) at subduction zones, which occur both off the western coast of the United States and along the coasts of many of our partner nations in the Americas, Caribbean and Pacific Rim, like Japan, Taiwan and New Zealand. In addition, the project will fund an institution in an EPSCoR state (Hawaii), support an early career researcher, and carry out public outreach through the NOAA outreach engine and U Hawaii websites. This project will study interoceanic subduction zone volcanism, using a unique set of young boninite and related mafic/ultramafic samples from the nine Mata Volcanoes and neighboring rear arc and back arc volcanoes (Northeast Lau and Fonualei Spreading Centers). U-series disequilibria and analyses of Sr-Nd-Pb-Hf isotopes, and major/trace element abundances in already-collected volcanic glasses, minerals and whole rocks will be used to investigate high resolution (km-scale) mantle wedge heterogeneity at an active inter-oceanic arc/backarc, sub-millennial variations in subduction fluid inputs, and conditions of boninite and other magma petrogenesis. Hypotheses will be tested to address how fluids from the subducting slab induce melting in the overlying mantle, how different compositions of mantle melt, how different magmas are delivered to the surface in a way that preserves large variations in magma composition over small spatial scales, and the timescales of these various processes, which prelimimary data indicates is likely to be much faster in some cases than heretofore realized.

这个项目是研究俯冲带火山岩，以了解它们是如何形成的。俯冲带是地球表面的物质（沉积物，火山岩和其他岩石物质）返回地幔的地方。在这个过程中，流体从俯冲物质的“板”中被抽取出来，导致上覆的地幔熔化，产生驱动地球火山活动的重要部分的岩浆。尽管对这种岩浆活动如何以及在何处发生、火山样式和产物的范围以及它们对人类社会的贡献（危害、成矿、景观演变等）进行了50年的研究，关于地幔熔化的条件和时间尺度、可能熔化的不同类型的岩石以及这些不同地下岩石区域的大小和形状，仍然存在许多问题。此外，科学家们仍然对所有这些因素如何影响最终喷发的岩浆类型以及喷发的风格（例如，多大，多频繁，爆炸性如何）有一个非常不完整的了解。这个研究项目利用最近喷发的稀有火山岩玻安岩来解决这些问题。这些岩石是在高温条件下将H2O加入浅地幔中形成的。地球化学、同位素地球化学和这些岩石中天然存在的放射性元素分布的工具将被用来分析一组已经存在的、独特的样本。项目目标是确定：（1）俯冲带下地幔成分的多样性和空间尺度，（2）它们融化的时间尺度，（3）岩浆如何形成并迁移到地表，以及（4）这如何有助于火山活动。 对这些问题的回答对社会和国家利益具有更广泛的影响，因为它们提供了有关俯冲带岩浆活动和火山活动（以及相关的危害和益处）的过程的信息，俯冲带既发生在美国西海岸，也发生在我们在美洲、加勒比和太平洋沿岸的许多伙伴国家（如日本、台湾和新西兰）的沿着。此外，该项目将资助一个EPSCoR州（夏威夷）的一个机构，支持一名早期职业研究人员，并通过NOAA外展引擎和U夏威夷网站进行公共外展。该项目将研究洋际俯冲带火山活动，使用一套独特的年轻玻安岩和相关的镁铁质/超镁铁质样品，这些样品来自9个马塔火山和邻近的弧后和弧后火山（劳东北和福努阿莱扩散中心）。U系列不平衡和Sr-Nd-Pb-Hf同位素分析，以及已收集的火山玻璃、矿物和全岩中的主/微量元素丰度，将用于研究活动洋间弧/弧后的高分辨率（公里级）地幔楔不均匀性、俯冲流体输入的近千年变化以及玻安岩和其他岩浆岩石成因的条件。假设将进行测试，以解决如何从俯冲板片的流体引起上覆地幔熔融，如何不同的地幔熔融的组合物，如何不同的岩浆被输送到表面的方式，保持大的变化，在小的空间尺度上的岩浆成分，以及这些不同的过程的时间尺度，其中初步数据表明，在某些情况下，可能会比迄今为止实现的要快得多。

项目成果

Geologic and Structural Evolution of the NE Lau Basin, Tonga: Morphotectonic Analysis and Classification of Structures Using Shallow Seismicity

• DOI: 10.3389/feart.2021.665185
• 发表时间: 2021-02
• 作者: Melissa O. Anderson;Chantal Norris-Julseth;K. Rubin;K. Haase;M. Hannington;A. Baxter;M. Stewart

Extensive young silicic volcanism produces large deep submarine lava flows in the NE Lau Basin

• DOI: 10.1007/s00445-018-1211-7
• 发表时间: 2018-03
• 期刊: Bulletin of Volcanology
• 影响因子: 3.5
• 作者: R. Embley;Kenneth H. Rubin

Recent Eruptions Between 2012 and 2018 Discovered at West Mata Submarine Volcano (NE Lau Basin, SW Pacific) and Characterized by New Ship, AUV, and ROV Data

• DOI: 10.3389/fmars.2019.00495
• 发表时间: 2019-08-20
• 期刊: FRONTIERS IN MARINE SCIENCE
• 影响因子: 3.7
• 作者: Chadwick, William W., Jr.;Rubin, Kenneth H.;Embley, Robert W.
• 通讯作者: Embley, Robert W.