Collaborative Research: A Seismic Study of Oceanic-Arc Crustal Construction Processes at the Archetypal Andreanof Segment of the Aleutian Arc

合作研究：阿留申弧原型安德里亚诺夫段大洋弧地壳构造过程的地震研究

• 批准号: 1753676
• 负责人: Donna Shillington
• 金额: $ 51.08万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2020-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1753676&HistoricalAwards=false
• 关键词: Collaborative; Research; Seismic; Study; Oceanic

This project aims to understand how crust is formed in volcanic arcs above subduction zones. Crustal formation within volcanic arcs is a profoundly important process that continually replenishes the mass of the continents, whose constant weathering and erosion provide the source of elemental nutrients that drive Earth's biogeochemical cycles. Remarkably, the creation of new continental material and the recycling of material back into the mantle have remained balanced on Earth over hundreds of millions of years. Understanding this balance is key to understanding the habitability of the planet. All of Earth's crust is created from partial melts of the deeper mantle that rise upward and then freeze to form the crust. The building blocks of continental crust form when water released from a subducting tectonic plate lowers the melting temperature of the mantle, creating magma that rises and accumulates in volcanic arcs. The process of arc-crust formation has been the focus of many studies, but our understanding of these process is far from a complete. Questions persist because arc processes are complex and episodic, they occur over a range of spatial scales and depend on variables such as the age of the subducting plate and the evolutionary stage of a given arc, which may never reach a steady state. The study location of this project is the Andreanof segment of the Aleutian arc. Coincidentally, this location coincides with the epicenter of the 1957 Great Aleutian earthquake, the third largest earthquake of the last century and with the largest aftershock zone of any earthquake ever recorded. Active-source seismic techniques will be used to image the seismic velocity structure of the entire crust along and across this arc segment to address many of the unanswered questions of arc-crust formation. These same methodologies can be used to address questions related to earthquake and volcanic hazards common to volcanic arcs. The education component of this project will train a cohort of the next generation of scientists in the acquisition and advance analyses of these types of data.Through this grant an active-source seismic experiment will be conducted in the Andreanof segment of the Aleutian arc in order to study arc-crust formation processes. Many basic questions about arc-crust formation processes remain, including the source and variability of primary arc magmas, where and how these magmas fractionate to produce the characteristic arc geochemical signatures of crustal rocks, the role of water in all of these processes, the bulk composition of arc crust and its basic architecture and similarity to continental crust, the forcing functions for all of these processes and the temporal and spatial variability of those forcings, and the mass balance of the entire system. Substantial advance can be made by focused, multi-disciplinary study of an arc segment that has simple, well known magmatic and tectonic histories, well studied geochemistry, and sufficient along-strike variability to capture many of the processes that are believed to control arc-crust geochemical and structural evolution. The Andreanof segment is one of very few locations that satisfy these criteria. It consists of an intact, arc massif formed during three identifiable and dated magmatic episodes; it is only modestly deformed and exhibits along-strike variability in active volcanism from primarily basaltic in the east to andesitic/dacitic in the west. The seismic experiment supported by this grant will consist of one transect along the entire length of the segment and two arc-crossing transects. Multi-channel seismic (MCS) data, recorded on an 8-km-long streamer, and ocean-bottom seismic data, with instrument spacings of 10 to 15 km, will be acquired along each transect, and these data will be analyzed with advanced tomographic and MCS imaging methodologies to produce seismic velocity and reflectivity images that will reveal, for the first time, the full crustal architecture of an intact arc massif at a segment scale. These images will provide estimates of composition that will inform models of melt emplacement and fractionation, and enable a number of specific questions to be addressed, including: What is the bulk composition, thickness and basic architecture of oceanic-arc crust, How are variations in factors such as primary magma composition and crustal processing of magmas expressed in bulk arc crustal composition and structure, and What is the fate of mafic/ultra-mafic cumulates?This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该项目旨在了解在俯冲带上的火山弧中形成地壳。 火山弧内的地壳形成是一个非常重要的过程，它不断补充大陆的质量，其持续的风化和侵蚀提供了驱动地球生物地球化学周期的元素营养素的来源。 值得注意的是，新的大陆材料的创造以及将材料回收回地幔的回收已经在数亿年的地球上保持平衡。了解这种平衡是了解地球的可居住性的关键。地球所有的地壳都是由较深的地幔的部分融化而产生的，这些地幔向上升起，然后冻结以形成外壳。 当从俯冲的构造板中释放出水时，大陆壳的构建块会降低地幔的熔化温度，从而产生岩浆，从而在火山弧中升起并积聚。 弧形形成的过程一直是许多研究的重点，但是我们对这些过程的理解远非完整。 问题持续存在，因为ARC过程是复杂且发作的，因此它们发生在一系列空间尺度上，并取决于变量，例如俯冲板的年龄和给定弧的进化阶段，这可能永远不会达到稳态。 该项目的研究位置是阿留申弧的andreanof段。 巧合的是，这个地点恰逢1957年大阿留申地震的中心，这是上个世纪的第三大地震，也是有史以来记录的任何地震的最大余震区。 主动源地震技术将用于成像整个地壳的地震速度结构沿着该电弧段，以解决弧形形成的许多未解决的问题。 这些相同的方法可用于解决与地震和火山弧共有的火山危害有关的问题。 该项目的教育组成部分将培训下一代科学家的队列，并在对这些类型的数据进行审计和预先分析中进行培训。通过这笔赠款，将在阿留申弧的Andreanof段中进行主动源地震实验，以便研究弧形形成过程。 关于弧形形成过程的许多基本问题，包括主要弧岩浆的来源和可变性，这些岩浆的何处以及如何产生甲壳岩石的特征性弧形地球化学特征，水在所有这些过程中的作用，这些过程中的作用，这些过程中的弧形组成部分，以及与这些弧形的构成以及这些过程以及这些过程以及这些过程以及这些持续性的范围以及所有这些的序列以及所有这些构成的范围，所有这些范围的序列以及所有这些的范围，所有这些均具有强大的效果，所有这些均具有强大的效果强迫和整个系统的质量平衡。 可以通过对具有简单，众所周知的岩浆和构造历史的ARC段的重点，多学科的研究，进行良好研究的地球化学以及足够沿曲折的变异性来实现大量进步，以捕获许多可以控制ARC-CRUST CRUST地球化学和结构进化的过程。 Andreanof段是满足这些标准的极少数位置之一。它由在三个可识别和日期的岩浆发作中形成完整的弧块。它仅是适度的变形，并在活跃的火山中表现出从东方主要玄武岩到西方的安第斯山脉/丁香的影响。 该赠款支持的地震实验将由一个沿段的整个长度和两个弧形交叉的横断面组成。 多通道的地震（MCS）数据，记录在8公里长的彩流器和海底地震数据中，仪器间距为10至15 km，将沿每个样带获得10到15 km的仪器间距，这些数据将与先进的层析成像和MCS成像进行分析，以生成cr仪的构造，以揭示一项cr构成的图像，以示出一个完整的图像，该图像是第一个完整的图像，该图像是完整的，该图像是完整的，该图像是完整的，该图像是完整的，该图像是完整的，该图像构成了完整的图像。细分量表。 这些图像将提供构成的估计，这些构成将为熔体的拆卸和分馏模型提供信息，并启用许多特定问题，包括：什么是：什么是大量的组成，厚度和基本结构，是海洋 - arc arc壳的基本结构，如何在诸如主要的岩浆和构图中表现出的岩浆和结构的构图和构图的构图/超级构图和构图的变化，以及什么是构成和构造的东西，以及什么是构成和构造的东西，以及什么是构成型和构图，以及什么是构成和超级构图，以及何种型号，以及什么是构成和超级构图，以及何种型号，以及何种型号，以及何种型号，以及何种构成和岩层。累积？该奖项反映了NSF的法定任务，并通过使用基金会的知识分子优点和更广泛的影响审查标准来评估值得支持。