Collaborative Research: Investigating the Relationships Between Magmatic 'Flare-Ups', Crustal Rheology, and Arc Collapse

合作研究：调查岩浆“爆发”、地壳流变学和弧塌陷之间的关系

• 批准号: 1945287
• 负责人: Stacia Gordon
• 金额: $ 26.09万
• 依托单位: Board of Regents, NSHE, obo University of Nevada, Reno
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-15 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1945287&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Relationships; Between

Subduction zones, or areas where oceanic tectonic plates are pulled into the deep Earth, are one of the most dynamic locations on our planet. Importantly, they facilitate the transfer of magma from the Earth’s interior mantle layer to its surface. This magmatism is most clearly expressed as volcanic eruptions, and several lines of evidence suggest that this process is how continental crust has been made throughout Earth’s history. Nevertheless, the rate of magma transfer is not constant. There are well-documented periods of intense magmatism within subduction zones that are known as magmatic ‘flare-ups’. These punctuated events represent a large transfer of material and thermal energy into the Earth’s crust, and delineating their causes and consequences is important for understanding the long-term evolution of these dynamic tectonic settings. This study is focused on the relationship between magmatic flare-ups and deformation of the crust by comparing two periods of intense magmatism within the North Cascade Range, Washington, that occurred 78–60 and 50–45 million years ago. This area is ideal for the study because subsequent tectonic events, combined with erosion, have juxtaposed rocks that represent a variety of crustal depths during both flare-up events and have exposed these rocks at the Earth’s surface. The researchers will use this natural laboratory to create a detailed timeline of magmatic input compared to regional evidence for thickening and subsequent thinning of the Earth’s crust, faulting, and flow of ductile, weak crust. As part of this project the researchers will produce a scientific podcast that will communicate the results of this study to the general public. The podcast will highlight the role of women geoscientists in the project, with the goal of increasing recruitment to and retention of women in STEM-related careers. The proposed research will document the rheological evolution of continental arc crust during and between magmatic flare-up events. The researchers propose to exploit a well-exposed and relatively well-studied crustal section in the North Cascades, Washington, which preserves a record of magmatism, metamorphism, and deformation in the deep to upper crust during and between two flare-up events in the latest Cretaceous and Paleogene. Underthrusting and incorporation of sediment into the deep levels of the arc occurred during part of the older flare-up, and the end stage of the younger flare-up is coeval with exhumation of the deep arc crust. The researchers will utilize cutting-edge geochemical, geochronologic, thermobarometric, and field techniques on a combination of igneous intrusions and metasedimentary rocks within the arc, including those exposed within major fault systems. A key component of this study will be to create a high temporal resolution record of magma addition during the two flare-up events using uranium-lead zircon geo-/thermochronology that can be directly compared to a similar record of metamorphism, ductile deformation, and faulting determined by a combination of uranium-lead zircon, monazite, and titanite geo-/thermochronology, application of the new quartz in garnet geobarometer, and traditional field and microstructural study. This approach will provide a holistic understanding of magmatic flare-ups and how they affect the rheology of subduction zone crust on a 1-million-year-scale. In particular, the principal investigators will address: the temporal relationship between a weakened deep crust and flare-up magmatism; when the arc-bounding fault systems became active relative to flare-ups; how deformation was partitioned across different lithologies and structures; if and when crustal melting occurred during a flare-up; and if crustal thickness stayed constant during and between flare-ups. The broader impacts will include training of graduate students and creating a long-lasting program for public outreach through the development and advertisement of a podcast series tied to the roadside geology of the proposed research area, which is in the Ross Lake National Recreation Area.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.

俯冲带，即海洋构造板块被拉入地球深处的区域，是地球上最具活力的地区之一。重要的是，它们促进岩浆从地球内部地幔层转移到其表面。这种岩浆作用最明显地表现为火山喷发，并且有几条证据表明，这个过程就是整个地球历史上大陆地壳的形成过程。然而，岩浆转移的速度并不是恒定的。俯冲带内存在着强烈的岩浆活动时期，被称为岩浆“爆发”，这是有据可查的。这些间断事件代表着物质和热能大量转移到地壳中，描述其原因和后果对于理解这些动态构造环境的长期演化非常重要。这项研究通过比较华盛顿州北喀斯喀特山脉内分别发生在 78-60 和 50-45 百万年前的两个强烈岩浆活动时期，重点研究岩浆爆发与地壳变形之间的关系。该区域非常适合进行研究，因为随后的构造事件与侵蚀相结合，在两次爆发事件中并置了代表不同地壳深度的岩石，并将这些岩石暴露在地球表面。研究人员将利用这个自然实验室创建详细的岩浆输入时间表，与地壳增厚和随后变薄、断层以及延性、弱地壳流动的区域证据进行比较。作为该项目的一部分，研究人员将制作一个科学播客，向公众传达这项研究的结果。该播客将强调女性地球科学家在该项目中的作用，目标是增加女性在 STEM 相关职业中的招聘和保留。 拟议的研究将记录岩浆爆发事件期间和之间大陆弧地壳的流变演化。研究人员建议开发华盛顿州北喀斯喀特地区一个暴露良好且研究相对充分的地壳部分，该部分保存了白垩纪末期和古近纪两次爆发事件期间和之间从深部到上地壳的岩浆作用、变质作用和变形记录。在较老的爆发期间，沉积物被冲断并并入弧的深层，而较新的爆发的末期与深部弧地壳的折返同时发生。研究人员将利用尖端的地球化学、地质年代学、热压测量和现场技术来研究弧内的火成岩和变沉积岩，包括那些暴露在主要断层系统内的岩浆岩。这项研究的一个关键部分是使用铀铅锆石地质/热年代学创建两次爆发事件期间岩浆添加的高时间分辨率记录，该记录可以直接与由铀铅锆石、独居石和钛矿地质/热年代学组合确定的变质作用、韧性变形和断层的类似记录进行比较，以及新石英在石榴石中的应用 地质气压计以及传统的现场和微观结构研究。这种方法将提供对岩浆爆发及其如何影响一百万年规模的俯冲带地壳流变学的全面了解。主要研究人员将特别讨论： 深层地壳减弱与岩浆爆发之间的时间关系；当弧边界断层系统相对于爆发变得活跃时；变形如何在不同的岩性和结构之间划分；如果在爆发期间发生地壳熔化；以及地壳厚度在爆发期间和爆发之间是否保持恒定。更广泛的影响将包括培训研究生，并通过开发和宣传与拟议研究区域（位于罗斯湖国家休闲区）的路边地质相关的播客系列来创建长期的公共宣传计划。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

WHAT HAPPENS TO LARGE DISPLACEMENTS ON PALEOGENE STRIKE-SLIP FAULTS IN CENTRAL BRITISH COLUMBIA AND ALASKA TO THE SOUTH?

不列颠哥伦比亚省中部和阿拉斯加南部的古近纪走滑断层的大位移会发生什么？

• DOI: 10.1130/abs/2022am-382628
• 发表时间: 2022
• 期刊: Geological Society of America Abstracts with Programs
• 作者: Miller, Robert;Eddy, Michael;Gordon, Stacia
• 通讯作者: Gordon, Stacia

TRACKING THE COLLAPSE AND EXHUMATION OF A CONTINENTAL MAGMATIC ARC: THE RECORD FROM ZIRCON DEPTH PROFILING ANALYSES OF NORTH CASCADES METASEDIMENTARY ROCKS

追踪大陆岩浆弧的崩塌和折返：北喀斯喀斯变质沉积岩锆石深度剖面分析的记录

• DOI: 10.1130/abs/2022am-380806
• 发表时间: 2022
• 期刊: Geological Society of America Abstracts with Programs
• 作者: Gordon, Stacia M.;Miller, Robert B.;Eddy, Michael;Kylander-Clark, Andrew R.C.;Langdon-Lassagne, Elizabeth
• 通讯作者: Langdon-Lassagne, Elizabeth

METASEDIMENTARY ROCKS OF THE NORTH CASCADES CONTINENTAL MAGMATIC ARC: IMPORTANT TRACKERS OF THE RHEOLOGIC HISTORY OF AN ARC SYSTEM

北喀斯喀特大陆岩浆弧的变沉积岩：弧系统流变历史的重要追踪者

• DOI: 10.1130/abs/2021am-365514
• 发表时间: 2021
• 期刊: Geological Society of America Abstracts with Programs
• 作者: Gordon, Stacia;Hanson, Ann;Sauer, Kirsten B.;Miller, Robert B.
• 通讯作者: Miller, Robert B.