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

基本信息

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

项目摘要

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，或海洋构造板块被拉入地球深处的区域，是地球上最活跃的位置之一，重要的是，它们促进岩浆从地球内部地幔层转移到其表面。表现为火山喷发，并且一些证据表明，这一过程是整个地球历史上大陆地壳形成的过程。然而，岩浆转移的速度并不是恒定的，有充分记录的强烈时期。俯冲带内的岩浆活动被称为岩浆“爆发”，这些间断的事件代表着物质和热能向地壳的大量转移，描述其原因和后果对于理解这些动态的长期演化非常重要。这项研究的重点是通过比较华盛顿州北喀斯喀特山脉内发生于 78-60 年和 60 年的两个强烈岩浆活动时期，研究岩浆爆发与地壳变形之间的关系。 50-4500万年前，该地区是研究的理想地点，因为随后的构造事件与侵蚀相结合，在两次爆发事件中将代表不同地壳深度的岩石并置在一起，并将这些岩石暴露在地球表面。作为该项目的一部分，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、断层和延性弱地壳流动的区域证据进行比较。一个科学播客，将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，其目标是增加女性在 STEM 相关职业中的招聘和保留。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暴露良好且研究相对充分的地壳部分，该部分保留了岩浆作用、变质作用、在白垩纪末期和古近纪的两次爆发事件期间和之间，深部到上地壳的变形在较早的爆发期间和末期发生了冲断作用和沉积物并入弧的深层。较新的爆发与深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、热气压测量和现场技术来研究火成岩侵入和岩浆侵入。这项研究的一个关键部分是利用铀铅锆石地质/热年代学来创建两次爆发事件期间岩浆添加的高时间分辨率记录。可以直接与由铀铅锆石、独居石和钛矿组合确定的变质作用、延性变形和断层的类似记录进行比较地质/热年代学、新型石英在石榴石地质气压计中的应用以及传统的野外和微观结构研究，这种方法将提供对岩浆爆发及其如何影响一百万年俯冲带地壳流变学的全面了解。特别是，主要研究人员将解决：当弧边界断层系统相对于爆发活动时，弱化的深地壳与爆发岩浆作用之间的时间关系；以及如何划分变形。不同的岩性和结构；地壳融化是否在爆发期间发生；以及如果地壳厚度在爆发期间和之间保持恒定，更广泛的影响将包括培训研究生和制定长期的公共宣传计划。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。该奖项是 NSF 的法定使命，并通过使用基金会的智力优势和评估进行评估，被认为值得支持。更广泛的影响审查标准。