Collaborative Research: Impact of Magmatic Underplating on the Evolution of Lower Continental Crust

合作研究：岩浆底侵对下陆壳演化的影响

• 批准号: 2317815
• 负责人: Michael Williams
• 金额: $ 20.47万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-01 至 2026-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2317815&HistoricalAwards=false
• 关键词: Collaborative; Research; Impact; Magmatic; Underplating

Spectacular volcanic eruptions are visible evidence for the fundamental role of magmatism in shaping Earth’s continents. But how does magmatism create and alter the continents at great invisible depths? Earth scientists have long inferred that mafic magmas rise from the mantle and pond near the bottom of the crust in a process called “underplating”. This process produces “hot zones” in the deep continental crust which lead to melting, magma generation, and magma mixing. Few localities exist on Earth where hot zones have been uplifted and exposed at the surface for direct observation. This project explores the development and evolution of magma in an ancient hot zone of underplating, now exposed at the surface in northern Saskatchewan. This team hypothesizes that the region once existed above a major zone of underplating near the base of the continental crust. Students and scientists will collect data to understand the timing and duration of magmatism, metamorphism, and densification of the deep crust. They will develop models to better understand complex images of the lower continental crust detected by geophysicists throughout North America. The project will provide insight into the processes that lead to the formation of magmas of varying composition, the mechanisms that weaken or strengthen the deep crust, and ultimately, the processes that facilitate formation and stabilization of continental crust on Earth.Magmatic underplating is a first order petrologic and tectonic process that is central to many models for the development and evolution of continental crust. However, remote studies of the deep crust via geophysics or xenoliths commonly lack the resolution to unequivocally constrain the impacts of underplating. This project explores the hypothesis that ”intraplating”, i.e., the emplacement of mantle-derived magma into the lower continental crust above the underplate, is critical for magmatic processes (assimilation, mingling, hybridization), deformation (weakening and crustal flow), and subsequent densification +/- foundering or delamination of lower continental crust. Key insights will be gleaned from direct field observations of the most deeply exhumed section of the 20,000 km2 Athabasca granulite terrane (1.1-1.6 GPa). These exposures are inferred to have experienced 650 m.y. of lower crustal residence prior to exhumation. They represent a rare opportunity to explore crust-mantle interaction and long-term evolution of lower continental crust due to intraplating, metamorphism, melting, and densification in three distinct tectonic settings. Deliverables include: (i) constraining the timing and duration of magmatic intraplating and metamorphism in each setting, (ii) identifying and quantifying densification mechanisms, (iii) constraining the influence of metasedimentary gneisses on the composition, density, and seismic velocity structure of intraplated lower continental crust, and (iv) using field-based observations and data to develop more robust geophysical models of underplated lower continental crust. Critical geophysical goals include: (1) evaluating the degree to which the settings of underplating and intraplating can be distinguished in seismic surveys, and (2) evaluating the degree to which the integrated geophysical properties in each tectonic domain can inform more robust interpretations of the pattern of seismically fast lower crust detected beneath parts of North America. Broader impacts include: (i) Two Ph.D. and 2-4 B.S. students will carry out research projects; (ii) A virtual international workshop for Earth scientists and graduate students focused on the origin and evolution of lower continental crust will be hosted; (iii) PIs and students will convene a Lower Crustal Field Forum where participants will visit and explore the Athabasca granulite terrane and discuss general implications for lower continental crust; (iv) PIs and students will engage in Earth science outreach as part of field work in the vicinity of Stony Rapids, Saskatchewan. The goal is to involve interested teachers and students in our virtual workshop and field forum, giving them opportunities to share their own insights on the culture, people, and landscape along the edge of the Athabasca granulite terrane.This project is jointly funded by three EAR programs (Petrology & Geochemistry, Geophysics, and Tectonics) as well as the Established Program to Stimulate Competitive Research (EPSCoR).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.

壮观的火山喷发是岩浆中岩浆中基本作用在塑造地球大洲的基本作用的可见证据。但是，岩浆主义如何在很大的深度创造和改变大陆呢？地球科学家长期以来一直在推断出镁铁质岩浆从地壳底部附近的地幔和池塘上升，这一过程称为“低估”。这个过程在深色大陆地壳中产生“热区”，从而导致融化，岩浆产生和岩浆混合。地球上很少有地方在地面上升高并暴露于地表以进行直接观察。该项目探讨了岩浆在底层底层的古老热区中的发展和演变，该地区现已暴露在萨斯喀彻温省北部的地面。该团队假设该地区曾经存在于在持续地壳底部附近低估的主要区域之上。学生和科学家将收集数据，以了解岩浆性，变质和深层地壳的持续时间和持续时间。他们将开发模型，以更好地理解整个北美地区地球物理学家检测到的下连续地壳的复杂图像。该项目将洞悉导致各种组成的岩浆形成的过程，薄弱或增强深层地壳的机制，最终，促进地球上连续壳的形成和稳定的过程。杂乱无章的底层底层是一阶的岩石学和构造过程，是许多模型的中心，许多模型是许多模型的发展，并且是连续的cress crust crust crust crust cress crovest of cons convoluct of cons convoluct of的crovers of cromence of cromence of的crust。然而，通过地球物理学或异种石对深层壳的远程研究通常缺乏明确限制低估的影响的解决方案。该项目探讨了这样一个假设，即“插入式”，即将地幔衍生的岩浆嵌入下板上上方的下层连续地壳中，对于岩浆过程（同化，融合，杂交），变形（弱化和外壳流动），以及随后的+/ deensifienation +/- contrest +contuction conting或 - 连续condersivers contractions至关重要。主要的见解将从对20,000 km2 Athabasca颗粒状地形（1.1-1.6 GPA）中最深入的部分的直接现场观察中获得。这些暴露被推断为经历了650 M.Y.在挖掘之前的下地壳居住地。它们代表了一个难得的机会，可以在三种不同的构造环境中探索下层大陆壳的壳相互作用和长期大陆地壳的长期演变。可交付成果包括：（i）在每种环境中限制岩浆插发和变质的时间和持续时间，（ii）识别和量化致密机制，（iii）限制发电机片段对组成，密度，密度和地震速度对静脉内的较低型基于contrust的contrastional offient and obselental contental contectial offiplational conteptial obseptial offiptial off conseptial的影响（IIV和IIV）的影响的影响，下底层的连续地壳被淡化。关键的地球物理目标包括：（1）评估在地震调查中可以区分被淡化和插入性的设置的程度，（2）评估每个构造域中综合地球物理特性在每个构造域中可以更适合对地震属于北部地区的地震属于地震的模式更加可靠的解释的程度。更广泛的影响包括：（i）两位博士学位。和2-4 B.S.学生将进行研究项目； （ii）将举办针对地球科学家和研究生的虚拟国际研讨会，专注于下大陆地壳的起源和演变； （iii）PIS和学生将召集一个下层地壳田间论坛，参与者将参观并探索Athabasca颗粒地层，并讨论对下大陆地壳的一般影响； （iv）PIS和学生将参与地球科学宣传，作为萨斯喀彻温省Stony Rapids附近的现场工作的一部分。目的是让感兴趣的老师和学生参与我们的虚拟研讨会和现场论坛，使他们有机会分享自己对阿萨巴斯卡粒状地形边缘的文化，人和景观的见解，该项目由三个EAR计划（Petrology＆Geochoctrogy＆Geocyporcy，Geophysics，Geophysics和tectorsics）以及竞争竞争的研究（perrology＆Geoctortic和Geocyportion）共同资助。 NSF的法定使命，并使用基金会的知识分子优点和更广泛的审查标准来评估，被认为是宝贵的支持。