Collaborative Research: Testing the timing and direction of mantle exhumation at the Iberia-Newfoundland margins with low-temperature thermochronology

合作研究：用低温热年代学测试伊比利亚-纽芬兰边缘地幔折返的时间和方向

• 批准号: 2049848
• 负责人: Michael Eddy
• 金额: $ 4.61万
• 依托单位: Purdue University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-15 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2049848&HistoricalAwards=false
• 关键词: Collaborative; Research; Testing; timing; direction

The change from continents to seafloor is an important tectonic process that leads to the formation of oceanic basins. Continental breakup results in extreme thinning of continental crust and exposure of mantle lithosphere to the seafloor before the start of seafloor spreading. The best-studied margin is the Iberia-Newfoundland margin in the North Atlantic. Previous work on the Iberia-Newfoundland margin provides the foundation for our understanding of the structure of these basins. However, multiple models have been proposed, each with slight differences. The timing, direction, and number of faults have direct implications on the evolution of these margins, as well as subsequent seawater alteration, which affects the habitability of the seafloor. This study will address questions on timing and structure of faulting that leads to separation of continents. This study will use the minerals apatite and zircon to evaluate the timing and direction of faulting, as well as when the margin cooled enough to allow key chemical reactions to occur. These key reactions are believed to be critical to understanding the evolution of life on Earth. The project will engage with a USC Communications PhD student to produce a podcast mini-series that explores the scientific research in this proposal and scientific communication practices for diverse audiences. In addition, a graduate student in the PIs lab will initiate the first Diversity, Equity, and Inclusion (DEI) poster session for graduate and undergraduate students from the Department of Earth Sciences and Department of Marine and Environmental Biology at USC.The complex interactions between faulting, magmatism, and serpentinization at hyper-extended margins have fueled geophysical, geochemical, and numerical modeling investigations for decades. However, there is still debate over first order questions about timing and mechanics of the transition from continental breakup to mantle exhumation and seafloor spreading. These include the temporal relationship of faults that accommodate mantle exhumation, the number and directionality of faults in the exhumed mantle section, and the thermal history of the lithosphere during mantle exhumation and seafloor alteration. This project is the first comprehensive low temperature thermochronology study to constrain the cooling history of the rocks exposed within and adjacent to the exhumed mantle section of the Iberia-Newfoundland margins, the only hyper-extended margin that has been systemically sampled. The project will use zircon and apatite recovered from igneous intrusions, syn-rift sediments, and exhumed continental crust from nine drill cores that make up a horizontal transect across the exhumed mantle section. These data will be used to track lithospheric cooling below ~200C (zircon (U-Th)/He) and ~80C (apatite (U-Th)/He), within the thermal window of serpentinization and ophicalcite formation, respectively. The results will be used to test proposed exhumation models and address three overarching research questions: 1) What is the temporal relationship between the faulting that accommodates mantle exhumation and seafloor spreading? 2) Was the mantle exhumed along one major detachment or multiple faults? 3) How does the timing of mantle exhumation faulting relate to other tectonic and petrologic processes, including the onset of seafloor spreading, serpentinization, and magmatism? These data will be used to evaluate whether faulting, serpentinization, and/or magmatism occurred over progressive exhumation from east to west or occurred in several locations simultaneously, with key implications for the transition from continental breakup to seafloor spreading and the relationship between magmatism, lithospheric extension, and mid-ocean ridge development. The rates and extents of serpentinization and ophicalcite formation will also have implications for understanding the development of conditions suitable for life on Earth. The project will engage with a USC Communications PhD student to produce a podcast mini-series that explores the scientific research in this proposal and scientific communication practices for diverse audiences. In addition, a graduate student in the PIs lab will initiate the first Diversity, Equity, and Inclusion (DEI) poster session for graduate and undergraduate students from the Department of Earth Sciences and Department of Marine and Environmental Biology at USC.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.

从大陆到海底的变化是导致海洋盆地形成的重要构造过程。大陆的破裂导致大陆地壳的极度稀疏和地幔岩石圈暴露在海底扩散之前。最佳研究的边缘是北大西洋的伊比利亚 - 纽芬兰边缘。伊比利亚 - 纽芬兰边缘的先前工作为我们理解这些盆地的结构奠定了基础。但是，已经提出了多种模型，每个模型都有微小的差异。断层的时机，方向和数量对这些边缘的演变以及随后的海水改变有直接影响，这影响了海底的可居住性。这项研究将解决有关导致大陆分离的断层时间和结构的问题。这项研究将使用矿物质磷灰石和锆石评估断层的时机和方向，以及边缘冷却时的时机，以允许关键的化学反应发生。这些关键反应被认为对于理解地球生命的演变至关重要。该项目将与USC Communications PhD学生互动，以制作播客迷你系列，该系列探索该提案和科学交流实践的科学研究。此外，PIS实验室的一名研究生将启动来自地球科学系的研究生和本科生，以及USC的海洋和环境生物学系的研究生和本科生的第一个多样性，公平和包容性（DEI）海报会议。数十年来，超扩张边缘的断层，岩浆和蛇纹石化助长了地球物理，地球化学和数值建模研究。但是，关于第一阶问题和机制从大陆分裂到地幔挖掘和海底蔓延的过渡的机制仍然存在争议。其中包括适应地幔挖掘的断层的时间关系，挖掘套截面中断层的数量和方向性以及在地幔挖掘和海底改变期间岩石圈的热历史。该项目是第一个综合的低温热量研究研究，旨在限制在Iberia-Newfoundland边缘的挖掘地幔段中暴露的岩石的冷却历史，这是唯一已系统地采样的唯一超扩张边缘。该项目将使用从火成岩的入侵，同步裂谷沉积物中回收的锆石和磷灰石，以及从九个钻芯中挖出的大陆地壳，这些钻头构成了横跨挖掘的地幔部分的水平样品。这些数据将用于在左下方（锆石（u-th）/He）和〜80c（apatite（u-th）/He）下，在蛇形化和蛇状岩形成的热窗口内跟踪岩石圈冷却。结果将用于测试拟议的挖掘模型并解决三个总体研究问题：1）容纳地幔挖掘和海底扩散的断层之间的时间关系是什么？ 2）地幔是沿着一个主要的支队还是多个断层挖掘出来？ 3）地幔挖掘断层的时机与其他构造和岩石学过程有何关系，包括海底扩散，蛇纹和岩浆作用？这些数据将用于评估断层，蛇形化和/或岩浆作用是出于从东到西的逐渐挖掘而发生的，还是同时发生在几个地方，这对从大陆分裂到海底的过渡到岩浆，岩石质，岩石层，岩石圈，岩石圈，岩石圈的关系产生了关键意义。延伸和海洋山脊发展。蛇形化和透明质酸形成的速度和范围也将对理解适合地球生命的状况的发展产生影响。该项目将与USC Communications PhD学生互动，以制作播客迷你系列，该系列探索该提案和科学交流实践的科学研究。此外，PIS实验室的一名研究生将启动来自地球科学系的研究生和本科生的首次多样性，公平和包容性（DEI）海报会议，以及USC的海洋和环境生物学系。法定任务，并被认为是值得通过基金会的智力优点和更广泛影响的审查标准来评估的值得支持的。