Collaborative Research: Paleomagnetism and Geochronology of Mafic Dikes in Morocco, Reconstructing West Africa in Proterozoic Supercontinents

合作研究：摩洛哥镁铁质岩脉的古地磁学和地质年代学，重建元古代超大陆中的西非

• 批准号: 1953549
• 负责人: David Evans
• 金额: $ 39.04万
• 依托单位: Yale University
• 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: 2020-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1953549&HistoricalAwards=false
• 关键词: Collaborative; Research; Paleomagnetism; Geochronology; Mafic

Over billions of years of Earth history, continents have drifted across the globe, periodically assembling into supercontinents. Pangea was the most recent of these: a single landmass that joined the Americas to Europe and Africa, prior to spreading of the Atlantic Ocean. Pangea was likely preceded by more ancient supercontinents named Rodinia (about 900 million years ago) and Nuna (about 1.5 billion years ago), both existing within the “Proterozoic” time interval of primordial life. Although these supercontinents have names, their exact arrangements of continental fragments remain uncertain. Regardless, geologists are beginning to speculate on whether the supercontinental transitions generally have an accordion-like pattern of motion (imagine a future for the Americas reversing their course and drifting eastward to close the Atlantic Ocean and re-collide with Europe and Africa), or whether continents circumnavigate the globe (imagine the Americas continuing to drift westward to close the Pacific Ocean and collide with eastern Asia and Australia, thus turning the old supercontinent “inside-out”). These ideas help shape our view of Earth’s evolving deep interior over billions of years, and also give geographical context to the formation of mineral deposits, ancient climate records, and biological evolution at the longest timescales. This project uses two complementary methods of laboratory measurement to determine how the continents have moved across the Earth’s surface: paleomagnetism—the ancient record of the geomagnetic field that is recorded by rocks; and the isotopic dating of the age of rocks using the radioactive decay of uranium to lead. The project focuses on the least well-understood continental fragment in the Nuna and Rodinia supercontinental landmasses: the West African craton. Within West Africa, particularly the Anti-Atlas Mountains of Morocco, recent advances of geological understanding provide an opportunity to apply the two methods to ancient volcanic rock systems (“mafic dikes”) of a variety of ages, to produce more accurate reconstructions of the Nuna and Rodinia landmasses and to discover the patterns of Earth’s supercontinental transitions. The project will involve collection of rock samples in the field, laboratory analyses on those specimens, and publication of results in peer-reviewed journals. In addition to the scientific goals of the project, important societal outcomes associated with this project include training the next generation of Earth scientists in an important science, technology, engineering and mathematics (STEM) discipline; incorporation of the project’s results into public museum displays; and development of educational modules with K-12 public school teachers.Uncertainties in the configurations of supercontinents Nuna and Rodinia currently permit either of two end-member views on long-term global geodynamics: whether supercontinents tend to revert to prior configurations, or turn “inside-out.” It is also possible that they have alternated between those two patterns in time. West Africa's paleogeography is the least constrained of all major Precambrian cratons, and its previously hypothesized placement either within the middle of pre-Pangean supercontinents or along their periphery is crucial to the aforementioned debate. This project seeks to conduct an integrated paleomagnetic and geochronological study of mafic dike swarms in Precambrian inliers of the Anti-Atlas Mountains, Morocco. High-quality and precisely dated paleomagnetic poles obtained from this study will fill a notable gap in the tectonic and kinematic history of West Africa and neighboring blocks in Nuna and Rodinia, and provide essential ground-truth to the debate on supercontinental transitional styles.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.

在数十亿年的地球历史上，遍布全球，定期聚集成超强。 Pangea是最近的：一个单一的大陆群落，在蔓延到大西洋之前，它加入了美洲到欧洲和非洲。 Pangea很可能是在更古老的超级中心（大约9亿年前）和Nuna（大约15亿年前）之前的，这两者都存在于“ proterorokoic”的时代中，尽管这些超企业具有名称，但它们的确切布置仍然不确定。 Regardless, geologists are beginning to speculate on whether the supercontinental transitions generally have an accordion-like pattern of motion (imagine a future for the Americas reversing their course and driving eastward to close the Atlantic Ocean and re-collide with Europe and Africa), or whether continents circumnavigate the globe (imagine the Americas continuing to drift westward to close the Pacific Ocean and Collide with Eastern Asia and Australia, thus turning the old supercontinent “内而外”）。这些想法有助于塑造我们对数十亿年来的地球不断发展的深层内饰的看法，也为最长的时间表的矿物沉积物，古代气候记录和生物进化的形成提供了地理环境。该项目采用了两种完整的实验室测量方法来确定延续是如何在地球表面上移动的：古磁性 - 古老的地磁田地记录，岩石记录了。以及使用铀的放射性衰变铅的岩石时代的同位素年代。该项目着重于Nuna和Rodinia Supercontinental Landmasses：西非克拉顿的最不充分理解的连续片段。在西非，尤其是摩洛哥的反阿特拉斯山脉内，地质理解的最新进展为各种年龄的古代火山岩系统（“镁铁质堤防”）应用了两种方法，以产生更准确的Nuna和Rodinia Landmasses的重建，并发现地球上层超大型过渡的模式。该项目将涉及在现场收集岩石样品，对这些标本的实验室分析，并在同行评审期刊中发布结果。除了该项目的科学目标外，与该项目相关的重要社会成果还包括培训重要的科学，技术，工程和数学（STEM）学科中的下一代地球科学家；将项目的结果纳入公共博物馆展示；以及使用K-12公立学校教师的教育模块的开发。目前，超强努纳（Nuna）和罗迪尼亚（Rodinia）的配置中的司法目前允许对长期全球地球动体学的两种结束观点中的观点之一：超企业是否倾向于恢复到先前的配置，还是将“内部”转变为“内部”。它们也有可能在这两种模式之间及时具有替代方法。西非的古地理学是所有主要前寒武纪的最不受限制的，并且其先前假设的位置要么在庞吉之前的超中国中部或沿着其周围范围内对普里奥尔的辩论至关重要。该项目旨在对摩洛哥反阿特拉斯山脉前膜膜中的镁铁质堤防群进行综合的古磁和年代学研究。从这项研究中获得的高质量和精确的古磁两极将填补西非和纳纳和罗迪尼亚纽纳和罗迪尼亚邻近街区的构造和运动学历史的显着空白，并为超级社会的过渡风格提供了基本的辩论。影响审查标准。