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.

在数十亿个地球历史上，大洲将其定期组装成超级智慧：在蔓延到pangea之前，它加入了美洲到欧洲和非洲的单一陆地。 Rodinia（大约9亿年前）和Nuna“原始寿命”的“ proterokoic”时间间隔。 （想象一下美洲的未来，使课程逆转并漂流以关闭大西洋，并与欧洲重新统治，and and and and and and and and and and and and and and and and and and and，全球和澳大利亚，将这些想法变成了旧的超大型“内部”，这有助于塑造我们对数十亿年的地球不断发展的深层内饰的看法，以及地理环境，以形成矿藏该项目使用两种竞争性的实验室测量方法来确定大陆如何具有地球表面：岩石记录的地磁领域Nuna和Rodinia Supercondinental Landmasses中的碎片：西非，尤其是摩洛哥的反阿特拉斯山脉，为古代火山门岩石系统（“ Mafic Dikes”）的两种方法提供了一种机会，可以生产各种年龄段对NUNA和Rodinia Landmasses的更准确的重建，并发现地球项目的模式将涉及在野外收集样品，实验室对这些标本的分析，以及在我们的NORNALS中出版的结果。与该项目相关的重要社会包括培训。成员对长期地球动物的看法：超脑量是否倾向于恢复为“内而外”的事先配置。在庞格的超强或沿着外围的中间，这对上述辩论至关重要。从Stud Y获得的约会杆将填补西非的Tector运动学历史上的显着空白，并在Nuna和Rodinia e关于超大型过渡风格的辩论中。