Assessing the role of the lithospheric mantle during passive margin development - insights from the South Atlantic African margin

评估岩石圈地幔在被动边缘发育过程中的作用 - 来自南大西洋非洲边缘的见解

• 批准号: 2305552
• 负责人: Tyrone Rooney
• 金额: $ 57.23万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-01-01 至 2026-12-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2305552&HistoricalAwards=false
• 关键词: Assessing; role; lithospheric; mantle; during

Oceans and continents dominate the surface of Earth. Continental crust is thick and ancient, preserving billions of years of history. Oceanic crust is much younger. Plate tectonic processes bring together different continental plates into supercontinents. Supercontinents are then broken apart to form new oceans. This project focuses on the process of transition between continental and oceanic crust. We examine lava from the edge of a continent that has been rifted, and where an ocean has been newly created. These lavas can provide insight into how magmatism impacted the breakup process. The project focuses on the southwestern margin of the Atlantic Ocean along the coast of Angola. This region has been uplifted since the continent began to break apart. The uplift brings to the surface rocks that are usually buried under thick piles of sediment. Broader Impacts include support for undergraduate and graduate students to participate in research and training activities. The project will also create a module for use in undergraduate classes for non-science majors. The substantial hydrocarbon interests along the rifted margins of the South Atlantic have resulted in strong seismic characterization of basins along the continental margin. The seismic data provide an important interpretive framework that has recognized the presence of magmatism in the hyper-extended and supposedly ‘non-volcanic’ basins. Lavas and xenoliths, typically the most direct probe of mantle conditions at passive rifted margins, are usually buried under thick sediments. This project will obtain new petrographic, geochronologic, major and trace element, and isotopic data from volcanic rocks and xenoliths from the southern Angolan continental margin that are exposed due to uplift of the crust. This focus region provides an ideal venue to explore the transition between the richly volcanic margin that dominates further south in Namibia, and the vast sedimentary basins that define the margin further north in Angola. Analytical and interpretative aspects of the project are focused on two questions: 1) Why do basins in southern Angola exhibit the characteristics of a magma-poor volcanic margin (i.e., hyper-extended crust and thick sediment accumulation) but also experience magmatism? This question will be addressed by examining the isotopic, major and trace element characteristics of magmatism along the basin margin that is along strike with gravity highs associated with offshore magmatic features. Sub-lithosphere contributions to the lavas will be constrained using these data. 2) Is the Upper Cretaceous magmatic event in this region and synchronous African margin uplift the result of processes operating in the plate or underlying asthenosphere? This question will be addressed by examining lavas and associated mantle xenoliths that erupted along the African passive margin contemporaneous with this uplift event. The project will include an isotope study on lavas and xenoliths to explore possible source reservoirs, and a compositional study of minerals within the xenoliths. The outcome of this work could have substantial implications beyond the discipline given the importance of magmatism in influencing hydrocarbon systems along this passive rifted margin.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.

海洋并继续主导地球的表面。大陆地壳厚而古老，可保存数十亿年的历史。海洋壳还年轻。板块构造过程将不同的大陆板汇总到超强。然后，超强被拆分以形成新的海洋。该项目着重于连续和海洋地壳之间的过渡过程。我们检查了从已裂开的大陆边缘以及新创建的海洋的熔岩。这些熔岩可以提供有关岩浆作用如何影响分手过程的洞察力。该项目着重于安哥拉沿岸大西洋的西南边缘。自从继续开始分解以来，该地区就一直受到振奋。抬高将通常建在厚厚的沉积物下的地面岩石上。更广泛的影响包括支持本科生和研究生参加研究和培训活动。该项目还将创建一个用于非科学专业的本科课程的模块。沿南大西洋撕裂边缘的巨大碳氢化合物兴趣导致沿着连续tal边缘的低音表征强烈。地震数据提供了一个重要的解释框架，该框架已经认识到在超延伸和预期的“非沃尔卡尼克”基础上存在岩浆作用。熔岩和异种石，通常是被动裂痕边缘的地幔条件最直接的探针，通常将其埋在厚的沉积物中。该项目将获得新的岩石学，年代学，主要和痕量元素，以及来自南安哥拉大陆边缘的火山岩和异种石的同位素数据，这些数据由于地壳的抬高而暴露了。该焦点区域提供了一个理想的场所，可以探索纳米比亚更南部的富含火山边缘的过渡，以及在安哥拉北部北部定义边缘的疫苗沉积贝斯。该项目的分析和解释性方面集中在两个问题上：1）为什么安哥拉南部的低音表现出岩浆贫困的火山缘的特征（即超延伸的外壳和厚实的沉积物堆积），又有岩浆岩岩呢？该问题将通过检查沿盆地边缘的岩浆性的同位素，主要和痕量元素特征来解决这个问题，该特征沿着与海上岩浆特征相关的重力高。使用这些数据将限制对熔岩的亚地圈贡献。 2）该区域中的白垩纪岩浆事件和同步非洲边缘升高是在板或下层下层中运行的过程的结果吗？这个问题将通过检查熔岩和相关的地幔Xenoliths来解决，这些熔岩和相关的外壳异义石在非洲被动边缘爆发了这一提升事件。该项目将包括一项关于熔岩和异种石的同位素研究，以探索可能的来源储量，以及对异种岩内矿物质的组成研究。鉴于岩浆主义影响沿这种被动裂痕的边缘影响碳氢化合物系统的重要性，这项工作的结果可能具有重大影响。这项奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的审查标准来评估的值得支持的。