Collaborative Research: Rio Grande Rise: New Questions on Plume Dynamics, Atlantic Tectonic Evolution and an Important Window to the African LLSVP

格兰德河海隆位于巴西海岸外的南大西洋，是一个火山性的海洋高原，形成于或靠近大西洋中脊扩张中心。 现在位于非洲外海的沃尔维斯海岭也在接近同一时间在中大西洋海岭附近形成。格兰德河海隆的体积大约是沃尔维斯海岭的两倍，它们共同记录了约1.3亿年的板内火山活动，并被假设为代表了深部地幔柱的产物。尽管格兰德河隆起面积极大，火山活动历史悠久，但它确实是一片未知的土地。根据现有的少数岩石样本，格兰德河海隆似乎形成于7000万至9000万年前，与沃尔维斯海岭的老部分同时形成。为了了解这些大型火山地貌的历史，该项目将进行一次海上航行，前往格兰德河海隆，从40座海山、裂谷带山谷和陡峭的悬崖调查和收集岩石样本。这些新数据将使我们能够彻底调查格兰德河海隆的形成及其与已经收集到岩石样本的沃尔维斯海岭的关系。 新的数据还将提供一个独特的机会，以解决与板块构造有关的广泛问题，包括格兰德河隆起如何与非洲大型低剪切波速度区（LLSVP）的深层致密地幔区有关，该区域被认为是地幔柱产生的地方。 该项目是与巴西科学家和学生合作开展的。新收集的地质年代学、地球化学和地球物理数据将对以下两个主要科学问题做出重大贡献：（1）格兰德河海隆是由地幔柱动力学、浅层构造还是两者共同作用形成的？(2)与非洲大低剪切波速度区（LLSVP）深部致密地幔带有关的地幔源区是什么？ 确定格兰德河隆起和沃尔维斯海岭火山活动何时与板块内热点火山活动单独相关是至关重要的，因为这些火山活动痕迹对于计算追溯到1.3亿年前的非洲绝对板块运动和全球板块回路模型至关重要。此外，如果大体积的格兰德河上升-沃尔维斯海岭系统及其源链接回LLSVP的边缘，这将提供一个独特的可能性，以调查其极端富集的成分是否代表下地幔的主要成分。

The Rio Grande Rise in the South Atlantic off of the coast of Brazil is a volcanic oceanic plateau that formed on, or close to the Mid-Atlantic Ridge spreading center. The Walvis Ridge, which is now located off of Africa, also formed near the Mid-Atlantic Ridge close to the same time. The Rio Grande Rise is about twice the volume of Walvis Ridge and together they record ~130 Myr of intra-plate volcanism and are hypothesized to represent the products of a deep mantle plume. Despite its extremely large size and prolonged volcanic history, Rio Grande Rise truly is terra incognita. Based on the few rock samples available, it appears that Rio Grande Rise formed between 70 and 90 million years ago at the same time as the older part of Walvis Ridge. To understand the history of these large volcanic features, this project will carry out a seagoing cruise to the Rio Grande Rise to survey and collect rock samples from 40 seamounts, rift zone valleys and steep escarpments. These new data will allow a thorough investigation of the formation of the Rio Grande Rise and its relationship to the Walvis Ridge where rock samples have already been collected. The new data will also provide a unique opportunity to address a wide range of questions relating to plate tectonics, including how the Rio Grande Rise is related to the deep dense mantle zone of the African large low shear wave velocity province (LLSVP) which is thought to be a place where mantle plumes are generated. This project is in collaboration with Brazilian scientists and students. The project supports the training of U.S. graduate and undergraduate students.The newly collected geochronological, geochemical and geophysical data will contribute significantly to the following two major science questions: (1) Is Rio Grande Rise shaped by plume dynamics, shallow tectonics or both and what are the consequences for understanding hotspot evolution? (2) What are the mantle sources related to the deep dense mantle zone of the African large low shear wave velocity province (LLSVP)? Determining when Rio Grande Rise and Walvis Ridge volcanism became associated with intra-plate hotspot volcanism alone is fundamental as these volcanic traces are essential for calculating African absolute plate motion and global plate circuit models back to 130 million years. Moreover, if the large volume of the Rio Grande Rise-Walvis Ridge system and its source link back to the edge of the LLSVP, this will provide a unique possibility to investigate whether their extreme enriched composition represents a major component in the lower mantle.