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

合作研究：里奥格兰德海隆：羽流动力学、大西洋构造演化的新问题和非洲 LLSVP 的重要窗口

• 批准号: 1558681
• 负责人: Anthony Koppers
• 金额: $ 40万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-02-15 至 2024-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1558681&HistoricalAwards=false
• 关键词: Collaborative; Research; Rio; Grande; Rise

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.

巴西海岸附近的南大西洋里奥格兰德隆起是一个火山海洋高原，形成于大西洋中脊扩张中心或附近。 现在位于非洲附近的鲸湾海岭，也在大约同一时间在大西洋中脊附近形成。格兰德河隆起的体积约为鲸湾海岭的两倍，它们总共记录了约 130 密尔的板内火山活动，并被假设代表深部地幔柱的产物。尽管格兰德河隆起面积极其巨大，火山历史悠久，但它确实是一片未知之地。根据现有的少量岩石样本，格兰德河隆起似乎形成于 70 至 9000 万年前，与沃尔维斯海岭的较老部分同时形成。为了了解这些大型火山特征的历史，该项目将进行一次前往里奥格兰德隆起的海上航行，从40个海山、裂谷带山谷和陡峭的悬崖上调查和收集岩石样本。这些新数据将有助于彻底调查里奥格兰德隆起的形成及其与已收集岩石样本的沃尔维斯海脊的关系。 新数据还将提供一个独特的机会来解决与板块构造有关的广泛问题，包括里奥格兰德隆起与非洲大型低剪切波速省（LLSVP）的深层致密地幔带有何关系，人们认为该区域是地幔柱产生的地方。 该项目是与巴西科学家和学生合作的。该项目支持对美国研究生和本科生的培训。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）里奥格兰德海隆是由羽流动力学、浅层构造或两者共同形成的，以及是什么？这对理解热点演化有何影响？ （2）与非洲低横波速大区（LLSVP）深部致密地幔带相关的地幔来源有哪些？ 确定里奥格兰德海隆和沃尔维斯海岭火山活动何时与板块内热点火山活动相关联至关重要，因为这些火山痕迹对于计算 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Rio Grande Rise-Walvis Ridge系统的大体积及其源头连接回LLSVP的边缘，这将为研究其极端丰富的成分是否代表下地幔的主要成分提供独特的可能性。