Collaborative Research: Dry Rifting In the Albertine-Rhino graben (DRIAR), Uganda

合作研究：乌干达艾伯丁-犀牛地堑 (DRIAR) 的干裂谷

• 批准号: 2210214
• 负责人: Eliot Atekwana
• 金额: $ 72.39万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-10-01 至 2024-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2210214&HistoricalAwards=false
• 关键词: Collaborative; Research; Dry; Rifting; Albertine

The Earth’s surface is constantly moving and changing shape. In some places, like East Africa, a continent stretches to the point of breaking, forming continental rifts that, after a period of time, can form new oceans. Numerous studies show that continental rifts develop along weakened zones caused by deep intrusions of magma. Some continental rifts, however, form without evidence of magma intrusions and are known as magma-poor or "dry" rifts. In this project, an investigation of the East African Rift System will take place along the Northern Western Branch located in Uganda, East Africa where magma-poor rifting is taking place. A wide range of geophysical, geological, and geochemical observations will be collected, and numerical modeling of the region will be performed to advance our understanding of how these magma-poor rifts form and evolve. In conjunction with the scientific investigation, ]Ugandan partners will be engaged in data collection techniques. Ugandan and US graduate students will participate, underrepresented students mentored, and several open-access data sets and model products shall be developed. Societal implications of this study include advances in rifting models used for hydrocarbon exploration, improved estimates of CO2 flux into the atmosphere that occurs during continental rifting, and new insights into seismic hazards associated with active faulting. The scientific results of this project will be communicated, in part, through short educational videos geared towards public audiences. Continental rifting is an integral component of the plate tectonic paradigm, yet speculation remains about the physical processes involved in magma-poor/-dry rifting. The goal of this project is to apply a combination of geophysical, geological, geochemical and geodynamic techniques to the Northern Western Branch of the East African Rift System in Uganda to test 3 hypotheses: (1) in magma-rich rifts, strain is accommodated through lithospheric weakening from melt, (2) in magma-poor rifts, melt is present below the surface and weakens the lithosphere such that strain is accommodated during upper crustal extension, and (3) in magma-poor rifts, there is no melt at depth and strain is accommodated along pre-existing structures such as inherited compositional, structural, and rheological lithospheric heterogeneities. Observational methods in this project include: passive seismic to constrain lithospheric structure and flow patterns; gravity to constrain variations in crustal and lithospheric thickness; magnetics to constrain the thermal structure of the upper crust; magnetotellurics to constrain lithospheric thickness and the presence of melt; GNSS to constrain surface motions, extension rates, and help characterize mantle flow; geologic mapping to document the geometry and kinematics of active faults; seismic reflection analyses of intra-rift faults to document temporal strain migration; geochemistry to quantify mantle-derived fluids in hot springs and gases; and geodynamic modeling to develop new models of magma-poor rifting processes.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.

地球表面不断移动和改变形状。在一些地方，比如东非，大陆延伸到破裂的程度，形成大陆裂痕，一段时间后，可以形成新的海洋。大量研究表明，大陆裂谷沿着岩浆深层侵入造成的弱化带发展。然而，一些大陆裂谷在没有岩浆侵入证据的情况下形成，被称为贫岩浆或“干”裂谷。在该项目中，将沿着位于东非乌干达的西北分支进行东非裂谷系统的调查，那里正在发生贫岩浆裂谷。将收集广泛的地球物理、地质和地球化学观测数据，并对该地区进行数值模拟，以加深我们对这些贫岩浆裂谷如何形成和演化的理解。结合科学研究，]乌干达合作伙伴将致力于数据收集技术。乌干达和美国的研究生将参与其中，对代表性不足的学生进行指导，并开发一些开放获取的数据集和模型产品。这项研究的社会影响包括用于碳氢化合物勘探的裂谷模型的进展、改进了对大陆裂谷期间进入大气的二氧化碳通量的估计，以及对与活动断层相关的地震灾害的新见解。该项目的科学成果将部分通过面向公众的教育短片进行传播。大陆裂谷是板块构造范式的一个组成部分，但关于贫岩浆/干裂谷所涉及的物理过程的猜测仍然存在。该项目的目标是将地球物理、地质、地球化学和地球动力学技术结合应用于乌干达东非裂谷系的西北分支，以检验 3 个假设：(1) 在富含岩浆的裂谷中，通过熔融削弱岩石圈来调节应变，(2) 在贫岩浆的裂谷中，熔体存在于地表以下并削弱岩石圈，从而调节应变 在上地壳伸展过程中，以及（3）在贫岩浆裂谷中，深层没有熔化，应变沿着预先存在的结构（例如继承的成分、结构和流变岩石圈异质性）进行调节。本项目的观测方法包括：被动地震约束岩石圈结构和流动模式；重力限制地壳和岩石圈厚度的变化；磁力约束上地壳的热结构；大地电磁学限制岩石圈厚度和熔体的存在； GNSS 限制地表运动、延伸率，并帮助表征地幔流；地质测绘，记录活动断层的几何形状和运动学；裂谷内断层的地震反射分析以记录时间应变迁移；量化温泉和气体中地幔衍生流体的地球化学；该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。