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: 2021721
• 负责人: Suzan van der Lee
• 金额: $ 62.33万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-12-01 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2021721&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.

地球的表面在不断地移动和改变形状。在一些地方，比如东非，大陆延伸到断裂点，形成大陆裂缝，经过一段时间，可以形成新的海洋。大量研究表明，大陆裂谷沿着由岩浆深部侵入造成的弱化带发育。然而，一些大陆裂谷的形成没有岩浆侵入的证据，被称为岩浆贫乏或“干”裂谷。在这个项目中，东非裂谷系统的调查将沿着沿着位于东非乌干达的北方西部分支进行，那里正在发生岩浆贫乏的裂谷作用。将收集广泛的地球物理，地质和地球化学观测结果，并对该地区进行数值模拟，以促进我们对这些岩浆贫乏的裂谷如何形成和演化的理解。在进行科学调查的同时，]乌干达伙伴将采用数据收集技术。乌干达和美国的研究生将参与，代表性不足的学生将得到指导，并将开发几个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油气勘探的裂谷模型的进展，改进的估计CO2通量进入大气中发生在大陆裂谷，和新的见解与活动断层的地震危害。该项目的科学成果将部分通过面向公众的教育短片传播。大陆裂谷是板块构造范式的一个组成部分，但推测仍然是有关的物理过程中岩浆贫/干裂谷。该项目的目标是对乌干达境内的东非裂谷系北方西部分支综合应用地球物理、地质、地球化学和地球动力学技术，以检验3个假设：（1）在富含岩浆的裂谷中，应变通过岩石圈熔融弱化来调节，（2）在缺乏岩浆的裂谷中，熔体存在于地表以下，并削弱岩石圈，从而在上地壳伸展期间适应应变，以及（3）在岩浆贫乏的裂谷中，在深度处没有熔融，应变被沿着预先存在的结构（例如继承的成分、结构和流变岩石圈不均匀性）调节。这一项目的观测方法包括：被动地震，以限制岩石圈结构和流动模式;重力，以限制地壳和岩石圈厚度的变化;磁力，以限制上地壳的热结构;大地电磁，以限制岩石圈厚度和熔体的存在;全球导航卫星系统，以限制地表运动、伸展速率，并帮助确定地幔流动的特征;地质测绘以记录活动断层的几何学和运动学;裂谷内断层的地震反射分析以记录时间应变迁移;地球化学以量化热泉和气体中的幔源流体;和地球动力学模型来开发新的岩浆模型-裂谷过程不佳。该奖项反映了NSF的法定使命，并通过使用基金会知识分子的评估被认为值得支持优点和更广泛的影响审查标准。