Collaborative Research: Structure and Quaternary Kinematics of Amagmatic Rifting in the Central Afar Triple Junction

合作研究：中阿法尔三重交界处岩浆裂谷的结构和第四纪运动学

• 批准号: 1419906
• 负责人: Francisco Gomez
• 金额: $ 31.82万
• 依托单位: University of Missouri-Columbia
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-15 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1419906&HistoricalAwards=false
• 关键词: Collaborative; Research; Structure; Quaternary; Kinematics

The Afar region in East Africa encompasses the only on-land exposure of a rift-rift-rift triple junction and, hence, affords an unusual opportunity to study the extensional tectonism from the early break-up of continents to seafloor spreading. Present-day extension across the Afar is accommodated by magmatic, axial rift zones (Red Sea, Gulf of Aden, and the main Ethiopian Rift) and amagmatic extension across the region in between. Although much geological and geophysical research has been conducted in the region, knowledge on how extension is accommodated here remains poorly understood. This study will evaluate competing tectonic models of rift formation in the Afar through a combination of structural and landscape analysis, remote sensing, and geochronology. The resultant understanding of extension across Afar rift will provide insight into the evolution of rift-rift-rift triple junctions and continental rifting, in general. The project will advance desired societal outcomes through participation of underrepresented minorities in STEM, improved STEM education through curricular enhancement at a HBCU institution, development of a diverse, globally competitive STEM workforce through the training of graduate and undergraduate students, and increased partnerships through international collaboration.This study will examine the structure and late Cenozoic tectonism in the Afar region in an effort to decipher the neotectonic framework of an active rift-rift-rift triple junction. The interaction between the Gulf of Aden and Red Sea rifts have led to the development of a large-scale accommodation zone that presently is marked by half grabens and tilted fault blocks in central Afar. Understanding the partitioning of extension across Afar rift will provide insight into the evolution of rift-rift-rift triple junctions and continental rifting, in general. This research project aims to conduct fieldwork and remote-sensing analyses that will provide a basis for estimating the magnitude extension across part of the central Afar accommodation zone, as well as Quaternary kinematics. The Afar Stratoid volcanic rocks (4.0 ? 1.0 Ma) are a regionally extensive lava surface that predates the initiation of grabens in the Afar and, hence, provides a viable datum for estimating the magnitude of extension during the Quaternary. Additionally, comparison of long-term (Quaternary) deformation with more recent kinematics (e.g., from late Pleistocene landforms and available GPS observations) provides an initial means of assessing the evolution of the accommodation zone (e.g., co-axial strain versus progressive strain and rotation). Combining structural and neotectonic analyses, the project will accomplish the following: 1) constrain structural geometries and the viability of a regional datum for restoration; 2) estimate horizontal extension across part of the central Afar, including estimation of the contribution of small faults to regional strain; 3) estimate late Pleistocene rates of faulting for major faults using tectonic landforms; 4) use long-term drainage evolution for spatial and temporal constraints on initiation of amagmatic extension.

东非的阿法尔地区是陆地上唯一暴露出裂谷-裂谷-裂谷三联结的地区，因此为研究从大陆早期解体到海底扩张的伸展构造作用提供了一个不同寻常的机会。今天跨越阿法尔河的延伸是由岩浆、轴向裂谷带(红海、亚丁湾和埃塞俄比亚主要裂谷)和介于两者之间的岩浆延伸穿过该地区而形成的。尽管在该地区进行了大量的地质和地球物理研究，但对这里如何适应扩建的了解仍然很少。这项研究将通过结合结构和景观分析、遥感和地质年代学来评估阿法尔裂谷形成的相互竞争的构造模型。由此产生的对跨越阿法尔裂谷的伸展的理解将提供对裂谷-裂谷-裂谷三重结合部和大陆裂谷的总体演化的洞察。该项目将通过未被充分代表的少数族裔参与STEM，通过加强HBCU机构的课程来改善STEM教育，通过培训研究生和本科生发展多样化的、具有全球竞争力的STEM劳动力，以及通过国际合作增加伙伴关系，来促进预期的社会成果。这项研究将研究阿法尔地区的结构和晚新生代构造作用，以努力破解活跃的裂谷-裂谷-裂谷三合一的新构造框架。亚丁湾和红海裂谷之间的相互作用导致了一个大规模的住宅区的发展，目前阿法尔中部的特点是半地块和倾斜的断块。了解跨越阿法尔裂谷的伸展划分，将有助于洞察裂谷-裂谷-裂谷三重结合部和大陆裂谷的总体演化。这一研究项目旨在进行实地调查和遥感分析，为估计阿法尔居住区中部部分地区的震级扩展以及第四纪运动学提供基础。阿法尔类层状火山岩(4.0~1.0 Ma)是一个区域性广泛的熔岩表面，早于阿法尔地块的形成，因此为估计第四纪的伸展程度提供了可靠的依据。此外，长期(第四纪)形变与较新运动学的比较(例如，来自晚更新世地貌和现有的GPS观测)提供了评估调节带演化的初步手段(例如，同轴应变与渐进应变和旋转)。结合构造和新构造分析，该项目将完成以下工作：1)约束用于恢复的区域基准的构造几何和可行性；2)估计阿法尔中部部分地区的水平伸展，包括估计小断层对区域应变的贡献；3)利用构造地貌估计主要断层的晚更新世断层速率；4)利用长期的排水演化对岩浆伸展的启动进行空间和时间上的限制。