Collaborative Research: Tectonic and Magmatic Processes during Early-Stage Rifting: an Integrated Study of Northern Lake Malawi, Africa

合作研究：早期裂谷期间的构造和岩浆过程：非洲马拉维湖北部的综合研究

• 批准号: 1109512
• 负责人: Matthew Pritchard
• 金额: $ 7.93万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-15 至 2018-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1109512&HistoricalAwards=false
• 关键词: Collaborative; Research; Tectonic; Magmatic; Processes

Although the concept that thick continental lithosphere extends and ultimately ruptures has been accepted for over 50 years, the conditions required for this to occur and the factors that are most important in controlling the style of rifting, the formation and maintenance of tectonic segmentation and the initiation of magmatism remain contentious. This is especially true of the earliest stages of extension, in part because most studies focus on successfully rifted margins and mature rifts, where extensive stretching, syn- and post-rift magmatism, and post-breakup sedimentation overwrite and bury the record of incipient extension. Understanding how, why and when features that are characteristic of mid-ocean ridges and rifts first form and evolve during early rifting is essential for a broader understanding of plate divergence. The primary scientific goal of this project is to examine the emergence and early evolution of two fundamental features of all divergent plate boundaries: magmatism and segmentation. Magmatism accommodates a significant percentage of plate separation at most mid-ocean ridges and late-stage rifts. Likewise, transform faults demarcate discrete spreading segments in mid-ocean ridges, which are broadly characterized by more robust magmatism at their centers than at their edges. Well-developed magmatic and tectonic segmentation is also observed in late-stage rifts and new ocean basins However,little is known about the controls on the initiation and development of magmatism and segmentation in young rifts. Specifically, th PIs seek to address the following questions: ? When, where and why does magmatism initiate in rifts, and what is its role in accommodating extension? ? What controls the development of tectonic segmentation in early-stage rifts? How is it manifested in 4D patterns of magmatism and deformation. The project consists of an integrated geophysical, geochemical and geological study of the northern Lake Malawi region in the East African Rift System (EARS) to address these questions. This is one of the few places in the world that has all of the ingredients necessary for a comprehensive study of early rifting. Active and passive seismic data and MT data will reveal the 3D structure of the crust and lithosphere at a variety of length scales, from the architecture of border faults and accommodation zones to the distribution of deformation and magma (if present) in the mantle lithosphere. Surface deformation, seismicity, and rift stratigraphy, as well as geochronology, thermobarometry and geochemistry of volcanic rocks, will yield constraints on the origin of magmatism and the evolution of deformation and magmatism at a range of time scales, including possibly variable contributions from sub-lithospheric versus lithospheric sources. Comparisons of active and cumulative deformation patterns will enable the evaluation of the importance of episodicity, seismicity and magmatism in accommodating extension and how they relate to segmentation. This powerful combination of temporal and spatial constraints will produce unique insights into the initiation of segmentation and magmatism during continental rifting.

尽管较厚的大陆岩石圈扩展并最终接受破裂的概念已被接受了50多年，但发生的条件以及在控制裂谷风格，构造和维护构造和启动方面最重要的因素和最重要的因素岩浆主义仍然有争议。最早的扩展阶段尤其如此，部分是因为大多数研究都集中在成功的裂痕和成熟的裂痕上，在那里，广泛的伸展，合成和裂痕后岩浆和分裂后沉积覆盖物和掩埋了初期延伸的记录。了解如何，为什么和何时在早期裂开期间的中山脊和裂痕的特征和裂纹的特征，对于更广泛的理解板发散至关重要。该项目的主要科学目标是检查所有不同板块边界的两个基本特征的出现和早期进化：岩浆和分割。在大多数海洋山脊和晚期裂谷中，岩浆症可容纳大部分的板块分离。同样，变换断层在中山脊中划定离散的传播段，其特征在其中心比在其边缘更强大的岩浆作用。在后期裂谷和新海盆中也观察到了发达的岩浆和构造分割，但是，关于岩浆岩岩的启动和发展和幼年裂谷的启动和发展的控制知之甚少。具体来说，PI试图解决以下问题：？岩浆主义何时，何时何地启动裂谷，其在适应扩展方面的作用是什么？ ？是什么控制早期裂谷中构造分割的发展？它如何以岩浆和变形的4D模式表现出来。该项目由东非裂谷系统（EARS）北部马拉维湖地区（EARS）的综合地球物理，地球化学和地质研究组成，以解决这些问题。这是世界上少数几个具有对早期裂谷进行全面研究所必需的成分的地方之一。主动和被动的地震数据和MT数据将在各种长度尺度上揭示地壳和岩石圈的3D结构，从边界断层和住宿区的结构到地幔岩石圈中的变形和岩浆的分布（如果存在）。表面变形，地震性和裂谷地层以及火山岩的热量计量学和地球化学将对岩浆作用以及在时间尺度上的变形和岩浆作用的演化产生限制，包括从子范围内的贡献，包括从子量表中产生。岩石圈与岩石圈源。主动和累积变形模式的比较将能够评估情节性，地震性和岩浆性在适应扩展中的重要性及其与分割之间的关系。时间和空间约束的强大组合将产生对大陆裂谷期间分割和岩浆作用的独特见解。