Collaborative Research: Constraining the temporal evolution of mantle plume contributions to magmatism in the Turkana Depression

合作研究：限制图尔卡纳凹陷地幔柱对岩浆作用的时间演化

• 批准号: 1551872
• 负责人: Tyrone Rooney
• 金额: $ 21.01万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1551872&HistoricalAwards=false
• 关键词: Collaborative; Research; Constraining; temporal; evolution

The process by which the Earth's continental masses split apart to form new oceans is a central tenet of the plate tectonic paradigm. This project focuses on one of the most important features of continental rifted margins - that is the origin of magmas that are erupted within them. While the construction of oceanic crust late in the rifting cycle requires voluminous magmatic activity, there is a growing understanding that magmas also play a pivotal role earlier in the rifting process. Infiltration of magma into the tectonic plate during rift initiation contributes to the rifting process by weakening and focusing strain. However, the process of melt generation during rifting is poorly constrained. East Africa, the geographic focus area of this research project, is the classic example of a continental rift, and insights gained here have global application. Using geochemical techniques on erupted lavas, this project seeks to determine how magma is produced during continental rifting to improve our understanding of the range of contributions from various mechanisms to generate melt. The results will have important implications for understanding magma generation during the initiation and evolution of rifting, and for our understanding of the contribution of lithospheric, upper mantle, and deep mantle sources. Constraining the mechanisms which control the structure and characteristics of rifted margins has broad societal and economic benefits given much of the world's population and hydrocarbon resources and located along rifted continental margins.This proposal outlines a plan to obtain new geochemical and geochronological data in order to better understand the sources of rift lavas. The temporal variation in the role of a mantle plume and easily melted portions of the lithosphere in melt generation processes will be evaluated. The study region, in the eastern branch of the East African Rift, is a focus site of the GeoPRISMS program. The hypothesis to be tested is that volcanism in the study region has been plume influenced since the Eocene. This hypothesis will be addressed by examining the following questions: (1) What are the geochemical characteristics of the different sources of rift lavas; and (2) how have contributions from these source(s) changed over time? These questions will be addressed through a geochronological, geochemical, and paleomagnetic study of lavas with a goal to construct a detailed geochemical characterization of the sources of within-rift lavas and determine their spatial distribution and temporal variation. The study of continental rift lavas throughout the long-lived extensional process along the East African Rift has the potential to improve understanding of the range of contributions from various melt generation mechanisms. While many studies focus on isolated periods of melt production, the work proposed here would examine the temporal development of melt reservoirs and how contributions from these reservoirs evolve over time as rifting matures. Establishing how "fundamental rifting processes, and feedbacks between them, evolve in time and space" is one of the four key Rift Initiation and Evolution questions identified in the GeoPRISMS draft science plan, thus the result of this project will interface with other GeoPRISMS efforts across disciplines to examine rift development. This project has been supported in part by the Office of International Science and Engineering at NSF.

地球大陆群体分开形成新海洋的过程是板块构造范式的中心宗旨。该项目着重于大陆裂痕边缘的最重要特征之一 - 这是其中爆发的岩浆的起源。虽然在裂谷周期后期的海洋壳的构建需要大量的岩浆活动，但越来越多的理解岩浆在灌溉过程中也较早地发挥了关键作用。在裂谷开始期间，岩浆渗入构造板中，通过减弱和聚焦菌株有助于裂谷过程。但是，裂动过程中熔体产生的过程受到很大的限制。东非是该研究项目的地理重点领域，是大陆裂谷的经典例子，在这里获得的见解具有全球应用。该项目在爆发的熔岩上使用地球化学技术，旨在确定在大陆裂谷期间如何生产岩浆，以提高我们对各种机制的贡献范围的理解，以产生熔体。结果将对理解裂谷的启动和演变以及我们理解岩石圈，上地幔和深层地幔来源的贡献具有重要意义。鉴于世界上许多人口和碳氢化合物资源，限制控制裂痕边缘的结构和特征的机制具有广泛的社会和经济利益。该提案概述了一项计划，概述了一项计划，以获取新的地球化学和地球学数据，以便更好地了解Rift lavas的来源。将评估地幔羽和易于熔化的部分在熔体生成过程中的时间变化。在东非裂谷东部分支的研究区域是地质计划的重点地点。要测试的假设是，自始新世以来，研究区域的火山主义一直受到羽流的影响。该假设将通过检查以下问题来解决：（1）不同裂谷熔岩来源的地球化学特征是什么； （2）这些来源的贡献随着时间的变化如何变化？这些问题将通过熔岩的年代学，地球化学和古磁研究来解决，其目标是构建裂谷内熔岩来源的详细地球化学特征，并确定其空间分布和时间变化。整个沿东非裂谷的长期延伸过程对大陆裂谷熔岩的研究有可能提高对各种熔体产生机制的贡献范围的理解。尽管许多研究集中于孤立的熔体生产时期，但此处提出的工作将研究熔体储层的时间发展以及这些储层的贡献如何随着时间的流逝而演变，随着裂谷的成熟。建立“基本的裂缝过程以及它们之间的反馈，在时空的发展”是《地理特里主义》一草案中确定的四个关键的裂谷启动和进化问题之一，因此该项目的结果将与其他地理主义跨学科的努力互动，以检查裂谷的发展。该项目已得到NSF国际科学与工程办公室的部分支持。

项目成果

Transition to magma-driven rifting in the South Turkana Basin, Kenya: Part 2

肯尼亚南图尔卡纳盆地向岩浆驱动裂谷的转变：第 2 部分

• DOI: 10.1144/jgs2021-160
• 发表时间: 2022
• 期刊: Journal of the Geological Society
• 影响因子: 2.7
• 作者: Rooney, Tyrone O.;Wallace, Paul J.;Muirhead, James D.;Chiasera, Brandon;Steiner, R. Alex;Girard, Guillaume;Karson, Jeffery A.
• 通讯作者: Karson, Jeffery A.