Along-strike variations in synrift magmatism on the Eastern North American Margin

北美东部边缘同裂谷岩浆作用的沿走向变化

• 批准号: 1654629
• 负责人: Donna Shillington
• 金额: $ 13.17万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-04-15 至 2021-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1654629&HistoricalAwards=false
• 关键词: Along; strike; variations; synrift; magmatism

Continental breakup to form new oceans is often accompanied by extensive outpouring of magmatism. Magmas may make continental breakup possibly by heating up and weakening continental tectonic plates. Volcanism associated with these events has also been associated with major extinction events on Earth. Despite the importance of magmatism during continental breakup, very little is known about the total volume of magmatism involved during rifting and how the volume varies between rift systems. The continental margin off the coast of the eastern U.S. is one of the best examples in the world of a continental breakup event associated with extensive magmatism. One of the biggest magmatic events in history occurred during the breakup of the supercontinent of Pangea and opening of the Atlantic Ocean. This project will involve the analysis of existing marine seismic data collected across the margin offshore North Carolina in 2014 to quantify the volume and distribution of magma frozen in the crust and how it relates to the structures that allowed breakup to occur. The project supports the training of an undergraduate student.Magmatic intrusions contribute to the growth and modification of the crust of the Earth and strongly influence strain localization in a variety of tectonic settings. Despite this, very few constraints exist on the 3-D distribution of magmatic intrusions throughout the crust in a tectonic setting that can be used to understand the controls on their distribution and the consequences for crustal modification and deformation. This project focuses on magmatism in rifts, but the scientific questions apply across many tectonic settings. Do intrusions exploit pre-existing structures and/or are they focused in the areas of greatest crustal/lithospheric thinning? Does the volume of intrusions in magmatic rifts vary along strike and relate to segmentation at the mid-ocean ridge, or does voluminous magmatism overwhelm focusing mechanisms and result in a more uniform distribution of intrusions along the margin? A 3D seismic velocity model of the crust and uppermost mantle will be built in one of the type examples of magma-rich continental rifting: The Eastern North American Margin (ENAM). The NSF-GeoPRISMS Program supported the collection of active/passive, onshore/offshore seismic data across the ENAM in 2014. As a part of this experiment, data were also collected along and across the East Coast Magnetic Anomaly, which is thought to mark the location of significant synrift magmatism. The data provide excellent 3-D ray coverage of the ENAM area and will be used for 3-D travel time tomography. The resulting velocity model will be used to map the 3-D distribution of magmatic intrusions. This part of the margin is an excellent place to test competing ideas for controls on synrift magmatic addition to the crust.

大陆分裂形成新海洋常常伴随着岩浆的大量喷发。 岩浆可能通过加热和削弱大陆板块而导致大陆分裂。与这些事件相关的火山活动也与地球上的重大灭绝事件有关。尽管岩浆作用在大陆分裂过程中很重要，但人们对裂谷过程中涉及的岩浆作用的总量以及裂谷系统之间的体积如何变化知之甚少。美国东部海岸附近的大陆边缘是世界上与广泛的岩浆作用相关的大陆破裂事件的最佳例子之一。历史上最大的岩浆事件之一发生在盘古大陆破裂和大西洋开放期间。 该项目将分析 2014 年在北卡罗来纳州近海收集的现有海洋地震数据，以量化地壳中冻结的岩浆的体积和分布，以及它与导致破裂的结构之间的关系。该项目支持本科生的培训。岩浆侵入有助于地壳的生长和改变，并强烈影响各种构造环境中的应变局部化。 尽管如此，在构造环境中整个地壳中岩浆侵入体的 3D 分布几乎不存在任何限制，可用于了解对其分布的控制以及地壳改造和变形的后果。 该项目的重点是裂谷中的岩浆作用，但科学问题适用于许多构造环境。入侵是否利用了预先存在的结构和/或它们集中在地壳/岩石圈减薄程度最大的区域？岩浆裂谷中的侵入体体积是否沿走向变化并与大洋中脊的分割有关，或者大量的岩浆活动是否压倒了聚焦机制并导致侵入体沿边缘分布更加均匀？地壳和上地幔的 3D 地震速度模型将在富含岩浆的大陆裂谷的典型例子之一：北美东部边缘 (ENAM) 中建立。 2014 年，NSF-GeoPRISMS 计划支持收集整个 ENAM 的主动/被动、陆上/海上地震数据。作为该实验的一部分，还收集了东海岸磁异常沿线和整个地区的数据，这被认为标志着重要同裂谷岩浆作用的位置。 这些数据提供了 ENAM 区域的出色 3D 射线覆盖，并将用于 3D 行进时间断层扫描。由此产生的速度模型将用于绘制岩浆侵入体的 3D 分布图。这部分边缘是测试控制同裂谷岩浆添加到地壳的竞争想法的绝佳场所。