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

大陆裂解形成新的海洋往往伴随着岩浆活动的大量涌出。 岩浆可能通过加热和弱化大陆构造板块而导致大陆裂解。与这些事件相关的火山活动也与地球上的主要灭绝事件有关。尽管岩浆活动在大陆裂解过程中的重要性，但人们对裂谷过程中所涉及的岩浆活动总量以及裂谷系统之间的岩浆活动量如何变化知之甚少。美国东部海岸外的大陆边缘是世界上与广泛岩浆活动有关的大陆分裂事件的最好例子之一。历史上最大的岩浆事件之一发生在泛古大陆分裂和大西洋开放期间。 该项目将涉及分析2014年在北卡罗来纳州近海边缘收集的现有海洋地震数据，以量化地壳中冻结的岩浆的数量和分布，以及它与导致破裂的结构之间的关系。该项目支持培养一名本科生：岩浆侵入体有助于地壳的生长和改变，并对各种构造环境中的应变局部化产生重大影响。 尽管如此，很少有限制存在的3-D分布的岩浆侵入体在整个地壳中的构造环境，可以用来了解其分布的控制和地壳改造和变形的后果。 这个项目的重点是裂谷中的岩浆活动，但科学问题适用于许多构造环境。侵入体是否利用了预先存在的结构和/或它们是否集中在地壳/岩石圈减薄最严重的地区？岩浆裂谷中侵入体的体积是否沿着走向变化并与洋中脊的分段有关，还是大量岩浆活动压倒了聚焦机制并导致侵入体沿着边缘分布更均匀？本文以富含岩浆大陆裂谷作用的典型范例之一--北美大陆边缘东部（ENAM）为例，建立了地壳和上地幔的三维地震速度模型。 2014年，国家科学基金会GeoPRISMS计划支持在ENAM收集主动/被动、陆上/海上地震数据。作为这项实验的一部分，数据也收集了沿着和横跨东海岸磁异常，这被认为是标志着显着的同生裂谷岩浆活动的位置。 这些数据提供了极好的三维射线覆盖的ENAM地区，并将用于三维旅行时间层析成像。由此产生的速度模型将用于绘制岩浆侵入体的三维分布图。这部分边缘是一个很好的地方来测试控制地壳同生裂谷岩浆的竞争性想法。

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.