Structure of the Lithosphere - Asthenosphere Boundary Across the Northeastern US Margin from Seafloor MT Data

北美洲东部边缘的中大西洋中部地区是正在进行的裂谷过程研究的重点。该地区提供了一个机会，以了解先前存在的岩石圈弱点在指导过去的大陆裂谷的作用。在这个目前的“被动”边缘的构造板块通过从大陆地壳到海洋地壳的过渡变薄，但在板块的基础上的地形细节，以及下面的韧性地幔的属性是未知的。这些信息可以提供关于地球构造板块如何随时间演化的线索，以及为什么大陆会以这样的模式分裂。岩石圈-软流圈边界（LAB）的确定仍然存在争议，尽管该边界是板块构造范式中最基本的方面之一。除了对岩石圈底部地形的有限了解外，对板块下方最上层软流圈性质的限制也很差。 人们提出了各种解释来解释整个边缘的地震观测，包括地幔柱的残余热扰动，含水上地幔和部分熔融的存在。然而，热扰动模型是不一致的岩石圈显着减薄。这项研究将使用大地电磁数据带来新的约束问题。将完成对部署在马萨诸塞州玛莎葡萄园岛近海大陆架上的14个海底仪器和2个陆地站的数据处理。将获得上地幔结构的二维电阻率模型，并根据大流星热点的影响引起的岩石圈蚀变进行解释。LAB的深度，更深的大陆岩石圈的性质，以及是否熔融存在于软流圈的顶部将被调查。

The central mid-Atlantic region of the eastern North America margin is the focus of ongoing studies of rift processes. The region presents the opportunity to understand the role of pre-existing lithospheric weakness in guiding past continental rifting. The tectonic plate at this currently 'passive' margin thins through the transition from continental to oceanic crust, yet details of the topography on the base of the plate, as well as the properties of the underlying ductile mantle are not known. This information can provide clues about how Earth's tectonic plates evolve over time and why continents break up in the pattern that they do.Determination of the lithosphere-asthenosphere boundary (LAB) remains controversial, despite this boundary being one of the most fundamental aspects of the plate tectonics paradigm. In addition to limited knowledge about the topography on the base of the lithosphere, constraints on the properties of the uppermost asthenosphere immediately beneath the plate, are poor. Various interpretations have been presented to explain seismic observations across the margin, including a remnant thermal perturbation from a mantle plume, a hydrous upper mantle and the presence of partial melt. However, the thermal perturbation model is not consistent with a dramatically thinned lithosphere. This study will use magnetotelluric data to bring new constraints to the problem. Processing of data from 14 seafloor instruments deployed across the continental shelf offshore Martha's Vineyard, MA, and 2 stations on land will be accomplished. A 2-D resistivity model of the upper-mantle structure will be obtained and interpreted in terms of lithospheric alteration resulting from the influence of the Great Meteor hotspot. The depth to the LAB, the nature of the deeper continental lithosphere and whether melt is present at the top of the asthenosphere will be investigated.