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

从海底 MT 数据看美国东北部边缘的岩石圈-软流圈边界结构

• 批准号: 1536161
• 负责人: Robert Evans
• 金额: $ 17.4万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-15 至 2017-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1536161&HistoricalAwards=false
• 关键词: Structure; Lithosphere; Asthenosphere; Boundary; Across

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.

北美东部的中部中部地区中部地区是裂谷过程正在进行的研究的重点。该地区提供了了解岩石圈弱点在指导过去大陆裂隙中的作用的机会。目前从大陆壳到海洋壳的过渡，但尚不清楚该目前“被动”边缘的构造板通过从大陆壳到海洋壳的过渡，但尚不清楚地形上的地形以及底层延性地幔的特性。这些信息可以提供有关地球构造板如何随着时间而变化的线索，以及为什么大陆以它们所做的模式破裂。确定岩石圈 - 亚群边界（LAB）仍然有争议，尽管该边界是板块构件范式最基本的方面之一。除了对岩石圈底部地形的知识有限外，板块紧邻板圈的性质的限制也很差。 已经提出了各种解释，以解释边缘的地震观测，包括来自地幔羽流的残余热扰动，含水的上地幔和部分熔体的存在。但是，热扰动模型与岩石圈急剧变薄不一致。这项研究将使用磁铁性数据为问题带来新的限制。将在玛莎（Martha）的葡萄园，马萨诸塞州葡萄园（MA）和陆地上的2个站点上部署的14个海底仪器的数据处理。将根据大流星热点的影响而获得和解释上层柱结构的2D电阻率模型。将研究实验室的深度，深层岩石圈的深度性质以及是否存在在软圈顶部的熔体。