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.

北美东部边缘的大西洋中部地区是裂谷过程持续研究的重点。该地区提供了了解先前存在的岩石圈弱点在引导过去大陆裂谷中的作用的机会。目前这个“被动”边缘的构造板块在从大陆地壳到海洋地壳的过渡过程中变薄，但板块底部的地形细节以及下面的韧性地幔的特性尚不清楚。这些信息可以提供有关地球构造板块如何随时间演变以及大陆为何以这种方式分裂的线索。岩石圈-软流圈边界 (LAB) 的确定仍然存在争议，尽管该边界是地球构造最基本的方面之一。板块构造范式。除了对岩石圈底部地形的了解有限之外，对紧邻板块下方的最上层软流圈特性的限制也很有限。 人们提出了各种解释来解释边缘的地震观测结果，包括地幔柱的残余热扰动、含水的上地幔和部分熔融的存在。然而，热扰动模型与急剧变薄的岩石圈并不一致。这项研究将利用大地电磁数据为该问题带来新的约束。将对来自部署在马萨诸塞州玛莎葡萄园岛近海大陆架的 14 个海底仪器和 2 个陆地站的数据进行处理。将获得上地幔结构的二维电阻率模型，并根据大流星热点影响引起的岩石圈蚀变进行解释。将调查 LAB 的深度、更深的大陆岩石圈的性质以及软流圈顶部是否存在融化。