Modification of Crust and Mantle Lithosphere Beneath the Southern Part of the Eastern North American Passive Margin
Modification of Crust and Mantle Lithosphere Beneath the Southern Part of the Eastern North American Passive Margin
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北美东部被动边缘南部地壳和地幔岩石圈的改造
DOI：
10.1029/2020gl090555
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发表时间：
2021-08
影响因子：
5.2
通讯作者：
Cong Li;Haiying Gao
中科院分区：
文献类型：
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作者：
Cong Li;Haiying Gao
北美东部被动边缘受到中生代裂谷作用的影响。最近部署的陆上和海上台站的地震数据为研究岩石圈结构的同裂和后裂特征提供了独特的机会。使用全波环境噪声层析成像，我们构建了一个新的地震速度模型的岩石圈的美国东南部。我们的模型证实了横跨海岸线的170公里宽的区域内存在着一个海洋-大陆过渡地壳。我们的模型揭示了（a）在这个过渡地壳下面有一片低于平均水平的地幔岩石圈速度，（B）在弗吉尼亚火山下面的地幔岩石圈中有一个低速柱。我们认为异常1代表了在230 Ma左右的裂谷初始阶段位于变薄地壳之下的冷却富集地幔。异常2可能有一个更近的起源在始新世，可能是由于软流圈上涌引起的局部岩石圈脱层。
The eastern North American passive margin was modified by Mesozoic rifting. Seismic data from recent deployment of onshore and offshore stations offer a unique opportunity for studying the signature of syn‐rifting and postrifting in lithospheric structures. Using full‐wave ambient noise tomography, we construct a new seismic velocity model for the lithosphere of the southeastern United States. Our model confirms an oceanic‐continental transitional crust over a ∼70 km wide zone across the coastline. Our model reveals (a) a patch of lower‐than‐average mantle lithospheric velocities underlying this transitional crust and (b) a low‐velocity column in the mantle lithosphere beneath the Virginia volcanoes. We propose that anomaly 1 represents cooled enriched mantle that underplated the thinning crust during the initial stages of rifting around 230 Ma. Anomaly 2 likely has a more recent origin in the Eocene and may result from an asthenospheric upwelling induced by a localized lithospheric delamination.