Seismic wavespeed images across the Iapetus and Tornquist suture zones
Seismic wavespeed images across the Iapetus and Tornquist suture zones
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DOI：
10.1029/2012gl053053
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发表时间：
2012-09
影响因子：
5.2
通讯作者：
Hejun Zhu;E. Bozdağ;D. Peter;J. Tromp
中科院分区：
文献类型：
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作者：
Hejun Zhu;E. Bozdağ;D. Peter;J. Tromp
在加里东造山运动期间，伊阿佩托斯洋和托恩奎斯特海的封闭导致了劳伦西亚、波罗的海和东阿瓦隆尼亚古大陆的碰撞。据推测，这两个闭包的遗迹可能保存在地壳或上地幔。在过去的几十年里，在欧洲西北部收集了许多广角地震剖面，以寻找相关的地下特征。虽然活动源研究揭示了横跨Iapetus和Tornquist缝合带的详细地壳结构，但该地区下方清晰的三维上地幔图像相对较少。我们使用一个新的欧洲地壳和上地幔模型，EU30，确定基于大陆尺度，非线性伴随层析成像，探索上地幔结构在这两个缝合带。模型EU30揭示了两个快速异常的上地幔：一个倾向于西北方向下降到北海下约400公里，和其他倾向于西南方向下降到近250公里的托恩奎斯特缝合带。此外，我们观察到一个“差距”之间的岩石圈劳伦和东部阿瓦隆尼亚的Iapetus缝合带下的不列颠群岛中部。这些地震图像表明，与土卫八海洋和托恩奎斯特海闭合有关的异质性在上地幔中保存了数亿年。
Closures of the Iapetus Ocean and the Tornquist Sea lead to the collision of the paleocontinents of Laurentia, Baltica and Eastern Avalonia during the Caledonian orogeny. It has been speculated that relicts of these two closures may be preserved within the crust or upper mantle. Over the past decades, numerous wide‐angle seismic profiles were gathered in northwestern Europe to search for related subsurface features. Although active source studies revealed detailed crustal structures across the Iapetus and Tornquist suture zones, there are relatively few clear three‐dimensional upper mantle images beneath this region. We use a new European crust and upper mantle model, EU30, determined based on continental scale, nonlinear adjoint tomography, to explore upper mantle structures across these two suture zones. Model EU30 reveals two fast anomalies within the upper mantle: one dips in a northwesterly direction down to approximately 400 km beneath the North Sea, and the other dips in a southwesterly direction down to nearly 250 km across the Tornquist Suture Zone. In addition, we observe a “gap” between the lithospheres of Laurentia and Eastern Avalonia across the Iapetus Suture Zone beneath the central British Isles. These seismic images suggest that heterogeneity related to the closures of the Iapetus Ocean and the Tornquist Sea have been preserved within the upper mantle over hundreds of millions of years.