Mantle dynamics beneath the North Atlantic region from integrated seismic imaging using new regional seafloor data and global datasets

使用新的区域海底数据和全球数据集通过综合地震成像研究北大西洋地区下方的地幔动力学

基本信息

批准号：
NE/X000060/1
负责人：
Sergei Lebedev
金额：
$ 81.02万
依托单位：
University of Cambridge
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2023
资助国家：
英国
起止时间：
2023 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FX000060%2F1
关键词：
Mantle dynamics beneath North Atlantic

项目摘要

Mantle plumes are enigmatic hot upwelling rising from instabilities at Earth's core-mantle boundary. When approaching the surface, they are thought to cause the emplacement of Large Igneous Provinces (LIPs), whose catastrophic volcanism led to mass extinctions through Earth history. Continued ascent of hot material within the plumes' tails is believed to create volcanic hotspots, with continual eruptions over tens of m.y. or more, such as in Iceland. Mantle plumes have been difficult to image seismically, and LIP magmatism is often varied chemically and scattered over thousands of km. This prompted alternative, no-plume explanations for LIP and hotspot volcanism. The properties of mantle plumes (starting with their existence, according to sections of the community) and whether and how they cause LIPs are outstanding, first-order questions of Earth science.The Iceland Plume is a type example of the phenomenon and a subject of long-standing debate. It is thought to cause Iceland's present volcanic activity and the NE Atlantic Ocean's anomalously shallow (per seafloor age) bathymetry. It may also have created the N. Atlantic Igneous Province (NAIP), its ~60 m.y. old volcanic areas dispersed from Britain to western Greenland. Geophysical and petrological data indicate anomalously hot sub-lithospheric mantle below Iceland, and the Iceland and NAIP basalts show isotopic ratios with deep-mantle signatures, consistent with a plume origin.The Iceland Plume was a target of many seismic imaging studies, but the gap in station coverage around Iceland (no stations on the seafloor) translated into major gaps in the data sampling of the mantle. Available seismic models show frustratingly low mutual consistency. The vertical and lateral mantle flow below NE Atlantic is largely unknown. In 2018-20, the project SEA-SEIS, led by the PI, operated Ocean-Bottom Seismometers (OBS) across a large part of NE Atlantic, filling much of the sampling gap. SEA-SEIS' own focus was on structure and seismicity of Ireland's offshore, but the network was designed to also image the Iceland Plume. The proposed project capitalises on the exceptional opportunity of using unique new data (scheduled for public release at SEA-SEIS' end) at no data-collection cost.This project's goal is a breakthrough in our understanding of the structure and dynamics of the Iceland Plume and of how it could cause the NAIP magmatism. This will be achieved by combining the new data with all other relevant seismic data available and applying a suite of complementary imaging methods that will resolve plume structure and plume-induced flow. Seismic tomography with new and all pre-existing data will yield a detailed 3D image of the region's upper and lower mantle. We will combine waveform inversion of surface and regional S waves (sampling the upper mantle) with multi-frequency, teleseismic travel-time tomography (also sampling the lower mantle). The thickness and, by inference, temperature of the mantle transition zone (TZ, ~410-660 km depths) will be mapped using receiver functions (RF). Recent maps show intriguing small-scale variations beneath NE Atlantic but a large gap in the key area between Iceland and Britain. We will fill this gap and expect to learn where and how the hot plume rises through the TZ.Waveform tomography and interstation surface-wave measurements will constrain a lithospheric-thickness map and show whether or not thin-lithosphere channels connect Iceland with NAIP sites to the east.Seismic anisotropy indicates fabric created by flow of the rock at depth. It will be mapped with complementary shear-wave-splitting and surface-wave methods and show current directions of convective flow in the NE Atlantic upper mantle.The combined, integrated evidence will illuminate the Iceland Plume and convective currents it creates in unprecedented detail. It will bring important new insights into the mechanisms of intraplate volcanism globally.

地幔柱是从地球核心-地幔边界的不稳定性中升起的神秘热上升流。当接近地表时，它们被认为会导致大型火成岩省（LIP）的形成，其灾难性的火山活动导致了地球历史上的大规模灭绝。据信，羽流尾部内热物质的持续上升会形成火山热点，并在数十年的时间内持续喷发。或更多，例如在冰岛。地幔柱很难通过地震成像，而且 LIP 岩浆活动通常会发生化学变化，并且分散在数千公里范围内。这促使人们对 LIP 和热点火山活动提出了另一种非羽流解释。地幔柱的特性（根据该群体的说法，从它们的存在开始）以及它们是否以及如何引起 LIP 是地球科学中突出的、首要的问题。冰岛地幔柱是这种现象的一个典型例子，也是该现象的一个主题。长期争论。据认为，冰岛目前的火山活动和东北大西洋的水深异常浅（根据海底年龄）是由它造成的。它还可能创造了北大西洋火成岩省 (NAIP)，其距今约 60 m.y.古老的火山区从英国分散到格陵兰岛西部。地球物理和岩石学数据表明冰岛下方存在异常热的岩石圈下地幔，冰岛和 NAIP 玄武岩显示出具有深部地幔特征的同位素比，与地幔柱起源一致。冰岛地幔柱是许多地震成像研究的目标，但差距冰岛周围的站覆盖范围（海底没有站）转化为地幔数据采样的主要差距。现有的地震模型显示出相互一致性极低，令人沮丧。大西洋东北部下方的垂直和横向地幔流在很大程度上是未知的。 2018-20 年，由 PI 领导的 SEA-SEIS 项目在大西洋东北部的大部分地区运行了海底地震仪 (OBS)，填补了大部分采样空白。 SEA-SEIS 自己的重点是爱尔兰近海的结构和地震活动，但该网络的设计也旨在对冰岛羽流进行成像。拟议的项目利用了使用独特的新数据（计划在 SEA-SEIS 端公开发布）的特殊机会，无需任何数据收集成本。该项目的目标是我们对冰岛羽流结构和动态的理解取得突破。以及它如何导致 NAIP 岩浆活动。这将通过将新数据与所有其他可用的相关地震数据相结合，并应用一套互补的成像方法来解决羽流结构和羽流引起的流动来实现。利用新数据和所有现有数据进行的地震层析成像将生成该地区上地幔和下地幔的详细 3D 图像。我们将把表面和区域 S 波的波形反演（对上地幔进行采样）与多频远震走时断层扫描（对下地幔进行采样）结合起来。将使用接收器函数 (RF) 绘制地幔过渡带（TZ，深度约 410-660 公里）的厚度和推断温度。最近的地图显示了东北大西洋下方有趣的小规模变化，但冰岛和英国之间的关键区域存在巨大差距。我们将填补这一空白，并期望了解热羽流在何处以及如何通过 TZ 上升。波形断层扫描和站间表面波测量将限制岩石圈厚度图，并显示薄岩石圈通道是否将冰岛与 NAIP 地点连接起来东部。地震各向异性表明岩石在深处流动所形成的结构。它将利用互补的剪切波分裂和表面波方法进行绘制，并显示东北大西洋上地幔中对流的当前方向。综合的综合证据将以前所未有的细节阐明冰岛羽流及其产生的对流。它将为全球板内火山作用机制带来重要的新见解。

项目成果

期刊论文数量（8）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Seismic Thermography

地震热成像

DOI：
http://dx.10.1785/0120230245
发表时间：
2024
期刊：
Bulletin of the Seismological Society of America
影响因子：
3
作者：
Lebedev S
通讯作者：
Lebedev S

Structure and evolution of the Australian plate and underlying upper mantle from waveform tomography with massive data sets

通过海量数据集波形断层扫描研究澳大利亚板块和底层上地幔的结构和演化

DOI：
http://dx.10.17863/cam.105703
发表时间：
2023
期刊：
影响因子：
0
作者：
De Laat J
通讯作者：
De Laat J

Determining subsurface temperature & lithospheric structure from joint geophysical-petrological inversion: A case study from Ireland

确定地下温度

DOI：
10.1016/j.tecto.2023.230094
发表时间：
2023-11-01
期刊：
Tectonophysics
影响因子：
2.9
作者：
E. Chambers;R. Bonadio;J. Fullea;Sergei Lebedev;Yihe Xu;D. Kiyan;Christopher J. Bean;Patrick A. Meere;Ben Mather;Brian M. O'Reilly
通讯作者：
Brian M. O'Reilly

Defining Continental Lithosphere as a Layer With Abundant Frozen-In Structures That Scatter Seismic Waves

将大陆岩石圈定义为具有大量散射地震波的冻结结构的层