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

地幔羽流是一种神秘的热上升流，源于地球核幔交界处的不稳定。当接近地表时，它们被认为导致了大型火成岩省(LIP)的侵位，其灾难性的火山作用导致了地球历史上的大规模灭绝。羽流尾部热物质的持续上升被认为是形成火山热点的原因，火山持续喷发的时间长达数十英里。或者更多，比如在冰岛。地幔热柱很难在地震中成像，而且嘴唇的岩浆活动通常是不同的，分散在数千公里的范围内。这促使人们对嘴唇和热点火山作用做出了替代的、没有羽流的解释。地幔热柱的性质(根据社区的某些部分，从它们的存在开始)以及它们是否以及如何造成嘴唇是地球科学的突出的首要问题。冰岛热柱是这种现象的典型例子，也是一个长期争论的主题。它被认为是造成冰岛目前的火山活动和东北大西洋异常浅的(根据海底年龄)测深的原因。它也可能创造了北大西洋火成岩省(NAIP)，它的大约60英里。古老的火山区从英国散布到格陵兰岛西部。地球物理和岩石学数据表明，冰岛下方的岩石圈下地幔异常热，冰岛和奈普玄武岩的同位素比值具有深地幔特征，与地柱起源一致。冰岛羽流是许多地震成像研究的目标，但冰岛周围台站覆盖的差距(海底没有台站)导致了地幔数据采样的重大差距。现有的地震模型显示相互一致性低得令人沮丧。东北大西洋以下的垂直和横向地幔流动在很大程度上是未知的。2018-2020年，由PI领导的SEA-SEIS项目在东北大西洋的大部分地区运行了海底地震仪(OBS)，填补了大部分抽样空白。SEA-SEIS本身的重点是爱尔兰近海的结构和地震活动，但该网络的设计也是为了拍摄冰岛羽流的图像。拟议的项目利用了使用独特的新数据(计划在海上公开发布)的特殊机会，无需支付数据收集成本。该项目的目标是突破我们对冰岛羽流的结构和动力学以及它如何导致NAIP岩浆作用的理解。这将通过将新数据与现有的所有其他相关地震数据结合起来，并应用一套互补的成像方法来解决烟柱结构和烟柱诱导的流动，从而实现这一点。使用新的和所有预先存在的数据的地震层析成像将产生该地区上、下地幔的详细3D图像。我们将结合地表和区域S波的波形反演(采样上地幔)和多频率远震走时层析成像(也采样下地幔)。将使用接收函数(RF)绘制地幔过渡带(TZ，约410-660公里深)的厚度和温度。最近的地图显示了大西洋东北部有趣的小范围变化，但冰岛和英国之间的关键地区存在很大差距。我们将填补这一空白，并期待了解热烟柱在哪里以及如何通过TZ上升。波形层析和台间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站点连接在东部。地震各向异性表明岩石在深处流动所产生的组构。它将用互补的剪切波分裂和面波方法绘制地图，并显示东北大西洋上地幔对流的流向。综合综合的证据将以前所未有的详细程度阐明冰岛羽流和它创造的对流。它将为全球板内火山作用的机制带来重要的新见解。

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.