Mantle Circulation Constrained (MC2): A multidisciplinary 4D Earth framework for understanding mantle upwellings

地幔环流约束 (MC2)：用于理解地幔上升流的多学科 4D 地球框架

基本信息

批准号：
NE/T012501/1
负责人：
Gareth Garmon Roberts
金额：
$ 34.41万
依托单位：
Imperial College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2020
资助国家：
英国
起止时间：
2020 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FT012501%2F1
关键词：
Mantle Circulation Constrained MC2 multidisciplinary

项目摘要

The theory of plate tectonics revolutionised the Earth sciences and had impacts across society, by providing a framework to understand the motion of Earth's surface. However, plate tectonic theory does not tell us about the processes deeper in the Earth that drive plate motions, nor does it explain some of the most dramatic events in Earth history: the breakup of plates and outpouring of huge volumes of lava. The next required breakthrough is to make this leap, from a 2D description of plates to understanding the truly 4D nature of Earth's interior processes.Motion of the Earth's interior, its circulation, involves both upwelling and downwelling. The upwelling flow in the Earth remains enigmatic, occurring in the present-day as both hot focused plumes, which are only just observable through modern seismic imaging techniques, and a hypothesised diffuse flow, which has evaded detection entirely. A third mode of mantle upwelling is currently dormant, making its mantle flow signature unknown. However, this dormant mode of flow drives massive outpourings of lava, and has been associated with continental breakup and mass extinction events.Our project's overall goal is to constrain how mantle upwellings operate within the Earth. We will investigate how plate tectonics is linked to mantle circulation, by combining the history of plate movements across Earth's surface with observations drawn from across the geosciences, and use these to constrain state-of-the-art 4D computational models of mantle flow.These advances are made possible by recent progress in disciplines from across the Earth sciences, expertise we bring together here in geodynamics, seismology, geomagnetism, geochemistry, petrology, and thermodynamics. We will constrain present mantle flow by gathering new seismic imaging data of the Earth's deep interior. We will constrain past mantle flow using newly collected data on the mantle's composition, past magnetic field, and the history of Earth's surface uplift. We will use these multidisciplinary approaches to generate the most spatially and temporally complete set of observational constraints on mantle circulation yet assembled.These observations will be used to constrain and improve models that calculate mantle circulation in an Earth-like 3D geometry, driven by plate motion histories (mantle circulation models, MCMs). This is a timely development capitalising on the only recently available record of plate motion over 1 billion years of Earth History. The MCMs predict the mantle's temperature, density, and velocity through time, providing a 4D model of the Earth. Uncertain inputs in these models such as mantle viscosity and composition will be investigated within the bounds provided by the project's geochemical and thermodynamic work packages that will develop new models of Earth's high pressure mineralogy and physical properties. We will test the present-day predictions of the MCMs by converting model outputs to predict density and material properties within the Earth, using our developments on mineral physics modelling. With these inputs and constraints, we will create the first accurate computational models of mantle circulation over the last 1 billion years, which will provide dynamical insight into what drives the diversity of upwellings in the Earth.This tightly integrated multidisciplinary project is absolutely essential to achieve the best constrained MCMs and advance our understanding of Earth's interior processes. The result will be a coherent mantle circulation record of one quarter of Earth's history, and a major advance in our understanding of how mantle upwellings have impacted planetary evolution over this period.

板块构造理论通过提供理解地球表面运动的框架，彻底改变了地球科学，并对整个社会产生了影响。然而，板块构造理论并没有告诉我们地球深处驱动板块运动的过程，也没有解释地球历史上一些最戏剧性的事件：板块的破裂和大量熔岩的涌出。下一个需要的突破是实现这一飞跃，从板块的 2D 描述到理解地球内部过程的真正 4D 性质。地球内部的运动及其循环涉及上升流和下降流。地球上的上升流仍然是个谜，在当今，它既表现为热聚焦羽流（只能通过现代地震成像技术观察到），也表现为假设的扩散流（完全无法检测到）。第三种地幔上升模式目前处于休眠状态，使其地幔流特征未知。然而，这种休眠的流动模式会导致熔岩大量涌出，并与大陆破裂和大规模灭绝事件有关。我们项目的总体目标是限制地幔上升流在地球内的运作方式。我们将通过将地球表面板块运动的历史与整个地球科学的观测结果相结合，研究板块构造如何与地幔循环联系起来，并利用这些来约束最先进的地幔流 4D 计算模型。地球科学各个学科的最新进展，以及我们在地球动力学、地震学、地磁学、地球化学、岩石学和热力学方面汇集的专业知识，使这些进步成为可能。我们将通过收集地球内部深处的新地震成像数据来限制当前的地幔流。我们将使用新收集的有关地幔成分、过去磁场和地球表面隆起历史的数据来限制过去的地幔流。我们将使用这些多学科方法来生成迄今为止在空间和时间上最完整的地幔循环观测约束集。这些观测结果将用于约束和改进计算由板块运动驱动的类地 3D 几何中的地幔循环的模型历史（地幔循环模型，MCM）。这是一项及时的发展，利用了地球历史上 10 亿年板块运动的最新可用记录。 MCM 可预测地幔随时间的温度、密度和速度，提供地球的 4D 模型。这些模型中的不确定输入，例如地幔粘度和成分，将在该项目的地球化学和热力学工作包提供的范围内进行研究，该工作包将开发地球高压矿物学和物理性质的新模型。我们将利用我们在矿物物理建模方面的进展，通过转换模型输出来预测地球内的密度和材料特性，来测试 MCM 的当前预测。有了这些输入和约束，我们将创建过去 10 亿年来第一个准确的地幔循环计算模型，这将为驱动地球上涌的多样性提供动态见解。这个紧密结合的多学科项目对于实现这一目标绝对必要。最好的约束 MCM 并增进我们对地球内部过程的理解。其结果将是地球四分之一历史的连贯地幔循环记录，也是我们对这一时期地幔上升流如何影响行星演化的理解的重大进展。