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

板块构造理论通过提供一个了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，板块构造理论没有告诉我们地球更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：板块破裂和大量熔岩涌出。下一个需要的突破是实现这一飞跃，从对板块的2D描述到理解地球内部过程的真正4D本质。地球内部的运动，即其循环，既涉及上升流，也涉及下行流。地球中的上升流仍然是个谜，在今天既有热的聚焦羽流，只有通过现代地震成像技术才能观察到，也有假想的扩散流，完全躲过了探测。地幔上升的第三种模式目前处于休眠状态，这使得其地幔流动特征未知。然而，这种休眠的流动模式驱动了大量的熔岩喷发，并与大陆分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涌在地球内的运作方式。我们将研究板块构造是如何与地幔环流联系在一起的，通过结合地球表面板块运动的历史和来自地球科学的观测，并利用这些来约束最先进的地幔流动的4D计算模型。这些进展是由于来自地球科学的学科的最新进展，我们在这里汇集了地球动力学、地震学、地磁学、地球化学、岩石学和热力学的专业知识。我们将通过收集新的地球深部地震成像数据来限制目前的地幔流动。我们将使用新收集的关于地幔成分、过去的磁场和地球表面隆起历史的数据来限制过去的地幔流动。我们将使用这些多学科方法来生成迄今组装的对地幔环流在空间和时间上最完整的观测约束集。这些观测将被用来约束和改进由板块运动历史(地幔环流模型)驱动的、在类似地球的3D几何中计算地幔环流的模型。这是一个及时的发展，利用了最近唯一可获得的超过10亿年地球历史的板块运动记录。MCMS预测地幔的温度、密度和随时间变化的速度，提供了地球的4D模型。这些模型中的不确定输入，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调查，这些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发展，通过转换模型输出来预测地球内的密度和材料特性，从而测试MCMS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环流计算模型，这将提供对地球上升流多样性驱动因素的动力学洞察。

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.