Chemical heterogeneities in the early Earth and planetary analogues: their formation, preservation and destruction

地球和行星科学的一个基本问题是行星是如何形成的，以及它们是如何随着时间的推移而演变的。地球化学和数值模型，以及类似的行星模型表明，地球是由复杂的加工物质吸积而成，然后在形成后迅速进化。早期的事件，如地核分离、地幔分化和地壳形成，似乎是在地球增生后不久发生的。此外，在地球形成的最后阶段，物质的不断增加改变了地幔的组成。在过去的几年里，短寿命同位素计时器的发展使得对地球增生后不久发生的事件进行年代学研究成为可能。通过地幔对流和与板块构造相关的地壳再循环的混合，减弱了原始地幔非均质性的强度。然而，太古宙早期形成的同位素变化的最新文献表明，原始化学储层持续存在了100 - 10亿年。******在接下来的五年里，我的研究计划将集中在涉及地球和行星科学的三个关键问题上：***1)影响早期地幔化学成分的主要事件的性质和时间是什么？***2)早期形成的化学非均质在对流地幔中存在了多长时间？早期地球的对流类型是什么？***3)地球的早期进化与其他类似的行星（如灶神星）相似吗？******该研究项目重点关注灭绝和长寿命放射性同位素系统数据的开发、改进和获取，以及不同行星物质的亲铁元素丰度。这些地球化学工具非常适合约束地核和地幔的早期演化，并研究晚期增生添加的时间和化学后果。该项目的发现将有助于改进地球早期发展阶段的内部动力学模型，并提供有关加拿大北部最古老地形的地质知识。这个研究项目是为几个本科生和四个研究生设计的，他们将获得一套与学术界和工业界相关的独特技能

A fundamental question in Earth and planetary sciences is how the planets formed and how they evolved through time. Geochemical and numerical models, as well as planetary analogs suggest that Earth accreted from complex processed materials and then evolved rapidly after its formation. Early events such as core segregation, mantle differentiation and crust formation seem to have occurred shortly after the Earth's accretion. Furthermore, the composition of the Earth's mantle was modified by the continued accretion of materials during the final stages of formation. In the past few years, the development of short-lived isotopic chronometers has allowed chronological studies of the events that followed shortly the Earth's accretion. Mixing through mantle convection and crustal recycling associated with plate tectonics has attenuated the magnitude of primordial mantle heterogeneities. However, recent documentation of early-formed isotope variations in Archean rocks requires the persistence of primordial chemical reservoirs for > 1 billion years. ******Over the next five years my research program will focus on three key problems involving Earth and planetary sciences:***1) What are the nature and timing of the major events affecting the chemical composition of the early Earth's mantle?***2) How long did early-formed chemical heterogeneities survive in the convective mantle, and what was the style of convection of the early Earth?***3) Is the early evolution of the Earth comparable to other planetary analogues like the asteroid Vesta?******This research program is strongly focused on the development, improvement and acquisition of data from extinct and long-lived radioactive isotope systematics, as well as obtaining siderophile element abundances for different planetary materials. These geochemical tools are ideal to constrain core and mantle early evolution, and investigate the timing and chemical consequences of late accretionary additions. The findings of this project will help to improve models of the internal dynamics of the Earth during its early stages of development, and provide geological knowledge about the oldest terrains in northern Canada. This research program is designed to involve several undergraduate and four graduate students who will acquire a unique set of skills that are relevant to both academia and industry.**