Origins of the mantle and crust: Isotopic studies from an adolescent earth

世界各地的前寒武纪地盾包含着地球上最古老的岩石，因此，它们是我们了解地球地幔和大陆地壳形成和演化的核心。大陆的生长和稳定以及海洋盆地的形成也代表了地球与太阳系其他岩石行星之间的根本区别。大陆地壳和地幔的初始形成和随后的修正的细节构成了我研究的主要重点。我的研究计划是继续研究新发现的古地壳（38亿年前），它是地球上最古老的地壳之一。这个古老的地壳位于魁北克北部的加拿大地盾（Inukjuak地区），通过研究这个地壳，我们可以对地球地质演化的一些基本问题施加限制；例如：大陆是如何以及为什么开始形成的？地球的地幔是否以与月球和火星相似的方式进化（行星进化），还是遵循不同的路径（陆地进化）？来自海洋岛屿和洋脊的岩石表明，今天的地幔由枯竭和富集的储层组成。这些不同的储层是如何形成的？后一个问题的答案正在魁北克省西南部蒙特雷吉亚山的同位素研究中得到解决。研究加拿大地盾的同位素组成也使我们能够通过过去的冰川旋回来限制北大西洋沉积物来源的变化。同样的技术也可以应用于北冰洋，以研究北冰洋冰盖融化对海洋环流变化的影响。这项工作将通过地质实地研究和地球化学以及对实地收集的岩石进行同位素分析（Lu-Hf, Sm-Nd, Rb-Sr）的结合来进行。野外研究将限制因努克地区岩石的变形程度、变质作用和地层。分析研究将确定岩石的来源。这些项目的资助将为4名研究生提供5年的支持、培训和研究费用。

The Precambrian Shields around the world contain the oldest rocks on the planet and as such, they lie at the heart of our understanding of the formation and evolution of our planet's mantle and continental crust. The growth and stabilization of the continents and formation of the ocean basins also represent a fundamental difference between the Earth and other rocky planets of the solar system. The details of the initial formation and subsequent modification of the continental crust and mantle constitute the principal focus of my research. My research program proposes to continue the study a newly discovered tract of ancient crust (3.8 billion ears: Ga) that rates among the oldest on the planet. This old crust is located in the Canadian Shield of northern Quebec (Inukjuak region) and in studying this crust we can place constraints on some of the fundamental questions of our planet's geological evolution; such as: How and why did continents begin forming? Did the Earth's mantle evolve in a similar fashion as those of the Moon and Mars (a planetary evolution) or follow different path (a terrestrial evolution). Rocks from oceanic islands and ocean ridges indicate that the present day mantle consists of depleted and enriched reservoirs. How were these different reservoirs generated? The answer to this latter question is being addressed in an isotopic study of the Monteregian Hills in SW Quebec. Studying the isotopic composition of the Canadian Shield has also allowed us to constrain changes in the source of sediments to the North Atlantic Ocean through past glacial cycles. The same technique can be applied to the Arctic Ocean to study the effects of changes in oceanic circulation as a result o melting the Arctic ice pack. This work will be carried out through a combination of geological field studies and geochemical and isotopic analyses (Lu-Hf, Sm-Nd, Rb-Sr) of the rocks collected in the field. The field studies will constrain the degree of deformation, metamorphism and stratigraphy of the rocks in the Inukjuak region. The analytical studies will constrain the sources of the rocks. Funding for these projects will provide support, training and research costs for 4 graduate students over 5 years.