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

世界各地的前寒武纪盾牌包含地球上最古老的岩石，因此，它们是我们理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改的细节构成了我的研究的主要重点。我的研究计划建议继续研究一个新发现的古老地壳（38亿耳：Ga），它是地球上最古老的地壳之一。这个古老的地壳位于北方魁北克（Inukjuak地区）的加拿大地盾，在研究这个地壳时，我们可以对地球地质演化的一些基本问题提出限制;例如：大陆开始形成的方式和原因？地球的地幔是以类似于月球和火星的方式演化的（行星演化）还是遵循不同的路径（陆地演化）。来自大洋岛屿和洋脊的岩石表明，现今地幔由贫化和富集的储层组成。这些不同的储层是如何形成的？后一个问题的答案正在解决的同位素研究的蒙特勒吉安山在西南魁北克。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循环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，以研究北极冰层融化对海洋环流的影响。这项工作将通过结合地质实地研究和实地收集的岩石的地球化学和同位素分析（Lu-Hf、Sm-Nd、Rb-Sr）进行。野外研究将限制Inukjuak地区岩石的变形、变质和地层的程度。分析研究将限制岩石的来源。这些项目的资金将在5年内为4名研究生提供支持，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.