Diamonds and their inclusions as thermometers and clocks; deep carbon records the evolution of the lithosphere

大陆和岩石圈地幔是古老的，历史复杂，但关键是它们可以记录地球动力学演化的关键发展。例如，它们可以追踪与地幔温度升高相关的大范围部分熔融的时期，或者通过冷海洋岩石圈的吸积来了解俯冲开始的时间。因此，一个强大的方法来提取岩石圈的热历史将使我们能够区分这些模型。金刚石中的氮缺陷，特别是这些缺陷随时间和温度的演化，长期以来一直被用来估计金刚石在地幔中的停留温度。最近，我们已经开发出一种更复杂的方法，结合钻石包裹体的放射性测年，使我们能够计算长期长期的长期加热或冷却速率的钻石岩石圈，可用于评估热和地球动力学模型的岩石圈的演化。该项目的总体目标是建立世界各地大陆岩石圈形成和随后演化的模式。我们可以获得来自加拿大，澳大利亚，南部非洲，西伯利亚和南美洲的独特钻石收藏，并在需要时获得其他钻石，因此可以应用我们的方法来获得岩石圈演化的全球概况。其基本思想是使用放射性同位素测定环带金刚石中的包裹体，然后观察金刚石晶格中氮缺陷的演化（见背景阅读），以模拟金刚石及其宿主岩石圈地幔的热历史。这需要表征和选择正确的包裹体，一些新的同位素地球化学和代码开发，以模拟缺陷聚集和提取热历史。因此，随着项目的进展，学生可能希望如何专业化有很大的灵活性。

Project Background The continents and associated lithospheric mantle are old with complicated histories but critically they can record key developments in the geodynamic evolution of the Earth. For example, they may track periods of extensive partial melting associated with elevated mantle temperatures or provide insights into the timing of the beginning of subduction through the accretion of cool oceanic lithosphere. Therefore, a robust method to extract the thermal history of the lithosphere would allow us to distinguish such models. Nitrogen defects in diamonds and specifically, the time and temperature-dependent evolution of these defects has long been used to estimate the residence temperature of diamonds in the mantle. Recently we have developed a more sophisticated approach for zoned diamonds which, in combination with radiometric dating of diamond inclusions, enables us to calculate long-term secular heating or cooling rates for diamond-containing lithosphere that can be used to evaluate thermal and geodynamic models for the evolution of the lithosphere. Project Aims and Methods The overall aim of the project is to establish the mode of formation and subsequent evolution of continental lithosphere in different localities around the world. We have access to a unique collection of diamonds from Canada, Australia, Southern Africa, Siberia and South America and have the connections to obtain others if required, so can apply our approach to gain a global overview of lithospheric evolution. The basic idea is to date inclusions in zoned diamonds using radiogenic isotopes, then look at the evolution of nitrogen defects within the diamond lattice (see background reading) to model the thermal history of the diamonds and their hosting lithospheric mantle. This requires characterising and selecting the right inclusions, some novel isotope geochemistry and code development to model the defect aggregation and extract the thermal history. There is therefore quite a lot of flexibility in how the student might wish to specialise as the project progresses.