New advances in Ar-Ar geochronology and novel applications to global tectonics

最有用的岩石定年方法之一是基于钾（40 K）到氩（40 Ar）的放射性衰变，它在地质和天文时间的巨大跨度中充当长寿的时钟。氩-40/氩-39（Ar-Ar）定年技术是K-Ar年代学方法的一种变体，是了解世界各地地质演化的最有用的定年工具之一。然而，要理解我们获得的Ar-Ar年龄的意义，需要详细了解气态Ar原子是如何通过它们聚集的岩石和晶体扩散的。晶体结构、矿物化学、溶解度和晶体结构中缺陷的存在等许多因素控制着扩散行为，它们的影响将通过最常见的造岩和测年矿物之一的实验室实验和数值模拟来研究-云母。使用不同类型的云母上的各种分析技术的实验可能会导致一个新的范例Ar在矿物中的扩散，因此，我们测量的年龄更准确的解释。最近的研究表明，我们的知识的准确性和精确度的40 K到40 Ar的衰变率需要提高;在第二个相关的主题，独特的实验提出了将测量从第一原则的原位40 Ar衰变率产生的人工富集40 K源。这将使Ar-Ar年龄与其他地质年代学系统的年龄进行更准确的比较。人们普遍认为，超级大陆的形成对地壳、大气、气候和生命的演化有着深远的影响。拟议研究的最后一个主题将应用上述知识对导致最新超级大陆Pangea形成的机制进行急需的年龄限制，提供一个模板，可以评估更古老的超级大陆的起源，并解决我们对指导地球最近地质演化的主要全球构造力量的知识中的根本差距。该研究计划将在拟议的资助期间培训至少3名博士生，4名硕士生和5名研究助理。

One of the most useful methods of dating rocks is based on the radioactive decay of potassium (40K) to argon (40Ar), which serves as a long-lived clock over the vast span of geologic and astronomic time. The argon-40 / argon-39 (Ar-Ar) dating technique - a variant of the K-Ar geochronological method - is one of the most useful dating tools in understanding the geological evolution of regions around the world. Understanding the significance of the Ar-Ar ages we obtain, however, requires a detailed understanding of how the gaseous Ar atoms diffuse through the rocks and crystals in which they accumulate. Many factors such as crystal structure, mineral chemistry, solubility, and the presence of defects in the crystal structure control diffusional behaviour, and their effects will be studied through laboratory experiments and numerical modelling in one of the most common rock-forming and dated mineral types - the micas. Experiments using various analytical techniques on different types of mica may lead to a new paradigm for Ar diffusion in minerals and thus, a more accurate interpretation of the ages that we measure. Recent studies have shown that our knowledge of the accuracy and precision of the decay rate of 40K to 40Ar needs to be improved; in a second related theme, unique experiments are proposed which will measure from first principles the in-situ 40Ar decay rate produced from an artificially enriched 40K source. This will enable more accurate comparisons of Ar-Ar ages with ages from other geochronological systems. The formation of supercontinents is widely accepted to have a profound effect on the evolution of the Earth's crust, atmosphere, climate, and life. A final theme of the proposed research will apply the above knowledge to place much-needed age constraints on the mechanisms that led to the formation of the latest supercontinent, Pangea, provide a template by which the origin of older supercontinents can be evaluated, and address a fundamental gap in our knowledge of the major global tectonic forces that have guided the Earth's recent geological evolution. This research program will train at least 3 PhD students, 4 MSc students and 5 research assistants over the duration of the proposed funding.