Collaborative Research: Damage Defects and Diffusion of Noble Gases in Minerals: He in Zircon as a Model System

稀有气体(氦、氦、氩、氪、氙气和氡)在了解各种地球和行星过程中发挥着核心作用，从追踪陨石的起源到地幔的分异，再到地质过程的时间和速率。然而，虽然我们现在可以非常精确地测量矿物中的惰性气体，但我们对它们如何结合到矿物中、通过矿物迁移以及如何从矿物中消失的理解是简单化的，在重要方面可能是错误的。这项工作将使用一系列新颖的实验来了解一种矿物-锆石中惰性气体氦的行为，以建立对其他系统中惰性气体行为的一般了解。在具有不同数量和类型的晶体缺陷和晶体取向的锆石样品中测量不同的氦同位素的能力(以及放射性成因氦放射性同位素测年系统的广泛应用)使其成为这项工作的理想模型系统。该项目将专注于产生放射性的4He，以及在重核素反冲和轻离子或中子损伤中原位注入或产生不同数量的辐射损伤的锆石中的3He和4He，并将研究损伤缺陷退火对He行为的影响。这些实验将区分损伤缺陷作为陷阱、曲折增强剂和快速路径在正向和逆行积累的不同水平上的影响。

The noble gases (helium, neon, argon, krypton, xenon, and radon) play a central role in understanding a wide variety of Earth and planetary processes, from tracing the origins of meteorites, to the differentiation of Earth's mantle, to dating the timing and rates of geologic processes. However, while we can now measure noble gases in minerals very precisely, our understanding of how they are incorporated into, migrate through, and are lost from minerals is simplistic and likely wrong in important ways. This work will use a series of novel experiments to understand the behavior of one noble gas, helium, in one mineral, zircon, to build a general understanding of noble gas behavior in other systems.The ability to measure distinct isotopes of helium in zircon specimens with differing amounts and types of crystal defects and crystallographic orientations (as well as the widespread utility of the radiogenic He radioisotopic dating system) make this an ideal model system for this work. The project will focus on radiogenic 4He, as well as 3He and 4He implanted or generated in situ in zircons with varying amounts of radiation damage from both heavy nuclide recoil and light ion or neutron damage, and will also examine the effects of damage defect annealing on He behavior. These experiments will distinguish between the effects of damage defects as traps, tortuosity enhancers, and fast-paths at various levels of pro- and retrograde accumulation.