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.
