The interpretation of any noble gas observation made in a solid material depends upon detailed knowledge of that material’s retention characteristics.  For instance, in cosmogenic nuclide studies, it is critical to establish whether all of the cosmogenic atoms still remain in the measured material today, or if diffusive loss needs to be considered. 

A rigorous way to establish noble gas retentivity at a given temperature is through stepped-heating degassing experiments.  Proton-induced noble gases are good analogs for natural cosmogenic species and enable controlled experiments to be performed. 

In the first of these studies, Ken Farley (CIT) and I quantified diffusion kinetics of proton-induced ²¹Ne, ³He and ⁴He in inclusion-free quartz.  Our findings confirmed empirical observations that quartz quantitatively retains ²¹Ne but poorly retains ³He at Earth’s surface conditions.  The experimental approach quantifies fundamental parameters which help constrain the physics of this phenomenon.  We are currently studying diffusion of ²¹Ne and ³He in zircon and plagioclase.  This work is part of a larger study to develop a general understanding of solid state noble gas diffusivity.  Learn more here.