Investigating the Exposure and Thermal History of Enstatite (E) Chondrites and Improving Cosmogenic Noble Gas Production Rate Calculations for Terrestrial and Extraterrestrial Applications

<p dir="ltr">Cosmogenic nuclides can be used to quantify the surface exposure timescales and recent thermal histories of terrestrial and extraterrestrial surfaces. In this dissertation, I develop methods to improve cosmogenic nuclide production rate calculations on Earth and in space, as well as apply cosmogenic noble gases to better understand the histories of meteorites. The study of terrestrial surfaces can be used to inform our understanding of landscape feedbacks with regional tectonics, paleoclimate, and magmatic systems. As surface exposure studies extending beyond the Quaternary become more prevalent, improving our calculations of cosmogenic nuclide production rates through deep time is critical. We find incorporating temporal variations in Earth’s magnetic field are important when calculating pre-Quaternary cosmogenic nuclide production rates, and can significantly affect calculated surface exposure ages. In extraterrestrial applications, identifying non-destructive techniques to quantify subsample composition and improve cosmogenic nuclide production rate estimates are needed to better constrain the exposure ages of meteorites. We used μCT to quantify the abundance of major mineral phases in enstatite (E) chondrites, and found heterogeneously distributed metal in E chondrite subsamples can necessitate substantially different cosmogenic noble gas production rates. When utilizing cosmogenic noble gases to quantify long duration cosmic ray exposure ages, ³He is often considered an unreliable chronometer because it is diffusively lost from meteorites. We quantified the diffusion kinetics of ³He in the major minerals of E chondrites to leverage discrepancies between newly measured ³He and ²¹Ne cosmic ray exposure ages, and constrain the thermal histories of three E chondrites. This combination of subsample-specific cosmogenic noble gas production rates, experimentally-derived diffusion kinetics of ³He in major minerals E chondrites, and cosmogenic noble gas measurements demonstrates ³He is a suitable thermochronometer for E chondrites, and can be used to constrain the thermal histories of meteorites during their exposures to cosmic rays in the space environment.</p>