- MSI 1302
Title: Constraining past Earth and planetary surface temperatures using cosmogenic noble gases
Abstract: Cosmogenic nuclides, which are produced in the uppermost few meters of the Earth’s crust by cosmic-ray particle interactions with atomic nuclei, are commonly used to quantify the rates and timing of surface processes on Earth and other planets. Some of the first terrestrial cosmogenic nuclide measurements revealed that the cosmogenic noble gases 3He and 21Ne are diffusively lost at Earth surface temperatures in common silicate minerals like quartz and feldspars. Viewed as a fatal limitation for geologic applications since then, the open-system behavior of cosmogenic noble gases can, in fact, be exploited to quantitatively reconstruct temperatures at the surfaces of Earth and other planetary bodies. In this talk, I will describe the theoretical framework for using cosmogenic noble gases as a paleother-mometer based on the principles and mathematics underlying radiogenic noble gas thermochronometry. I will then present results of experimental work to quantify the kinetics of helium and neon diffusion in quartz and feldspars. These experiments reveal that, in general, cosmogenic 3He–in–quartz measurements can be used to constrain past surface temperatures at high latitudes and elevations, while 21Ne–in–feldspar measurements can be used to constrain past surface temperatures at lower latitudes and elevations, and on other planetary bodies. In detail, 3He and 21Ne diffusion kinetics vary significantly across samples of different geologic origin, necessitating sample-specific diffusion kinetics for quantitative applications. Having laid out the theoretical and experimental backbone of cosmogenic noble gas paleothermometry, I will present a suite of ongoing and future applications of the technique to problems in paleoclimate and planetary science.