Improved Constraints on Mantle and Crustal Source Signals in CO2 well gases: New Insights from Ultra-high Precision Noble Gas and Clumped Isotope Measurements

Volatile elements (like carbon, nitrogen, oxygen, water, and other gases) are critical for life on Earth. But there are still many open questions about how Earth formed, where volatile elements originated from, and how they move between the atmosphere, oceans, and Earth’s deep interior. By studying the gases that are released from inside Earth, we can learn more about the original sources of volatile elements. Different volatile origins will have different chemical signatures – akin to a fingerprint. Some of these chemical signatures may have been preserved deep within Earth's mantle for most of Earth’s history. In this research project, researchers will use new analytical techniques to study the composition of gases from Earth's mantle, focusing on samples from magmatic carbon dioxide (CO2) wells in Australia and the Colorado Plateau. This team also hopes to gain insight into how carbon dioxide can be stored underground, which could help us combat increasing levels of CO2 in the atmosphere and climate change. The natural movement of CO2 gas through Earth's subsurface can provide clues about how we can store CO2 effectively over long periods of time. In the Australian field site, magmatic CO2 gas is being re-injected into the ground to study whether long term geological storage is a viable tool to tackling rising atmospheric CO2 levels. This project will also provide opportunities for undergraduate students to gain experience in various aspects of scientific research such as fieldwork, laboratory work, modeling, and data analysis. Past measurements of noble gases in CO2 well gases in the Colorado Plateau provide important constraints on the cycling of volatiles within Earth’s mantle. Owing to their chemical and biological inertness, noble gases are exceptionally conservative tracers of sources and processes. New high-precision measurements of Ar, Kr, and Xe isotopes in CO2 well gas samples – made at 10 to 100 times higher precision than was previously attainable – will shed new light on the timing of volatile cycling and the cosmochemical origin of heavy noble gases in our atmosphere. Novel state-of-the-art measurements of clumped N2 and CH4 in these systems will provide unprecedented insight into the formation temperature and sources of volatiles, which will aid in understanding the recycling of deep nitrogen to the atmosphere and in disentangling biotic from abiotic methane production in hydrothermal systems. In cooperation with colleagues working on CO2 sequestration projects in Australia, measurements of noble gas isotopes made before, and after, test injection will be utilized as a novel tracer for subsurface transport of injected CO2, with possible implications for monitoring other sequestration sites worldwide. The new measurements made in this study will be shared with the broader community through a series of peer-reviewed publications, conference presentations, and will be made freely available to the public through online data repositories. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.