CAREER: Heavy Noble Gases in the Azores Archipelago

Washington University, Saint Louis MO

Investigators

Abstract

The terrestrial atmosphere and ocean are unique among Solar System bodies. The heavy noble gases (neon, argon, krypton and xenon) trace where volatiles elements and compounds like carbon, nitrogen and water originated and how their budgets have been distributed between the deep Earth and surface reservoirs over time. Measurements of heavy noble gases in volcanic samples from localities influenced by mantle plumes have yielded new insights into volatile origins and transport, but precise data have come from unusual samples, rather than typical subaerially-erupted ocean island basalts. This integrated research and educational work will harness new technical capabilities to measure heavy noble gases in subaerially-erupted ocean island basalts from the Azores archipelago; this will shed light on how the mantle plume sampled at the Azores acquired and lost volatiles over Earth history and advance the field towards a better understanding of mantle plume volatile signatures. A modern curriculum that presents different isotope systems used to study the geochemistry of the mantle within a uniform framework will be developed and disseminated to broaden the pool of undergraduates who pursue advanced study of the geochemistry of the deep Earth. The heavy noble gases (neon, argon, krypton and xenon) provide unique and powerful insights into volatile accretion, early mantle differentiation, and volatile transport between the interior and surface reservoirs. However, heavy noble gases are difficult to measure in most ocean island basalts due to sample degassing and atmospheric contamination. New analytical techniques have enabled the measurement of heavy noble gas compositions resolved from the atmospheric composition in olivines from ocean islands. This project will sample well-studied sites in the Azores archipelago to obtain large quantities of fresh material for high-precision analysis of helium, neon, argon, krypton and xenon abundances and isotopic ratios. New data will be used to probe mantle volatile origins, test for heterogeneous signatures of volatile loss among mantle plumes, and investigate the efficiency of atmospheric volatile transport into the mantle in the deep past. This project will develop and test a new introductory curriculum for mantle radiogenic isotope geochemistry including noble gases, presented within a unifying framework. Work to disseminate the curriculum to teachers through a workshop and online portals and facilitate its integration into courses will increase and broaden the pool of undergraduates who pursue advanced study of mantle geochemistry, including the noble gases. 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.