New Seafloor Sampling Methods for Noble Gases: A Trial at Loihi Seamount

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Intellectual Merit: This research evaluates the importance of atmospheric contamination of seafloor volcanic glasses during sample collection and processing (both on the ship and in the laboratory). Samples will be collected from Loihi Seamount, Hawaii using a novel, newly developed, air-tight sampler that eliminates exposure to air. Submarine glasses provide important archives of mantle noble gases which are key indicators of mantle degassing and circulation. Unfortunately, the characterization of the heavy noble gases, particularly the isotopes of argon and xenon in submarine glasses has been hampered by atmospheric contamination. At present the mechanism of contamination is unknown. This research tests the hypothesis that most air contamination is introduced during sample processing and storage and that it can be avoided by a new sampling protocol involving air-free handling. The project involves collecting volcanic glasses from rocks on the seafloor using a pressurized vessel and subsequently transferring samples to a pure nitrogen atmosphere and then into special vacuum containers for analysis. Noble gases will then be measured by mass spectrometry after crushing and/or melting in the laboratory. Analytical results will be compared to splits of the same samples collected using conventional methods, i.e. exposed to air. Experiments will also examine whether contamination is related to glass vesicularity. Broader Impacts: The primary broader impact will be the development of new air-free sampling and analytical protocols for seafloor volcanic glasses containing noble gases. The newly designed sampler may have possible application to other fields that require air-tight sampling at high pressures, such as microbiology. Work involves bi-coastal institutional collaboration and will support graduate student and undergraduate training. A website allowing public access to research results will be created at the Woods Hole Oceanographic Institution.