First airborne samples of a volcanic plume for δ13C of CO2 determinations

Volcanic degassing is one of the main natural sources of CO2 to the atmosphere. Carbon isotopes of volcanic gases enable the determination of CO2 sources including mantle, organic or carbonate sediments, and atmosphere. Until recently, this work required sample collection from vents followed by laboratory analyses. Isotope ratio infrared analyzers now enable rapid analyses of plume delta C-13-CO2, in situ and in real time. Here we report the first analyses of delta C-13-CO2 from airborne samples. These data combined with plume samples from the vent area enable extrapolation to the volcanic source delta C-13. We performed our experiment at the previously unsampled and remote Kanaga Volcano in the Western Aleutians. We find a delta C-13 source composition of -4.4 parts per thousand, suggesting that CO2 from Kanaga is primarily sourced from the upper mantle with minimal contributions from subducted components. Our method is widely applicable to volcanoes where remote location or activity level precludes sampling using traditional methods.