Volcanic Gas Emissions Along the Colombian Arc Segment of the Northern Volcanic Zone (CAS‐NVZ): Implications for volcano monitoring and volatile budget of the Andean Volcanic Belt

Studying spatial and temporal trends in volcanic gas compositions and fluxes is crucial both to
volcano monitoring and to constrain the origin and recycling efficiency of volatiles at active convergent
margins. New volcanic gas compositions and volatile fluxes are here reported for Nevado del Ruiz, Galeras,
and Purace, three of the most persistently degassing volcanoes located in the Colombian Arc Segment
of the Northern Volcanic Zone. At Nevado del Ruiz, from 2014 to 2017, plume emissions showed an average
molar CO2/ST ratio of 3.9 ± 1.6 (ST is total sulfur, S). Contemporary, fumarolic chemistry at Galeras
progressively shifted toward low‐temperature, S‐depleted fumarolic gas discharges with an average CO2/ST
ratio in excess of 10 (6.0–46.0, 2014–2017). This shift in volcanic gas compositions was accompanied by a
concurrent decrease in SO2 emissions, confirmed on 21 March 2017 by high‐resolution ultraviolet
camera‐based SO2 fluxes of ~2.5 kg/s (~213 t/day). For comparison, SO2 emissions remained high at Nevado
del Ruiz (weighted average of 8 kg/s) between 2014 and 2017, while Puracé maintained rather low emission
levels (<1 kg/s of SO2, CO2/SO2 ≈ 14). We here estimate carbon dioxide fluxes for Nevado del Ruiz,
Galeras, and Puracé of ~23, 30, and 1 kg/s, respectively. These, combined with recent CO2 flux estimates for
Nevado del Huila of ~10 kg/s (~860 t/day), imply that this arc segment contributes about 50% to the total
subaerial CO2 budget of the Andean Volcanic Belt. Furthermore, our work highlights the northward
increase in carbon‐rich sediment input into the mantle wedge via slab fluids and melts that is reflected in
magmatic CO2/ST values far higher than those reported for Southern Volcanic Zone and Central Volcanic
Zone volcanoes. We estimate that about 20% (~1.3 Mt C/year) of the C being subducted (~6.19 Mt C/year)
gets resurfaced through subaerial volcanic gas emissions in Colombia (Nevado del Ruiz ~0.7 Mt C/year). As
global volcanic volatile fluxes continue to be quantified and refined, the contribution from this arc segment
should not be underestimated.