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

Abstract

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.

Noble gas magmatic signature of the Andean Northern Volcanic Zone from fluid inclusions in minerals

“…Ancellin et al (2017Ancellin et al ( , 2019 described similar evidence for the interaction between melts from the subducting Carnegie Ridge (Galapagos Plume track) and the mantle wedge in the northern Andean volcanic zone in Ecuador. A further role of the slab in the region may manifest in a northward increasing input of C-rich fluids from slab sediment decarbonation (Marín-Cerón et al, 2010), which may well explain the higher CO2/ST ratios found in volcanic gases from Galeras and Nevado del Ruiz volcanoes (Aiuppa et al, 2017 andLages et al, 2019;Fig. 4), as well as the higher Ba/La averages in Colombian rocks (e.g., Nevado del Ruiz up to ~62) relative to the Ecuadorian volcanoes here studied (Fig.…”

A Biogeochemical Imprint of the Panama Basin in the North Andean Arc

“…Finally, the anomalously high CO 2 flux observed in Colombian and Ecuadorian volcanoes compared to the rest of the Andean chain (Lages et al., 2019) also suggest a connection with the subduction of the highly productive and carbon‐rich PB. In fact, it has been shown that degassing of the Colombian segment alone contributes to 50% of the total Andean CO 2 emissions (Aiuppa et al., 2017; Lages et al., 2019). The geochemical evidence presented here, together with the extremely high CO 2 fluxes and the recently reported MORB‐like He isotopic signatures of olivine inclusions from the NVP (Lages et al., 2021), not only support the notion of a mantle origin for these typical orogenic andesites, but also make the Northern Andean chain a natural laboratory to test the interconnections among oceans, atmosphere, life, and the solid Earth.…”

“…Finally, the anomalously high CO 2 flux observed in Colombian and Ecuadorian volcanoes compared to the rest of the Andean chain (Lages et al., 2019) also suggest a connection with the subduction of the highly productive and carbon‐rich PB. In fact, it has been shown that degassing of the Colombian segment alone contributes to 50% of the total Andean CO 2 emissions (Aiuppa et al., 2017; Lages et al., 2019).…”

First In-Situ Measurements of Plume Chemistry at Mount Garet Volcano, Island of Gaua (Vanuatu)

“…Multi-GAS data were processed using the Ratiocalc software [47]. We selected specific acquisition time windows showing good temporal correlation (R 2 ≥ 0.70) between volatile concentrations measured simultaneously [48][49][50] (see Figure 3a for different gas species). Molar ratios and errors reported in Table 1 were calculated from the slope and the R 2 value of the best-fit line (linear regression, such as the example of Figure 3b, in black), respectively.…”

“…Aiuppa et al [15,21] noted that this CO 2 -poor volcanic gas composition for the Vanuatu arc, as inferred from observations at Ambrym and Yasur, is somewhat at odds with the relatively high C content of sediment in the subducting slab (bulk sediments in the Vanuatu trench contain up to 4 wt.% CO 2 ) [6]. In other arc sectors where C is subducted via sediments (e.g., Central and northern Southern America) [7], volcanic gases are typically more C-rich, and display characteristics of those volcanoes in the Group 2 category (2 < CO 2 /S T < 4) [15,21,50,58]. In contrast, the Vanuatu gas compositions measured thus far resemble more closely those of subduction zones of the NW Pacific (the Kuril-Kamchatka and Marianas-Japan arc segments) [15], all of which exhibit low C content in subducting sediments [6].…”