The Magmatic Gas Signature of Pacaya Volcano, With Implications for the Volcanic CO₂ Flux From Guatemala

Abstract

Pacaya volcano in Guatemala is one of the most active volcanoes of the Central American Volcanic Arc (CAVA). However, its magmatic gas signature and volatile output have received little attention to date. Here, we present novel volcanic gas information from in‐situ (Multi‐GAS) and remote (UV camera) plume observations in January 2016. We find in‐plume H2O/SO2 and CO2/SO2 ratios of 2‐20 and 0.6‐10.5, and an end‐member magmatic gas signature of 80.5 mol. % H2O, 10.4 mol. % CO2, and 9.0 mol. % SO2. The SO2 flux is evaluated at 885 ± 550 tons/d. This, combined with co‐acquired volcanic plume composition, leads to H2O and CO2 fluxes of 2,230 ± 1,390 and 700 ± 440, and a total volatile flux of ∼3,800 tons/d. We use these results in tandem with previous SO2 flux budgets for Fuego and Santiaguito to estimate the total volcanic CO2 flux from Guatemala at ∼1,160 ± 600 tons/day. This calculation is based upon CO2/total S (St) ratios for Fuego (1.5 ± 0.75) and Santiaguito (1.4 ± 0.75) inferred from a gas (CO2/St ratio) versus trace‐element (Ba/La ratio) CAVA relationship. The H2O‐poor and low CO2/St ratio (∼1.0‐1.5) signature of Pacaya gas suggests dominant mantle‐wedge derivation of the emitted volatiles. This is consistent with 3He/4He ratios in olivine hosted fluid inclusions (FIs), which range between 8.4 and 9.0 Ra (being Ra the atmospheric 3He/4He ratio) at the upper limit of MORB range (8 ± 1 Ra). These values are the highest ever measured in CAVA and among the highest ever recorded in arc volcanoes worldwide, indicating negligible 4He contributions from the crust/slab.

Geochemistry of Noble Gases and CO2 in Fluid Inclusions From Lithospheric Mantle Beneath Wilcza Góra (Lower Silesia, Southwest Poland)

“…As is the case in subduction-related settings (i.e., arc volcanoes), Ne-and Ar-isotope ratios are systematically lower and close to theoretical values in the atmosphere (Hilton et al, 2002;Martelli et al, 2014;Di Piazza et al, 2015;Rizzo et al, 2015;Robidoux et al, 2017;Battaglia et al, 2018), irrespective of whether Ol phenocrysts or mantle xenocrysts are analyzed.…”

Periodicity in Volcanic Gas Plumes: A Review and Analysis

“…The CWT (Figure 4c) also highlights stable periods of 200-300 s and 125-175 s. It is plausible that these periodic components are related to the rheological stiffening of the upper conduit, which was posited by Nadeau et al [80] as a cause of the link between seismicity and gas release. Similarly, reanalysis of timeseries data from Gorely [81] and Pacaya, Guatemala [86] revealed a range of periodicities. At Gorely, a dominant period was discovered at 63 s, with others at 197 and 509 s in Lomb-Scargle analysis (Figure 5b (Figure 5c) shows that some of these are present for a large proportion of the dataset (900-1400 s and 1500-2500 s) but that spikes between 200-700 s were more transient and likely related to the mild strombolian activity during acquisition [86].…”

“…Similarly, reanalysis of timeseries data from Gorely [81] and Pacaya, Guatemala [86] revealed a range of periodicities. At Gorely, a dominant period was discovered at 63 s, with others at 197 and 509 s in Lomb-Scargle analysis (Figure 5b (Figure 5c) shows that some of these are present for a large proportion of the dataset (900-1400 s and 1500-2500 s) but that spikes between 200-700 s were more transient and likely related to the mild strombolian activity during acquisition [86].…”

AGU Centennial Grand Challenge: Volcanoes and Deep Carbon Global CO2 Emissions From Subaerial Volcanism—Recent Progress and Future Challenges

“…The DECADE initiative has funded installation of a gas (Multi‐GAS; Aiuppa et al, ; Shinohara, ) monitoring network that covers some (>10) of the world's 90 top degassing volcanoes, allowing for volcanic CO 2 observations of much improved continuity and temporal resolution, with obvious benefits for volcano monitoring (Aiuppa et al, ; Aiuppa, Bitetto, et al, ; de Moor, Aiuppa, Avard, et al, ; de Moor, Aiuppa, Pacheco, et al, ; de Moor et al, ). DECADE, in combination with other international research initiatives (e.g., http://www.trailbyfire.org), has also funded campaign‐style surveys and/or temporary Multi‐GAS deployments at many strongly degassing volcanoes whose CO 2 flux was previously unknown (e.g., Aiuppa et al, ; Tamburello et al, , ; Bani, Rose‐Koga, et al, , Bani, Alfianti, et al, ; Battaglia et al, ; de Moor et al, ; Moussallam et al, ).…”