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Trace volatile elements like He are key for understanding the mantle source signature of magmas and to better constrain the relative roles of subduction and crustal processes to the variability of along-arc chemical and isotopic signatures of magmatic fluids. Here we report on noble gas abundances and isotopic data of Fluid Inclusions (FIs) in eruptive products and/or fumarolic gases from the Colombia-Ecuador segment of Andean Northern Volcanic Zone (NVZ). FIs in olivine phenocrysts from Ecuador (El Reventador, Cotopaxi and Tungurahua) yield air-normalized corrected He-3/He-4 ratios of 7.0-7.4 R-A, within the MORB range (8 +/- 1 R-A). With exception of the Cotopaxi lavas (opx < < oliv.), these are indistinguishable of those obtained for their cogenetic orthopyroxene pairs and of gas emissions previously reported in literature. Olivine phenocrysts from Nevado del Ruiz fissure lavas also yield the highest He-3/He-4 (8.5 +/- 0.3 R-A) for this volcanic system, which is in the range of fumarolic gases for Galeras (previously reported as high as 8.8 R-A and here measured to a maximum of 8.3 +/- 0.1 R-A). Our dataset highlights disparities between isotope signatures of eruptive products from Ecuador (avg. similar to 7.2 R-A) and those reported for the Colombian portion of the NVZ (avg. similar to 8.5 R-A). Previous studies on the geochemistry of erupted products put in evidence significant along-arc variations ascribed either to the involvement of different slab components, or to variable depths of evolution of arc magmas within the continental crust. However, the same variation is not discernible in the signature of noble gases, especially helium, from FIs and gas emissions analyzed in this study, with little inter-variation between Cotopaxi, Reventador and Tungurahua (all within 0.2 R-A from the Ecuador average of 7.2) and Galeras and Nevado del Ruiz, whose maximum values differ by similar to 0.3 RA. We therefore suggest a homogenous MORB-like He-3/He-4 signature for the mantle wedge beneath this arc segment, whereby along-arc variations in crustal thickness (from = 50 km at the Ecuadorian arc segment) may factor largely into the variability recorded on our data set. The first CO2/He-3 ratios obtained in FIs from Andean rocks support the hypothesis of increasing crustal contamination from Colombia to Ecuador, concomitant with increasing crustal thicknesses under the respective arc regions.

Recent volcanic gas compilations have urged the need to expand in-situ plume measurements to poorly studied, remote volcanic regions. Despite being recognized as one of the main volcanic epicenters on the planet, the Vanuatu arc remains poorly characterized for its subaerial emissions and their chemical imprints. Here, we report on the first plume chemistry data for Mount Garet, on the island of Gaua, one of the few persistent volatile emitters along the Vanuatu arc. Data were collected with a multi-component gas analyzer system (multi-GAS) during a field campaign in December 2018. The average volcanic gas chemistry is characterized by mean molar CO2/SO2, H2O/SO2, H2S/SO2 and H2/SO2 ratios of 0.87, 47.2, 0.13 and 0.01, respectively. Molar proportions in the gas plume are estimated at 95.9 &plusmn, 11.6, 1.8 &plusmn, 0.5, 2.0 &plusmn, 0.01, 0.26 &plusmn, 0.02 and 0.06 &plusmn, 0.01, for H2O, CO2, SO2, H2S and H2. Using the satellite-based 10-year (2005&ndash, 2015) averaged SO2 flux of ~434 t d&minus, 1 for Mt. Garet, we estimate a total volatile output of about 6482 t d&minus, 1 (CO2 ~259 t d&minus, 1, H2O ~5758 t d&minus, H2S ~30 t d&minus, H2 ~0.5 t d&minus, 1). This may be representative of a quiescent, yet persistent degassing period at Mt. Garet, whilst, as indicated by SO2 flux reports for the 2009&ndash, 2010 unrest, emissions can be much higher during eruptive episodes. Our estimated emission rates and gas composition for Mount Garet provide insightful information on volcanic gas signatures in the northernmost part of the Vanuatu Arc Segment. The apparent CO2-poor signature of high-temperature plume degassing at Mount Garet raises questions on the nature of sediments being subducted in this region of the arc and the possible role of the slab as the source of subaerial CO2. In order to better address the dynamics of along-arc volatile recycling, more volcanic gas surveys are needed focusing on northern Vanuatu volcanoes.

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/S-T ratio of 3.9 +/- 1.6 (S-T is total sulfur, S). Contemporary, fumarolic chemistry at Galeras progressively shifted toward low-temperature, S-depleted fumarolic gas discharges with an average CO2/S-T 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 similar to 2.5 kg/s (similar to 213 t/day). For comparison, SO2 emissions remained high at Nevado del Ruiz (weighted average of 8 kg/s) between 2014 and 2017, while Purace maintained rather low emission levels (