## 6 Conclusions  
Global inventories of volcanic gas data remain sparse and incomplete, especially for remotely located volcanic centers such as Mount Garet, in Gaua. Less than 60 of the several hundred currently degassing Holocene volcanoes have been characterized geochemically for their gas emissions and less than a few (\(<\)10) volcanoes have permanent in-situ instrumentation operating in real-time. In this study we presented volcanic gas composition data from Mount Garet volcano. Our survey provides the first characterization of plume chemistry for this volcano. Although results reported here are punctual, they set unprecedented information on the composition and flux of volcanic gases at Mount Garet during a quiescent activity period (December 2018). By combining our results with satellite-based SO\({}_{2}\) flux measurements (average of 434 t d\({}^{-1}\) over the 2005-2015 period) we estimated H\({}_{2}\)O, CO\({}_{2}\), H\({}_{2}\)S, and H\({}_{2}\) outputs of \(\sim\)5758 t d\({}^{-1}\), \(\sim\)259 t d\({}^{-1}\), \(\sim\)30 t d\({}^{-1}\), and \(\sim\)0.5 t d\({}^{-1}\). These results rank Mount Garet as an intermediate-size volcanic CO\({}_{2}\) point source, well below the intense CO\({}_{2}\) emissions derived for nearby Ambrym (until its 2018 eruption) and Yasur volcanoes further south in the same Vanuatu arc. We caution that our observations are only likely to be reprehensive of Mt. Garet's quiescent emissions, while much higher CO\({}_{2}\) and total volatile fluxes are likely to be associated with eruptive phases, as for instance supported by the high SO\({}_{2}\) flux emissions measured during the 2009-2010 period of unrest (for which no gas composition is unfortunately available). Our results thus confirm the need to better constrain the temporal variability of gas compositions through periodic and/or continuous surveys. Resolving the volatile output for both quiescent and unrest phases, along with newly reported volcanic gas plume compositions, would foster the ability to interpret volcanic gas monitoring signals and perform hazard assessments in the future. Our volcanic gas survey has also revealed an especially C-poor composition (CO\({}_{2}\)/ST \(\sim\)0.9) for Mount Garet volcano, well below the compositions derived for nearby Ambrym and Yasur (CO\({}_{2}\)/ST \(\sim\)1.5 to 1.6), and un-matching with the previously predicted volcanic gas compositions for the same volcano (CO\({}_{2}\)/ST \(\sim\)2.5). The contrast between the relatively high C content of sediments at the Vanuatu trench and the CO\({}_{2}\)-poor nature of volcanic gases measured at Mount Garet during our 2018 field campaign is intriguing. In other volcanic arcs where C is subducted through sediments (northern segments of the Andean Volcanic Belt, for example), volcanic gases typically display higher CO\({}_{2}\)/ST ratios (\(\sim\)2-4). Furthermore, despite the fact that recent gas studies at other persistently degassing Melanesian volcanoes have reported similar in-plume volatile signatures, more volcanic gas surveys are needed to accurately assess the apparent mismatch between the high C input (sediments) and the low C output (volcanic gases). That will ultimately allow for more robust arc-scale interpretations of the nature of gas emissions from Southwest Pacific volcanism, a region of much relevance to arc CO\({}_{2}\) budgets globally, and their implications for our overall understanding of global geochemical cycles and atmospheric evolution over time. The following are available online at [[http://www.mdpi.com/2076-3417/10/20/7293/s1](http://www.mdpi.com/2076-3417/10/20/7293/s1)]([http://www.mdpi.com/2076-3417/10/20/7293/s1](http://www.mdpi.com/2076-3417/10/20/7293/s1)), Supplementary Material S1: \"specifications on multi-GAS infrared (IR) and electrochemical sensors and gas standards used for instrument calibration\" is available for consultation. Conceptualization, J.L., Y.M., P.B. and N.P. ; project administration, Y.M. ; data acquisition, J.L., Y.M., P.B. and N.P. ; data curation, J.L. ; graphical editing, J.L.