@article{fdi:010068352, title = {{P}rodigious emission rates and magma degassing budget of major, trace and radioactive volatile species from {A}mbrym basaltic volcano, {V}anuatu island {A}rc}, author = {{A}llard, {P}. and {A}iuppa, {A}. and {B}ani, {P}hilipson and {M}etrich, {N}. and {B}ertagnini, {A}. and {G}authier, {P}. {J}. and {S}hinohara, {H}. and {S}awyer, {G}. and {P}arello, {F}. and {B}agnato, {E}. and {P}elletier, {B}ernard and {G}araebiti, {E}.}, editor = {}, language = {{ENG}}, abstract = {{A}mbrym volcano, in the {V}anuatu arc, is one of the most active volcanoes of the {S}outhwest {P}acific region, where persistent lava lake and/or {S}trombolian activity sustains voluminous gas plume emissions. {H}ere we report on the first comprehensive budget for the discharge of major, minor, trace and radioactive volatile species from {A}mbrym volcano, as well as the first data for volatiles dissolved in its basaltic magma (olivine-hosted melt inclusions). {I}n situ {M}ulti{GAS} analysis of {H}2{O}, {CO}2, {SO}2 and {H}2{S} in crater rim emissions, coupled with filter-pack determination of {SO}2, halogens, stable and radioactive metals demonstrates a common magmatic source for volcanic gases emitted by its two main active craters, {B}enbow and {M}arum. {T}hese share a high water content (similar to 93 mol%), similar {S}/{C}l, {C}l/ {F}, {B}r/{C}l molar ratios, similar ({P}o-210/{P}b-210) and ({B}i-210/(210{P})b) activity ratios, as well as comparable proportions in most trace metals. {T}heir difference in {CO}2/{SO}2 ratio (1.0 and 5.6-3.0, respectively) is attributed to deeper gas melt separation at {M}arum ({S}trombolian explosions) than {B}enbow (lava lake degassing) during our measurements in 2007. {A}irborne {UV} sensing of the {SO}2 plume flux (90 kg s(-1) or 7800 tons d(-1)) demonstrates a prevalent degassing contribution (similar to 65%) of {B}enbow crater in that period and allows us to quantify the total volatile fluxes during medium-level eruptive activity of the volcano. {R}esults reveal that {A}mbrym ranks among the most powerful volcanic gas emitters on {E}arth, producing between 5% and 9% of current estimates for global subaerial volcanic emissions of {H}2{O}, {CO}2, {HC}l, {C}u, {C}r, {C}d, {A}u, {C}s and {T}l, between 10% and 17% of {SO}2, {HF}, {HB}r, {H}g, {P}o-210 and {P}b-210, and over 30% of {A}g, {S}e and {S}n. {G}lobal flux estimates thus need to integrate its contribution and be revised accordingly. {P}rodigious gas emission from {A}mbrym does not result from an anomalous volatile enrichment nor a differential excess degassing of its feeding basalt: this latter contains relatively modest dissolved amounts of {H}2{O}(<= 1.3 wt%), {CO}2 (similar to 0.10 wt%), {S} (0.075 wt%) and {C}l (0.05 wt%), and its degassing under prevalent closed-system conditions well reproduces the composition of emitted volcanic gases. {I}nstead, we show that the gas discharge is sustained by a very high basalt supply rate of 25 m(3) s(-1), from a large (similar to 0.5 km(3)) magma reservoir probably emplaced at similar to 3.8 km depth below the summit caldera according to both the {H}2{O}-{CO}2 content of bubble-free melt inclusions and preliminary seismic data. {R}adioactive disequilibria in the volcanic gases constrain that this reservoir may be entirely renewed in about 240 days. {T}he comparatively low magma extrusion rate requires extensive convective overturn of the basaltic magma column and recycling of the unerupted (denser) degassed magma in the plumbing system, in agreement with textural features of erupted products. {F}inally, our results suggest that the {I}ndian {MORB}-type mantle source of {A}mbrym basalts is modestly enriched in slab-derived water and other volatiles, in agreement with the prevalent volcanodastic nature of subducted sediments and their lower subduction rate under the central {V}anuatu arc due to its collision with the {D}'{E}nfrecasteaux {R}idge.}, keywords = {{A}mbrym ; {V}anuatu ; {V}olatile fluxes ; {M}agma degassing budget ; {M}agma reservoir ; {R}adioactive disequilibria ; {PACIFIQUE} {SUD} ; {VANUATU} ; {AMBRYM} {VOLCAN}}, booktitle = {{U}nderstanding volcanoes in the {V}anuatu arc}, journal = {{J}ournal of {V}olcanology and {G}eothermal {R}esearch}, volume = {322}, numero = {{N}o {S}p{\'e}cial}, pages = {119--143}, ISSN = {0377-0273}, year = {2016}, DOI = {10.1016/j.jvolgeores.2015.10.004}, URL = {https://www.documentation.ird.fr/hor/fdi:010068352}, }