@article{fdi:010080548, title = {{F}irst gas and thermal measurements at the frequently erupting {G}amalama volcano ({I}ndonesia) reveal a hydrothermally dominated magmatic system}, author = {{K}unrat, {S}. and {B}ani, {P}hilipson and {H}aerani, {N}. and {S}aing, {U}. {B}. and {A}iuppa, {A}. and {S}yahbana, {D}. {K}.}, editor = {}, language = {{ENG}}, abstract = {{T}he first gas and thermal measurements at the summit of the {G}amalama volcano indicate that the system is dominated by hydrothermal processes. {T}his is highlighted by the prevalence of {H}2{S} over {SO}2 ({H}2{S}/{SO}2 = 2-8), a high {CO}2/{SO}2 ratio (76-201), and a low heat transfer (3.0 {MW}) to the surface. {A} relative variation in gas composition is observed along the degassing fracture zone, possibly due to partial {S} scrubbing. {D}espite this surface hydrothermal signature, the system exhibits high gas equilibrium temperatures (425-480 degrees {C}), indicating that fluids are not exclusively derived from a boiling hydrothermal aquifer, but also sourced by cooling and crystallizing basaltic magma at deep that continues to inject magmatic fluids into the system. {T}his hydrothermally dominated activity on {G}amalama possibly persisted over the last two decades, during which a high number of eruptive events were witnessed. {T}he period coincides with the opening of large fractures at the summit that subsequently shifted the volcanic activity from the crater center to the peripheral fractures zones. {T}hese fractures that possibly developed in response to the regional geodynamics, have weakened the hydrothermal seal, allowing the pressure developed by the hydrothermal-magmatic system and promoted by the high annual rainfall, to rapidly exceeds the tensile strength of the seal leading to the numerous phreatic eruptions.}, keywords = {{G}amalama volcano ; {D}ominated hydrothermal system ; {P}ressure and tensile strength ; {INDONESIE} ; {GAMALAMA} {VOLCAN}}, booktitle = {}, journal = {{J}ournal of {V}olcanology and {G}eothermal {R}esearch}, volume = {407}, numero = {}, pages = {107096 [11 ]}, ISSN = {0377-0273}, year = {2020}, DOI = {10.1016/j.jvolgeores.2020.107096}, URL = {https://www.documentation.ird.fr/hor/fdi:010080548}, }