@article{fdi:010073699,
  title = {{S}tructure of the acid hydrothermal system of {P}apandayan volcano, {I}ndonesia, investigated by geophysical methods},
  author = {{B}yrdina, {S}vetlana and {G}randis, {H}. and {S}umintadireja, {P}. and {C}audron, {C}. and {S}yahbana, {D}. {K}. and {N}affrechoux, {E}. and {G}unawan, {H}. and {S}uantika, {G}. and {V}andemeulebrouck, {J}.},
  editor = {},
  language = {{ENG}},
  abstract = {{P}apandayan (2665 m asl) is an {I}ndonesian stratovolcano located at 50 km from {B}andung in west {J}ava and characterized by an intense hydrothermal activity. {A}n advanced alteration takes place where acid fluids interact with rocks, weakening the edifice, so that even minor explosive eruptions threaten the stability of its flanks. {T}he purpose of the current study is to delineate the geometry of the acid hydrothermal plume using {E}lectrical {R}esistivity {T}omography ({ERT}). {W}e used self-potential, p{H} measurements in water (in situ) and of soil samples, {SO}2 and {CO}2 soil concentration mappings to better understand the resistivity structure. {M}easurements have been performed inside the 1772 crater with a maximal depth of investigation of about 250 m for electrical resistivity tomography. {A}t low p{H}, the mobility of {H}+ (or {H}3{O}+) ions represents a dominant contribution to the electrical conductivity leading to an unusually high conductivity of pore water. {F}or {P}apandayan spring water, the theoretical electrical conductivity calculated for chemical composition and p{H} yield indeed exceptionally high values in the range 20- 25{S}m(-1). {T}he surface conductivity of the altered unconsolidated samples determined from a recent study (< 0.04{S}m(-1)) is negligible in comparison with the conductivity of the pore water. {T}he theoretical conductivity values are then compared with the results of our geophysical survey. {O}ur 3-{D} inversion of electrical resistivity data identifies the entire crater of {P}apandayan volcano as a relatively conductive medium (>0.005{S}m-1) with an extremely high bulk conductivity within the central part of the crater (similar to 2{S}m(-1)). {T}he main degassing zones in the crater, {K}awah {E}mas, {M}anuk and {K}awah {B}aru, are all connected by conduits to this common reservoir at a depth of 100 m. {B}ecause the location of this good conductor coincides with elevated ground temperature, main fumaroles, and with detectable {SO}2 degassing, we interpret it as an acid hydrothermal plume. {L}ow p{H} impacts also the self-potential distribution: a clear correlation is observed between the p{H} values measured in soil samples and the self-potential. {T}he main degassing area is associated with a negative anomaly of self-potential likely produced by the electro-kinetic effect due to upwelling fluid flow in acid conditions. {I}t follows from our results that the assessment of the p{H} conditions is necessary for the interpretation of electrical resistivity structures and self-potential distribution on hydrothermal systems where acid conditions and acidity variations can be expected due to chemical reactions between volcanic gases and groundwater.},
  keywords = {{H}ydrothermal system ; {ERT} ; {A}cid-sulfate ; p{H} and conductivity ; {P}apandayan ; {INDONESIE} ; {PAPANDAYAN} {VOLCAN}},
  booktitle = {},
  journal = {{J}ournal of {V}olcanology and {G}eothermal {R}esearch},
  volume = {358},
  numero = {},
  pages = {77--86},
  ISSN = {0377-0273},
  year = {2018},
  DOI = {10.1016/j.jvolgeores.2018.06.008},
  URL = {https://www.documentation.ird.fr/hor/fdi:010073699},
}