@article{fdi:010054192,
  title = {{H}ydrothermal alteration in andesitic volcanoes : trace element redistribution in active and ancient hydrothermal systems of {G}uadeloupe ({L}esser {A}ntilles)},
  author = {{S}alaun, {A}. and {V}illemant, {B}. and {G}{\'e}rard, {M}artine and {K}omorowski, {J}. {C}. and {M}ichel, {A}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he mineralogy and the trace element compositions of hydrothermally-altered volcanic materials collected from ash fall deposits and in four debris-avalanche deposits ({DAD}s) at {L}a {S}oufriere volcano in {G}uadeloupe have been determined. {P}hreatic explosions of the 1976 eruption and flank collapse events have sampled various parts of the active and ancient hydrothermal systems of the volcano. {H}ydrothermal mineral assemblages (smectite + silica polymorphs +/- pyrite/jarosite +/- gypsum) are typical of rock alteration by low-temperature acid-sulphate fluids. {H}igh-temperature mineral assemblages are rare, indicating that phreatic explosions and flank collapse events have sampled mainly the upper parts of the volcanic edifice. {A}ndesitic eruptive products affected by shallow hydrothermal alteration are complex assemblages of volcanic materials (glass, phenocrysts and xenocrysts with complex magmatic histories) of different ages and compositions. {T}he use of incompatible element ratios and {REE} compositions normalised to an unaltered reference material overcomes the interpretation difficulties related to mass balance effects of alteration processes and the petrologic heterogeneity of the initial material. {REE} and other incompatible elements ({T}h, {U}, {H}f, {Z}r) are mainly concentrated in the glassy matrix of unaltered andesitic rocks. {S}econdary {S}-bearing mineral phases (e.g., gypsum, jarosite) that have precipitated from acid-sulphate fluids do not contain substantial incompatible elements ({REE}, {U}. {T}h, {H}f, {Z}r). {C}ompositional variations of incompatible elements in hydrothermally-altered andesitic materials reflect mainly volcanic glass-smectite transformation, which is characterised by (i) strong depletion of alkalis and alkaline earths ({B}a, {S}r) and first transition series elements ({Z}n, {C}u, {C}r, {C}o, {N}i), (ii) immobility of highly incompatible elements ({T}h, {Z}r, {H}f, {LREE}) and (iii) strong depletion of {MREE} and {HREE}. {T}he sigmoid shape of normalised {REE} pattern is characteristic of glass-smectite transformation by low-temperature acid-sulphate fluids. {T}his transformation also produces significant variations in {U}/{T}h values, which offer the opportunity to date the cessation of hydrothermal alteration and to reconstruct the evolution in space and time of hydrothermal activity in a volcanic edifice.},
  keywords = {{H}ydrothermal alteration ; {T}race elements ; {REE} ; {U} ; {A}ndesites ; {F}lank ; collapse},
  booktitle = {},
  journal = {{J}ournal of {G}eochemical {E}xploration},
  volume = {111},
  numero = {3},
  pages = {59--83},
  ISSN = {0375-6742},
  year = {2011},
  DOI = {10.1016/j.gexplo.2011.06.004},
  URL = {https://www.documentation.ird.fr/hor/fdi:010054192},
}