@article{fdi:010053080,
  title = {{P}etrological analysis of the pre-eruptive magmatic process prior to the 2006 explosive eruptions at {T}ungurahua volcano ({E}cuador)},
  author = {{S}amaniego, {P}ablo and {L}e {P}ennec, {J}ean-{L}uc and {R}obin, {C}laude and {H}idalgo, {S}.},
  editor = {},
  language = {{ENG}},
  abstract = {{U}nderstanding the processes at the origin of explosive events is crucial for volcanic hazard mitigation, especially during long-lasting eruptions at andesitic volcanoes. {T}his work exposes the case of {T}ungurahua volcano, whose unrest occurred in 1999. {S}ince this date, the eruptive activity was characterized by low-to moderate explosiveness, including phases with stronger canon-like explosions and regional ash fallout. {H}owever, in 2006, a sudden increase of the explosiveness led to pyroclastic flow-forming eruptions on {J}uly 14th ({VEI} 2) and {A}ugust 16-17th ({VEI} 3). {A}ll magmas emitted from 1999 to 2005, as well as the samples from the 2006 eruptions, have homogeneous bulk-rock andesitic compositions (58-59 wt.% {S}i{O}2), and contain the same mineral assemblage consisting of pl + cpx + opx + mag +/- ol. {H}owever, during the {A}ugust 16-17th event, the erupted tephra comprise two types of magmas: a dominant, brown andesitic scoria; and scarce, light-grey pumice representing a subordinate, silica-rich juvenile component. {F}or the andesitic magma, thermobarometric data point to magmatic temperatures ranging from 950 to 1015 degrees {C} and pressures in the range of 200 to 250 {MP}a, which corresponds to 7.5-9.5 km below the summit. {D}isequilibrium textures in plagioclase and pyroxene phenocrysts, particularly thin overgrowth rims, indicate the recharge of this magma body by mafic magma. {B}etween 1999 and 2005, repeated injections from depth fed the intermittent eruptive activity observed while silica-rich melts were produced by in-situ crystallization in the peripheral parts of the reservoir. {I}n {A}pril 2006, the recharge of a primitive magma produced strong convection and homogenisation in the reservoir, as well as pressure increase and higher magma ascent rate after seven years of only moderately explosive activity. {T}his work emphasizes the importance of petrological studies in constraining the pre-eruptive magmatic conditions and processes, as a tool for understanding the fundamental causes of the changes in the eruptive dynamism, particularly the occurrence of paroxysmal phases in andesitic systems with open-vent behaviour.},
  keywords = {{T}ungurahua ; {E}cuador ; magma mixing ; recharge ; thermobarometry ; plumbing ; system},
  booktitle = {},
  journal = {{J}ournal of {V}olcanology and {G}eothermal {R}esearch},
  volume = {199},
  numero = {1-2},
  pages = {69--84},
  ISSN = {0377-0273},
  year = {2011},
  DOI = {10.1016/j.jvolgeores.2010.10.010},
  URL = {https://www.documentation.ird.fr/hor/fdi:010053080},
}