@article{fdi:010088412,
  title = {{E}mplacement dynamics of a crystal-rich, highly viscous trachytic flow of the {S}ancy stratovolcano, {F}rance},
  author = {{P}rival, {J}.{M}. and {H}arris, {A}.{J}.{L}. and {Z}anella, {E}. and {R}obustelli {T}est, {C}. and {G}urioli, {L}. and {C}hevrel, {M}agdalena {O}ryaelle and {B}iren, {J}.},
  editor = {},
  language = {{ENG}},
  abstract = {{E}mplacement dynamics of highly viscous, silicic lava flows remain poorly constrained due to a lack of consideration of crystal-rich cases. {E}mplacement models mostly apply to glassy or microlitic, vesiculated rhyolitic flows. {H}owever, crystalline, vesicle-free silicic lava can flow differently. {W}e studied the {G}rande {C}ascade unit, which is a vesicle-free, phenocryst-rich, trachytic flow in the {M}onts {D}ore massif, {F}rance. {F}ield work was carried out to define internal structures, and oriented samples were collected for chemical, petrological, and anisotropy of magnetic susceptibility analyses, allowing us to estimate emplacement temperature and viscosity. {T}hese data allow us to define a new silicic lava flow subtype that is low in temperature (800-900 °{C}), high in silica content (up to 66.8 wt%), high in viscosity (109-1011 {P}a s), rich in phenocrysts (~35%), and lacks vesicles. {B}rittle deformation of the lava occurs upon extrusion, generating a cataclasite basal layer and thin (3-m-thick) shear zone that accommodates all of the stress, allowing most of the flow's volume to slide over its base as a 40-m-thick plug in which there is no deformation. {B}locks are rare, of a single size (10 ± 1 cm), and result from localized break-up of the basal shear zone. {E}mplacement dynamics are different from those of glassy, pumiceous lava flows. {T}hey are closer to glacier dynamics, where most of the volume slides over a thin basal shear zone and till is generated there by abrasion and milling of the underlying layer. {F}or the {G}rande {C}ascade lava flow, abrasion means that the flow lacks its classical blocky crust and instead the flow base is marked by a layer rich in fine-grained material. {T}he structures and emplacement dynamics of this crystal-rich flow are consistent with ideal, gravity-driven shear flow. {W}e thus argue for a global reassessment of silicic-rich lava emplacement based on crystal content and using a multidisciplinary approach focused on well-exposed examples in the rock record.},
  keywords = {{FRANCE} ; {MONT} {DORE} ; {SANCY}},
  booktitle = {},
  journal = {{G}eological {S}ociety of {A}merican {B}ulletin},
  volume = {7-8},
  numero = {},
  pages = {2057--2074},
  ISSN = {0016-7606},
  year = {2023},
  DOI = {10.1130/{B}36415.1},
  URL = {https://www.documentation.ird.fr/hor/fdi:010088412},
}