@article{PAR00002187,
  title = {{S}tructural and metamorphic evolution of the {A}mbin massif (western {A}lps) : toward a new alternative exhumation model for the {B}rianconnais domain},
  author = {{G}anne, {J}{\'e}r{\^o}me and {B}ertrand, {J}. {M}. and {F}udral, {S}. and {M}arquer, {D}. and {V}idal, {O}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he basement domes of the central part of western {A}lps may result either from a multistage tectonic evolution with a dominant horizontal shortening component, an extensional behaviour, or both. {T}he {A}mbin massif belongs to the "{B}rianconnais" domain and is located within the {HP} metamorphic zone. {I}t was chosen for a reappraisal of the tectonic evolution of the {I}nternal {A}lps in its western segment. {S}tructural investigations have shown that {A}lpine {HP} rocks were exhumed in three successive stages. {T}he {D}1 stage was roughly coeval with the observed peak metamorphic conditions and corresponds to a non-coaxial regime with dominant horizontal shortening and north movement direction. {P}etrological observations and {P}-{T} estimates show that the exhumation process was initiated during {D} {I}, the corresponding mechanism being still poorly understood. {T}he {D}2 stage took place under low-blueschist facies conditions and culminated under greenschist facies conditions. {I}t developed a retrogressive foliation and pervasive shear-zones at all scales that locally define major tectonic contacts. {D}2 shear zones show a top-to-east movement direction and correspond actually to large-scale detachment faults responsible for the juxtaposition of less metamorphic units above the {A}mbin basement and thus to a large part of the exhumation of {HP} rocks toward the surface. {D}2 shear zones were {S}ubsequently deformed by {D}3 open folds, large antiforms (e.g. the {A}mbin dome) and associated brittle-ductile {D}3 shear-bands. {T}he {D}1 to {D}3 {P}-{T} conditions and {P}-{T} path of the blueschists {O}ccurring in the deepest part of the {A}mbin dome, was estimated by using the multi-equilibrium thermobarometric method of the {T}weeq and {T}hermocalc softwares. {P}eak pressure conditions, estimated at about 14-16 {K}b, 500 degrees {C}, are followed by a nearly-isothermal decompression that occurred concurrently with the major {D}1-{D}2 change in the ductile deformation regime. {E}astwards, the {S}chistes {L}ustres units exhibit a similar geometry on top of the {G}ran {P}aradiso dome but exhibit opposite {D}2 movement direction. {L}ower-grade units are lying above higher-grade units, the shear zones occurring in between being similar to {A}mbin's {D}2 detachments. {T}hus at regional scale, the {D}2 detachments seem to form together with the {A}mbin shear-zones, a network of conjugate detach men {I}s. {S}uch a pattern suggests that the exhumation history is mostly controlled by a {D}2+{D}3 crustal-scale vertical shortening resulting in the thinning of the previous tectonic pile formed during {D}1. {T}he slab-break off hypothesis may explain {S}uch an extensional behaviour within the western {P}ennine domain, {I}t is {S}uggested that the thermo-mechanical rebound of the residual {E}uropean slab initiated between 35 and 32 {M}a the fast exhumation of the previously thickened orogenic wedge (stack of {D} {I} {HP} slices). {I}t was immediately followed by a collapse of the wedge that may correspond to the {E}-{W} {O}ligocene extensional event responsible for the opening of rifts in the {W}est {E}uropean platform.},
  keywords = {},
  booktitle = {},
  journal = {{B}ulletin de la {S}ociete {G}eologique de {F}rance},
  volume = {178},
  numero = {6},
  pages = {437--458},
  ISSN = {0037-9409},
  year = {2007},
  DOI = {10.2113/gssgfbull.178.6.437},
  URL = {https://www.documentation.ird.fr/hor/{PAR}00002187},
}