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TitreThe South Tibetan detachment system facilitates ultra rapid cooling of granulite-facies rocks in Sikkim Himalaya
AuteurKellett, D A; Grujic, D; Coutand, I; Cottle, J; Mukul, M
SourceTectonics vol. 32, issue 2, 2013 p. 252-270, (Accès ouvert)
Séries alt.Secteur des sciences de la Terre, Contribution externe 20120287
Documentpublication en série
Mediapapier; en ligne; numérique
Lat/Long OENS 88.0000 89.5000 28.2500 27.5000
Sujetsdatations radiométriques; datation radiométrique; orogenèse; régions orogéniques; orogénies; déformation; conditions de pression-température; tectonique; géochronologie; géochimie
Illustrationsphotographs; location maps; photomicrographs; tables; plots
ProgrammeRéseau des laboratoires scientifiques de la CGC, GEM : La géocartographie de l'énergie et des minéraux
Diffusé2013 04 30
Résumé(disponible en anglais seulement)
The eastern Himalaya is characterized by a region of granulites and local granulitized eclogites that have been exhumed via isothermal decompression from lower crustal depths during the India-Asia collision. Spatially, most of these regions are proximal to the South Tibetan detachment system, an orogen-parallel normal-sense detachment systemthat operated during theMiocene, suggesting that it played a role in their exhumation. Here we use geo- and thermochronological methods to study the deformation and cooling history of footwall rocks of the South Tibetan detachment system in northern Sikkim, India. These data demonstrate that the South Tibetan detachment systemwas active in Sikkim between 23.6 and ~13Ma, and that footwall rocks cooled rapidly from ~700 to ~120 \'01C between ~15-13Ma. While active, the South Tibetan detachment system exhumed rocks from mid-crustal depths, but an additional heat source such as strain heating, advected melt and/or crustal thinning is required to explain the observed isothermal decompression. Cessation of movement on the South Tibetan detachment system produced rapid cooling of the footwall as isotherms relaxed. A regional comparison of temperature-time data for the eastern South Tibetan detachment system indicates a lack of synchronicity between the Sa'er-Sikkim-Yadong section and the NW Bhutan section. To accommodate this requires either strike-slip tear faulting or local outof-sequence thrusting in the younger segment of the orogen.