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Accueil du site > Français > Les annonces de séminaires et thèses > Séminaire de Johan DE GRAVE (Ghent University)

Séminaire de Johan DE GRAVE (Ghent University)

Date : 03 juin 2013, 10 h 30

Titre : Building and evolution of the Kyrgyz Tien Shan : constraints from multi-method (thermo)chronology.

Lieu : Salle de Conférences de l’OSUR (Bât. 14 B, RdC)

Résumé :

Crystalline basement across terrane boundaries was sampled during several field trips with the aim of establishing a geo- and thermochronological framework for the Kyrgyz Tien Shan and reconstructing its thermo-tectonic evolution in an absolute time frame. A multi-method chronological strategy was implemented to achieve this objective : low-temperature thermochronology is coupled to geochronological methods characterized by higher closure temperatures, including zircon U/Pb and ZHe, biotite and muscovite 40Ar/39Ar, titanite fissiontrack, K-feldspar 40Ar/39Ar, and apatite fission track and AHe. This array of techniques allows us to establish the formation or emplacement ages of the ancestral Tien Shan basement and to pinpoint the recent exhumation of the basement during the building of the modern Tien Shan. Although local differences are to be observed, a consistent picture for the Kyrgyz Tien Shan emerges :
1) Emplacement of granitoid basement in the North Tien Shan during the Ordovician–Silurian (460-420 Ma) ;
2) Final amalgamation of the ancestral Kyrgyz Tien Shan in the Late Carboniferous–Early Permian (300 Ma) ;
3) A phase of Permian (290-270 Ma) postcollisional magmatic activity ;
4) The subsequent Mesozoic exhumation of the basement ;
5) Distinct Cimmerian collision-accretion events linked to the closure of the Tethys ;
6) Finally, the initiation of the active building of the modern Tien Shan in the Late Oligocene-Early Miocene as a distant effect of ongoing indentation of the Indian plate in Eurasia.

Low-T thermocronology data for the Kyrgyz Tien Shan study areas in relation to tectonic reactivation