| Titre | (U-Th)/He thermochronology of the Klondike Plateau, Dawson Range and Aishihik Batholith, central Yukon: resolving the timing of shallow crustal tectonism |
| |
| Auteur | Moher, M E; Powell, C D; Schneider, D A; Ryan, J J; Joyce, N L |
| Source | Margins through time : GAC-MAC 2016; Association géologique du Canada-Association minéralogique du Canada, Réunion annuelle, Programme et résumés vol. 39, 2016 p. 66  Accès ouvert |
| Liens | Online - En ligne (complete volume - volume
complet, PDF, 1.3 MB)
|
| Année | 2016 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20190371 |
| Éditeur | Association géologique du Canada |
| Réunion | GAC-MAC 2016; Whitehorse, YK; CA; juin 1-3, 2016 |
| Document | publication en série |
| Lang. | anglais |
| Media | en ligne; numérique |
| Formats | pdf |
| Province | Yukon |
| Région | Klondike Plateau; Dawson Range |
| Sujets | Batholite d'Aishihik ; géochronologie; tectonique; Sciences et technologie; Nature et environnement |
| Programme | GEM2 : La géocartographie de l'énergie et des minéraux Redéfinition des blocs de la croûte terrestre de l'ouest de la Cordillère |
| Diffusé | 2016 06 01 |
| Résumé | (disponible en anglais seulement)
During the Late Paleozoic through the Cenozoic, terranes were episodically accreted onto the western margin of North America. Zircon and apatite (U-Th)/He
thermochronologic investigations of the Yukon-Tanana terrane (YTT) and successor rocks can provide insight into the low-temperature (<200°C) window of Jurassic- Cretaceous tectonism and crustal exhumation. Samples were collected in an attempt to
build a network of low-temperature thermochronometers across the major faults and crustal blocks to resolve their crustal levels during mineralization episodes in the region. For the study, we attempted to sample plutonic bodies that are
characterized by low ductile strain, possess single populations of zircon and apatite (exhibiting typical igneous zoning and lacking metamorphic overgrowths), and likely have straightforward cooling histories. Thirty Paleozoic and Mesozoic granitoids
were sampled from the Klondike Plateau and in the Dawson Range south of the Tintina fault, and ten granitoid samples were collected from the Jurassic Aishihik batholith (190-180 Ma), southeast of the Dawson Range. The nature of the northwestern
contact of the Aishihik batholith is equivocal, and samples have been taken on either side to investigate whether it is a structural discontinuity. Although proposed to be structurally emplaced via thrusting against Yukon- Tanana terrane, recent
mapping suggests that the northwestern margin of the Aishihik batholith is an intact intrusive contact, which has implications for the level of crust that is preserved from Jurassic time. Preliminary zircon (U-Th)/He analysis for samples from the
Klondike Plateau and Dawson Range yield single grain dates that reflect an age dispersion between Early Jurassic to Early Eocene that exhibit a relationship with effective uranium (eU), a proxy for radiation damage. The cooling ages generally can be
resolved into a domainal pattern, which is defined by fault-bounded crustal blocks that become progressively younger towards the southwest. Zircon cooling (~180°C) dates in the central Klondike Plateau are >135 Ma; samples west of the Teslin fault
have cooling ages <110 Ma, whereas west of the Yukon River, which possibly follows a strand of the Teslin fault, samples have cooling ages that are <75 Ma. We are testing whether the the (U-Th)/He age pattern that is evident in the Dawson Range
extends southward, to the region of the Aishihik batholith, or if an older (eg. Jurassic to mid-Cretaceous) exhumation history is preserved. |
| GEOSCAN ID | 321646 |
|
|