| Titre | Detrital zircon Hf isotopic compositions indicate a northern Caledonian connection for the Alexander terrane |
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| Auteur | Beranek, L P; van Staal, C R; McClelland, W C; Israel, S; Mihalynuk, M |
| Source | Lithosphere vol. 5, no. 2, 2012 p. 163-168, https://doi.org/10.1130/L255.1  Accès ouvert |
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| Année | 2012 |
| Séries alt. | Secteur des sciences de la Terre, Contribution externe 20120270 |
| Éditeur | Geological Society of America |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1130/L255.1 |
| Media | papier; en ligne; numérique |
| Formats | pdf; html |
| Province | Colombie-Britannique; Yukon |
| SNRC | 114O; 115B/02; 115B/03; 115B/04; 115B/05; 115C/01; 115C/02; 115C/07; 115C/08; 115C/09 |
| Région | Alaska; Saint Elias Mountains |
| Lat/Long OENS | -141.0000 -138.0000 61.7500 59.0000 |
| Sujets | tectonique de plaques; milieux tectoniques; interprétations tectoniques; marges plaques; cadre tectonique; modèles tectoniques; lithosphère; datations au zircon; zircon; datations au uranium-plomb;
datation au uranium-plomb; datations radiométriques; Terrane d'Alexander ; Caledonie; géochronologie; stratigraphie; tectonique; Protérozoïque; Paléozoïque; Jurassique |
| Illustrations | cartes de localisation; graphiques; échelles stratigraphiques; histogrammes |
| Programme | GEM : La géocartographie de l'énergie et des minéraux Gisements polymétalliques - nord-ouest de la Cordillère canadienne (Yukon et
Colombie-Britannique) |
| Diffusé | 2013 04 01 |
| Résumé | (disponible en anglais seulement)
Various plate reconstructions predict that the Alexander terrane, a Neoproterozoic - Jurassic crustal fragment now located in the North
American Cordillera,
evolved in proximity to the northern Appalachian-Caledonian convergent margin during assembly of supercontinent
Laurussia. To test stratigraphic connections with Laurussia that are implied by these plate reconstructions, we measured the Hf
isotopic
compositions of 176 detrital zircons from two relevant sedimentary sequences of the Alexander terrane. An older, Upper Silurian - Lower Devonian terrestrial to shallow-marine molasse sequence yields 405–490 Ma detrital zircons with
negative EHf(t) values and Mesoproterozoic to Paleoproterozoic Hf model ages. In combination with paleomagnetic and biogeographic constraints, these Hf data argue for the molasse strata to be now-displaced equivalents of the Old Red Sandstone and
primarily sourced from crustally contaminated granitoids in the Greenland, Svalbard, or British Caledonides. Late Silurian - Early Devonian orogenesis in the Alexander terrane is therefore likely related to the Scandian-Salinic phase of
Appalachian-Caledonian mountain building. Younger, Middle Devonian sequences of the Alexander terrane are endowed in 390 - 490 Ma detrital zircons with positive EHf(t) values and Neoproterozoic Hf model ages. These isotopic signatures are consistent
with the erosion of local basement rocks during the opening of the Slide Mountain - Angayucham backarc rift and tectonic separation of the Alexander terrane from northern Laurussia. |
| GEOSCAN ID | 291969 |
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