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TitreDetrital zircon Hf isotopic compositions indicate a northern Caledonian history for the Alexander terrane
AuteurBeranek, L P; van Staal, C R; McClelland, W C; Israel, S; Mihalynuk, M
SourceLithosphere vol. 5, no. 2, 2012 p. 163-168,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20120270
ÉditeurGeological Society of America (GSA)
Documentpublication en série
Mediapapier; en ligne; numérique
Formatspdf; html
ProvinceColombie-Britannique; Yukon
SNRC114O; 115B/02; 115B/03; 115B/04; 115B/05; 115C/01; 115C/02; 115C/07; 115C/08; 115C/09
Lat/Long OENS-141.0000 -138.0000 61.7500 59.0000
Sujetstectonique 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
Illustrationslocation maps; plots; stratigraphic columns; histograms
ProgrammeGisements polymétalliques - nord-ouest de la Cordillère canadienne (Yukon et Colombie-Britannique), GEM : La géocartographie de l'énergie et des minéraux
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.