| Titre | Late Paleozoic assembly of the Alexander-Wrangellia-Peninsular composite terrane, Canadian and Alaskan Cordillera |
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| Auteur | Beranek, L P; van Staal, C R; McClelland, W C; Joyce, N ; Israel, S |
| Source | Geological Society of America Bulletin vol. 126, no. 11-12, 2014 p. 1531-1550, https://doi.org/10.1130/31066.1 |
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| Année | 2014 |
| Séries alt. | Secteur des sciences de la Terre, Contribution externe 20140045 |
| Éditeur | Geological Society of America |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1130/31066.1 |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Province | Yukon |
| Région | St-Elias Mountains; Alaska; Donjek Glacier suite; Barnard Glacier |
| Lat/Long OENS | -142.0000 -138.0000 62.0000 59.0000 |
| Sujets | terrains; analyses spectrométriques; datations au uranium-plomb; géochimie du niobium; géochimie du strontium; antécédents tectoniques; géologie structurale; géologie générale; géochronologie; Permien;
Paléozoïque |
| Illustrations | cartes de localisation; diagrammes; photographies; graphiques; diagrammes de distribution des éléments |
| Programme | GEM : La géocartographie de l'énergie et des minéraux Gisements polymétalliques - nord-ouest de la Cordillère canadienne (Yukon et
Colombie-Britannique) |
| Diffusé | 2014 06 23 |
| Résumé | (disponible en anglais seulement)
Late Paleozoic assembly of the Alexander- Wrangellia-Peninsular composite terrane is recorded by two phases of regional deformation, metamorphism, and magmatism
within basement complexes of the Alexander (Craig and Admiralty subterranes), Wrangellia, and Peninsular terranes in the Canadian and Alaskan Cordillera. New secondary ion mass spectrometry (SIMS) and chemical abrasionisotope dilution-thermal
ionization mass spectrometry (CA-ID-TIMS) zircon U-Pb ages, whole-rock major- and trace-element and Nd-Sr isotope geochemical compositions, and geological fi eld observations of late Paleozoic igneous rocks were used to identify the precise timing
and signifi cance of this tectonism in the Saint Elias Mountains region of southwestern Yukon and eastern Alaska. Middle to Late Pennsylvanian (301-307 Ma) igneous rocks, herein assigned to the Barnard Glacier suite, were preferentially emplaced
along the Wrangellia-Craig subterrane boundary and mainly comprise syenitic plutons that intrude Paleozoic country rocks with evidence of Pennsylvanian or older (D1) deformation. We propose that Barnard Glacier suite magmatism was produced by a slab
breakoff event after the consumption of a narrow backarc ocean basin and early Pennsylvanian collision between the Wrangellia- Peninsular arc and Craig subterrane passive margin. Early Permian (284-291 Ma) dioritic to granodioritic rocks, herein
assigned to the Donjek Glacier suite, comprise the vestiges of an extensive magmatic system within the Craig subterrane of southwestern Yukon and southeastern Alaska. The available data suggest that the Donjek Glacier suite represents part of a
short-lived, Early Permian arc that initiated along the outboard margin of the Craig subterrane-Wrangellia-Peninsular block after Pennsylvanian collision and slab breakoff. At two fi eld localities in southwestern Yukon, Paleozoic country rocks with
D1 fabrics are also intruded by sills and dikes of the Donjek Glacier suite that show evidence of ca. 285 Ma regional deformation and metamorphism (D2). Field evidence for Early Permian tectonism in the Saint Elias Mountains implies direct
connections with coeval deformation and metamorphism in the Admiralty subterrane, a microcontinent in the Admiralty Island region of southeastern Alaska that developed separately from the Craig subterrane prior to the Early Per mian. D2 tectonism was
likely related to the entry of the Admiralty subterrane margin into the Early Permian subduction zone, which resulted in collision and fi nal amalgamation of the Alexander-Wrangellia-Peninsular composite terrane. Our tectonic scenarios require the
currently accepted confi guration of the Alexander terrane (com posite of the Craig and Admiralty subterranes) to have only existed after the Early Permian collision between the Admiralty subterrane and the previously assembled Craig subterrane-
Wrangellia-Peninsular terrane. Biogeographic and other geological data suggest that the two-part assembly of the Alexander- Wrangellia-Peninsular composite terrane took place along a convergent margin to the north of the Cordilleran pericratonic arc
terranes (Yukon-Tanana, Quesnellia, and others ), in between the paleo -Pacifi c Ocean and paleo-Arctic Ocean realms, to the northwest of the supercontinent Pangea. The assembly of the Alexander-Wrangellia-Peninsular composite terrane might have been
associated with the Early to Middle Permian subduction polarity fl ip recognized in the Cordilleran pericratonic realm, which led to the closure of a backarc ocean basin and Late Permian arc-continent collision along the western margin of North
America. |
| Sommaire | (Résumé en langage clair et simple, non publié)
La géochronologie des unités de roches intrusives indique quand et comment divers terranes du superterrane insulaire se sont assemblés pour
former la partie ouest de la Cordillère canadienne au Yukon et dans le nord de la Colombie-Britannique. Pendant la période s'échelonnant du Crétacé moyen au Paléozoïque tardif, les terranes se sont déplacés par translation depuis l'océan
paléo-Arctique, où ils se sont formés, à l'océan paléo-Pacifique. Les terranes insulaires renferment de nombreux gisements de minéraux dont on peut maintenant lier la formation directement à leur évolution tectonique. |
| GEOSCAN ID | 293948 |
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