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Late Cretaceous to Paleocene Tectonometamorphic Evolution of the Blanchard River Assemblage, Southwest Yukon: New Insight into the Terminal Accretion of Insular Terranes in the Northern Cordillera

Resource type
Date created
2020-09-21
Authors/Contributors
Author (aut): Vice, Lianna
Author (aut): Gibson, H. Daniel
Author (aut): Israel, Steve
Abstract
The Intermontane-Insular terrane boundary stretches over 2000 kilometers from British Columbia to Alaska in the western Cordillera. Juxtaposed between these terranes is a series of Jura-Cretaceous basinal and arc assemblages that record a complicated and contested tectonic evolution related to the Mesozoic-Paleocene accretionary history of northwestern North America. In southwest Yukon, west-verging thrust faults facilitated structural stacking of the Yukon-Tanana terrane over these basinal assemblages, including the Early Cretaceous Blanchard River assemblage. These previously undated compressional structures are thought to be related to the final collapse of the Jura-Cretaceous basins and the tectonic burial of the Blanchard River assemblage resulting in amphibolite facies metamorphism. New in situ U-Th-Pb monazite ages record at least three tectonic events: (1) the tectonic burial of the Blanchard River assemblage to amphibolite facies conditions between 83 and 76 Ma; (2) peak burial was followed by regional exhumation at ca. 70-68 Ma; and (3) intense heating and ca. 63-61 Ma low-pressure contact metamorphism attributed to the intrusion of the voluminous Ruby Range suite, which is part of the northern Coast Mountains batholith. The tectonometamorphic evolution recorded in the Blanchard River assemblage can be correlated to tectonism within southwest Yukon and along the length of the Insular-Intermontane boundary from western British Columbia through southwestern Yukon and Alaska. In southwest Yukon, these results suggest an asymmetric final collapse of Jura-Cretaceous basins during the Late Cretaceous, which relates to the terminal accretion of the Insular terranes as they moved northward.
Document
Identifier
DOI: 10.2113/2020/2298288
Published as
Vice, L., Gibson, H. D., & Israel, S. (2020). Late Cretaceous to Paleocene Tectonometamorphic Evolution of the Blanchard River Assemblage, Southwest Yukon: New Insight into the Terminal Accretion of Insular Terranes in the Northern Cordillera. Lithosphere, 2020(1), 1–22. https://doi.org/10.2113/2020/2298288
Publication title
Lithosphere
Document title
Late Cretaceous to Paleocene Tectonometamorphic Evolution of the Blanchard River Assemblage, Southwest Yukon: New Insight into the Terminal Accretion of Insular Terranes in the Northern Cordillera
Date
2020
First page
1
Last page
22
Copyright statement
Copyright is held by the author(s).
Scholarly level
Peer reviewed?
Yes
Language
English
Member of collection
Download file Size
2298288.pdf 10.45 MB

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