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TitleStructure and kinematic evolution of the Duke River fault, southwestern Yukon
AuthorCobbett, R; Israel, S; Mortensen, J K; Joyce, N; Crowley, J L
SourceCanadian Journal of Earth Sciences 2016., https://doi.org/10.1139/cjes-2016-0074
Year2016
Alt SeriesEarth Sciences Sector, Contribution Series 20160155
PublisherNRC Research Press
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceAlberta; British Columbia; Northwest Territories; Yukon
NTS82K; 82L; 82M; 82N; 83C; 83D; 83E; 83F; 83K; 83L; 83M; 83N; 84C; 84D; 84E; 84F; 84K; 84L; 84M; 84N; 85C; 85D; 85E; 85F; 85K; 85L; 85M; 85N; 86C; 86D; 86E; 86F; 92I; 92J; 92K; 92L; 92M; 92N; 92O; 92P; 93; 94; 95; 96A; 96B; 96C; 96D; 96E; 96F; 96G; 96H; 102I; 102O; 102P; 103; 104; 105; 106A; 106B; 106C; 106D; 106E; 106F; 106G; 106H
Lat/Long WENS-156.0000 -116.0000 66.0000 50.0000
Subjectsgeochronology; igneous and metamorphic petrology; structural geology; metamorphism; deformation; foliation; greenschist facies; terranes; faults; faults, thrust; argon argon dating; argon argon dates; continental margins
Illustrationslocation maps; stratigraphic columns; geological sketch maps; cross-sections, stratigraphic; photographs; bar graphs; tables
ProgramWestern Cordillera, Redefinition of crustal blocks, GEM2: Geo-mapping for Energy and Minerals
AbstractIn southwest Yukon, the boundary between the Alexander terrane and Wrangellia corresponds with the Duke River fault. Although a substantial amount of new data has been collected about each of the terranes and their relationship with western North American, little is known about the nature and timing of movement on the Duke River fault. In this paper, we report on observations of the Duke River fault from three localities in southwest Yukon, and provide new constraints on the nature and timing of deformation. Within these areas, the Duke River fault juxtaposes imbricated, pervasively foliated and folded greenschist -facies rocks of the Alexander terrane southwest of the fault against, sub-greenschist- facies, less deformed rocks of Wrangellia. Multiple lines of evidence indicate the Alexander terrane has been juxtaposed against Wrangellia along a southwest-dipping thrust fault. 40Ar/39Ar dates from muscovite, inferred to have grown during faulting or to have been reset by motion along the Duke River fault, range from 83-105 Ma, suggesting that ductile movement along the fault is at least as old as mid-Cretaceous. This phase of faulting is interpreted as the local expression of mid- to Late Cretaceous shortening which has been documented the length and width of the Cordillera. Mid- to Late Cretaceous structures along the Duke River fault are overprinted by brittle deformation that affects rocks as young as Miocene (or Pliocene?). Beginning in the Miocene, subduction of the Yakutat block below southern Alaska caused rapid uplift of the Saint Elias Mountains in Yukon and Alaska. Shortening is currently occurring in southwest Yukon in response to this subduction and is evidenced by GPS motion vectors and microseismicity. The Duke River fault appears to be accommodating present day shortening through uplift and reactivation of the thrust fault.
Summary(Plain Language Summary, not published)
In southwest Yukon, the boundary between the Alexander terrane and Wrangellia lies along the Duke River fault. In this paper, we present observations of the Duke River fault from three localities in southwest Yukon, and provide new constraints on the nature and timing of faulting. The Duke River fault juxtaposes deformed low-grade metamorphic rocks of the Alexander terrane against lower grade and less deformed rocks of Wrangellia. Argon isotopic dates of muscovite from within the Duke River fault suggest that ductile movement along the fault took place at least 83-105 million years ago. This faulting is interpreted to have occurred during crustal shortening which has been documented throughout the Cordilleran mountain belt. Ductile fault structures have been overprinted by 3 to 23 million year-old brittle structures, which formed as the Yakutat tectonic plate sank beneath southern Alaska and caused rapid uplift of the Saint Elias Mountains in Yukon and Alaska. Frequent small earthquakes and GPS measurements in the region indicate that the Duke River fault is still presently active.
GEOSCAN ID299159