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TitleU-Pb geochronology, Nd-Sm geochemistry, structural setting, and tectonic significance of Late Devonian and Paleogene intrusions in northern Yukon and northeastern Alaska
AuthorLane, L SORCID logo; Mortensen, J K
SourceCanadian Journal of Earth Sciences vol. 56, no. 6, 2018 p. 585-606,
Alt SeriesNatural Resources Canada, Contribution Series 20180086
PublisherCanadian Science Publishing
Mediapaper; on-line; digital
RelatedThis publication is accompanied by U-Pb geochronology, geochemistry, and geological setting of Devonian and Eocene granitic intrusions of northern Yukon and adjacent Alaska: site and sample descriptions, data tables, and imagery
File formatpdf (Adobe® Reader®); html
NTS116N; 116O; 117A; 117B
AreaAlaska; Canada; United States of America
Lat/Long WENS-143.0000 -137.0000 69.0000 67.0000
Subjectsgeochronology; geochemistry; structural geology; tectonics; economic geology; paleontology; geophysics; Paleogene; Upper Devonian; tectonic setting; tectonic history; magmatism; intrusions; plutons; dykes; dykes, mafic; emplacement; deformation; foliation; cleavage; quartz veins; provenance; partial melting; volcanism; rifting; radiometric dating; uranium lead dating; zircon dates; isotopic studies; neodymium samarium dates; rubidium strontium dates; potassium argon dates; mass spectrometer analysis; bedrock geology; lithology; igneous rocks; intrusive rocks; granites; syenites; granodiorites; volcanic rocks; rhyolites; porphyries; volcaniclastics; mafic volcanic rocks; basalts; felsic volcanic rocks; sedimentary rocks; cherts; limestones; argillites; shales; sandstones; siltstones; conglomerates; dolostones; slates; metamorphic rocks; greenstones; phyllites; structural features; faults; faults, thrust; faults, normal; folds; anticlines; synclines; cupola; bedding planes; mineral occurrences; molybdenum; uranium; tungsten; skarns; garnet; epidote; fossils; geophysical interpretations; magnetic interpretations; aureoles; andalusite; whole rock geochemistry; major element analyses; trace element analyses; tectonic interpretations; Old Crow Basin; Bear Mountain Granite; Dave Lord Pluton; Angayucham Ocean Basin; Fitton Pluton; Hoidahl Cupola; Sedgwick Pluton; Kingak Formation; Ammerman Pluton; Old Crow Batholith; Schaeffer Pluton; Shublik Formation; Lisburne Group; Endicott Group; Bluefish Basin; Bear Mountain Intrusions; Echooka Formation; Kayak Formation; Kanayut Formation; Kekiktuk Formation; Hammond Subterrane; Coldfoot Subterrane; Kobuk Fault; Kaltag Fault; Tintina Fault; Phanerozoic; Cenozoic; Tertiary; Mesozoic; Cretaceous; Jurassic; Triassic; Paleozoic; Permian; Carboniferous; Devonian; Ordovician; Cambrian; Precambrian; Proterozoic
Illustrationslocation maps; geoscientific sketch maps; photographs; photomicrographs; tables; Concordia diagrams; bar graphs; geochemical plots
ProgramGEM2: Geo-mapping for Energy and Minerals Western Arctic Sverdrup Basin
Released2018 12 05
AbstractA suite of six Devonian granites and one syenite were emplaced into the upper crust of northern Yukon between 364.8 ± 2.7 and 371.2 ± 1.4 Ma. The Bear Mountain syenite and related rhyolite porphyry in adjacent Alaska intruded at 52.3 ± 0.4 and 53.5 ± 0.2 Ma, respectively. A felsic volcaniclastic unit and quartz-phyric sill are newly documented adjacent to the Mount Sedgwick granite. The volcaniclastic unit may indicate the presence of a related volcanic edifice. The presence of xenocrystic zircon grains in most of the intrusions suggests initial emplacement of magmas began 10-20 Myr before final emplacement into the upper crust. A Famennian final intrusion age coincides with Late Devonian encroachment of Ellesmerian deformation into the region. Attendant crustal flexure, or evolving foreland structures, may have facilitated upward migration of the magmas. Geochemistry of the intrusions indicates that the Devonian magmatism was largely derived from partial melting of lower and middle crust, implying widespread mafic magmatic underplating in Middle to Late Devonian time. Only Dave Lord syenite retains evidence of an original mantle geochemical signature. Mantle underplating may have played a role in localizing extension, volcanism, and rifting that led to the Late Devonian opening of the Angayucham ocean basin. The Eocene Bear Mountain pluton is inferred to be a northerly example of widespread Cenozoic within-plate magmatism in Alaska.
Summary(Plain Language Summary, not published)
We have investigated the age and chemistry of seven Late Devonian age granitic intrusions and one early Cenozoic age intrusion in northernmost Yukon and adjacent Alaska. Previously, their ages were poorly known. Using trace element chemistry we found that most of the intrusions were derived from partial melting of lower crustal rocks. This allows us to suggest how the intrusions may relate to plate tectonic processes active in the study area and across the broader Arctic region, at the time of the intrusions. Some of the intrusions are known to be associated with mineral showings.

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