The Reid Lakes batholith (RLB) in southwestern McQuesten map area (115P) has previously been tentatively assigned a mid-Cretaceous age, although two K-Ar ages from the northwestern part of the batholith indicated that at least part of the body must be late Paleozoic or older. U-Pb dating of two lithologically distinct samples from the southeastern part of the RLB yields Early Mississippian crystallization ages (341.5 ± 0.7 Ma and 355.7 ± 0.9 Ma). A sample of the Moose Creek pluton, which is on the northeast side of the Tintina fault zone, but was previously interpreted to be part of the RLB, yielded a U-Pb age of 92.0 ± 0.3 Ma. The Moose Creek pluton is therefore correlated with the mainly 95-93 Ma South Lansing plutonic suite which intrudes rock units of Ancestral North America, whereas the RLB is a multi-phase, Early Mississippian intrusion into metamorphic rocks of the Yukon-Tanana terrane.

This data release contains three tables of U-Pb zircon isotopic data generated from analyses of 40 metaplutonic and metavolcanic rocks from the Yukon-Tanana Upland of western Yukon and east-central Alaska and one sample from southern Yukon. One of the tables also reports U-Pb data for two titanite analyses for one of the samples. U-Pb zircon ages from analyzed samples range from 363.5 ± 3.8 to 253.1 ± 0.7 Ma and were collected from parautochthonous North America and the allochthonous Yukon-Tanana terrane. U-Pb zircon data include 216 individual analyses by ID-TIMS and 35 individual analyses of two samples by LA-ICP-MS. ID-TIMS analyses of titanite give concordant 206Pb-238U ages of 333 and 338 Ma. Two U-Pb tables report the isotopic composition of uranium (U) and thorium (Pb) measured in each grain, ratios of isotopes of lead and uranium isotopes, and the age of each grain. A third table reports interpreted U-Pb ages, sample locations, tectonic assemblage or unit, lithology, analysis method, laboratory used, and basis for age assignment. The data release also contains two tables of whole-rock major- and trace-element geochemical data for metaigneous rocks from the Yukon-Tanana Upland in east-central Alaska for augen gneiss (15 samples) and amphibolite (30 samples).

This data release contains three tables of U-Pb zircon isotopic data generated from analyses of 40 metaplutonic and metavolcanic rocks from the Yukon-Tanana Upland of western Yukon and east-central Alaska and one sample from southern Yukon. One of the tables also reports U-Pb data for two titanite analyses for one of the samples. U-Pb zircon ages from analyzed samples range from 363.5 ± 3.8 to 253.1 ± 0.7 Ma and were collected from parautochthonous North America and the allochthonous Yukon-Tanana terrane. U-Pb zircon data include 216 individual analyses by ID-TIMS and 35 individual analyses of two samples by LA-ICP-MS. ID-TIMS analyses of titanite give concordant 206Pb-238U ages of 333 and 338 Ma. Two U-Pb tables report the isotopic composition of uranium (U) and thorium (Pb) measured in each grain, ratios of isotopes of lead and uranium isotopes, and the age of each grain. A third table reports interpreted U-Pb ages, sample locations, tectonic assemblage or unit, lithology, analysis method, laboratory used, and basis for age assignment. The data release also contains two tables of whole-rock major- and trace-element geochemical data for metaigneous rocks from the Yukon-Tanana Upland in east-central Alaska for augen gneiss (15 samples) and amphibolite (30 samples).

This data release contains three tables of U-Pb zircon isotopic data generated from analyses of 40 metaplutonic and metavolcanic rocks from the Yukon-Tanana Upland of western Yukon and east-central Alaska and one sample from southern Yukon. One of the tables also reports U-Pb data for two titanite analyses for one of the samples. U-Pb zircon ages from analyzed samples range from 363.5 ± 3.8 to 253.1 ± 0.7 Ma and were collected from parautochthonous North America and the allochthonous Yukon-Tanana terrane. U-Pb zircon data include 216 individual analyses by ID-TIMS and 35 individual analyses of two samples by LA-ICP-MS. ID-TIMS analyses of titanite give concordant 206Pb-238U ages of 333 and 338 Ma. Two U-Pb tables report the isotopic composition of uranium (U) and thorium (Pb) measured in each grain, ratios of isotopes of lead and uranium isotopes, and the age of each grain. A third table reports interpreted U-Pb ages, sample locations, tectonic assemblage or unit, lithology, analysis method, laboratory used, and basis for age assignment. The data release also contains two tables of whole-rock major- and trace-element geochemical data for metaigneous rocks from the Yukon-Tanana Upland in east-central Alaska for augen gneiss (15 samples) and amphibolite (30 samples).

not_specified

Paleozoic rocks of the Pelly Mountains, central Yukon, preserve greater than 150 m.y. of sedimentation, magmatism and base-metal mineralization. To identify secular trends in regional tectonics and metallogeny, a multi-year project on the stratigraphy of the Pelly Mountains in the Quiet Lake (105F) and Finlayson Lake (105G) map areas was initiated. Field studies during summer 2015 focused on two stratigraphic intervals: (1) mafic volcanic, volcaniclastic and clastic rock successions assigned to the Cambrian-Ordovician Cloutier and Groundhog formations (Kechika group); and (2) felsic volcanic, volcaniclastic and clastic rock successions assigned to the Devonian-Mississippian Black Slate and Felsic Volcanic formations (Seagull group). Cambrian-Ordovician strata were deposited in a marine environment characterized by episodic mafic volcanism and extensional tectonism. Devonian-Mississippian strata record the transition from an extensional turbidite basin to a metalliferous volcanic rift basin, and resemble key rock assemblages of the Selwyn basin (Earn Group) and Yukon-Tanana terrane (Grass Lakes and Wolverine Lake groups).

The geology in the Mount Nansen area, of the Dawson Range, comprises a metamorphic basement overlain and intruded by mid and Late Cretaceous magmatic rocks. Mid-Cretaceous epithermal deposits are recognized in the Brown-McDade cluster in the south, and Late Cretaceous porphyry and epithermal occurrences in the centrally located Klaza cluster. Here we report eight new U-Pb zircon crystallization ages, two CA-TIMS and six LA-ICPMS, and Pb isotopic data for igneous feldspar from six samples. A 199.06 ± 0.96 Ma crystallization age demonstrates the host rock to the Brown-McDade deposit is the Late Triassic to Early Jurassic Minto suite. We report crystallization ages of 111 ± 1.8 Ma for the Dickson Hill porphyry, 107.96 ± 0.03 and 107.86 ± 0.03 Ma for the central and border phases of the Bow Creek granite, respectively, and 107.0 ± 0.72, 107.0 ± 0.78 and 107.5 ± 0.67 Ma for equigranular and porphyritic phases of the Dawson Range granodiorite. These ages confirm a mid-Cretaceous Whitehorse suite affinity for these rocks with porphyritic textures suggesting high-level emplacement. Feldspar Pb isotopic data of igneous rocks in the Mount Nansen area become more radiogenic with time and are distinct for Late Triassic to Early Jurassic plutonic rocks versus Cretaceous rocks. Cretaceous feldspar isotopic data broadly overlaps Pb isotopic values of galena from deposits throughout the Dawson Range suggesting coeval magmatic rocks are a significant source of metals.

We report U-Pb zircon geochronology results for one metavolcanic and one metaplutonic rock sample from the Mount Hayes A-6 Quadrangle of central Alaska. These samples are representative of rock units assigned to the Clearwater terrane of Jones and others (1987), a sequence of greenschist-grade metavolcanic and metasedimentary rocks of poorly constrained age and tectonic origin. Our results indicate a crystallization age of 277.33 +/- 11.84 Ma for a felsic metavolcanic rock, and a 268.05 +/- 11.64 Ma crystallization age for a granitic metaplutonic unit intruding the former.

This data set contains U-Pb isotopic data and associated ages of detrital zircon from sedimentary and metasedimentary rocks collected in northern Yukon, Canada. The samples were originally collected as part of geological mapping and research conducted by the Geological Survey of Canada. They were recovered from archived collections and sent to the U.S. Geological Survey for analysis of detrital zircon using U-Pb geochronology methods. Detrital zircon grains were separated and analyzed by GeoSep Services (GSS) in 2015 using laser-ablation-inductively-coupled-plasma-mass spectrometry (LA-ICP-MS) techniques.

This data set contains U-Pb isotopic data and associated ages of detrital zircon from sedimentary and metasedimentary rocks collected in northern Yukon, Canada. The samples were originally collected as part of geological mapping and research conducted by the Geological Survey of Canada. They were recovered from archived collections and sent to the U.S. Geological Survey for analysis of detrital zircon using U-Pb geochronology methods. Detrital zircon grains were separated and analyzed by GeoSep Services (GSS) in 2015 using laser-ablation-inductively-coupled-plasma-mass spectrometry (LA-ICP-MS) techniques.