LA-ICP-MS uranium-lead geochronologic data of detrital zircon from a metamorphic rock in the northern Fairbanks mining district, Circle Quadrangle, Alaska, Raw Data File 2025-16, provides uranium-lead (U-Pb) geochronologic single spot zircon data, analyzed using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The detrital zircon (DZ) data come from a metamorphic rock from the Alaska Division of Geological & Geophysical Surveys' (DGGS) geologic mapping project in the northern Fairbanks mining district, covering parts of the Circle A-4, A-5, B-4, and B-5 quadrangles, Alaska. Sample 07JEA354a was collected by the DGGS Mineral Resources Section during a detailed geologic mapping campaign in June 2007. The zircon grain data table contains isotopic and elemental data for each zircon spot analyzed. Both tables have accompanying data dictionaries. These data and report are available from the DGGS website: http://doi.org/10.14509/31685.

Zircon geochronology of Torok and Nanushuk Formations sandstones at Slope Mountain and a Seabee Formation tephra deposit at Ninuluk Bluff, central North Slope, Alaska, Raw Data File 2024-33, presents LA-ICPMS and CA-ID-TIMS U-Pb data for five DZ samples collected from a well-known exposure at Slope Mountain, which is one of the few localities where the transition between mid-Cretaceous Torok and Nanushuk Formations is preserved in outcrop. We also report new U-Pb tephra zircon data from basal Seabee Formation at Ninuluk Bluff, a key-and similarly rare-site where the transition between Late Cretaceous Nanushuk strata and overlying Seabee crops out. These tandem-dated samples were collected during summer field seasons in 2018 and 2019 as part of DGGS's North Slope and Brooks Range foothills basin analysis program. The new zircon geochronology results from Slope Mountain and Ninuluk Bluff are documented and permanently archived herein. These data and report are available from the DGGS website: http://doi.org/10.14509/31152.

This Alaska Division of Geological & Geophysical Surveys (DGGS) Raw Data File presents U-Pb zircon geochronology results from igneous, meta-igneous, and metasedimentary rocks collected during the Tok River and Wrangellia geologic mapping projects in the eastern Alaska Range and the northwestern Talkeetna Mountains. The purpose of these analyses is to better constrain the age of select geologic units encountered during the mapping projects. The samples were submitted to the U.S. Geological Survey, Geology, Geophysics, and Geochemistry Science Center (GGGSC)-Plasma Lab in Denver, CO where U-Pb geochronology analyses were performed by Christopher Holm-Denoma in 2016-2017. All files are available from the DGGS website: http://doi.org/10.14509/30439.

Twenty-two igneous and metamorphic rock samples were collected in a 20-km-long swath centered on the Alaska Highway between Tetlin Junction, Alaska, and the Canada border. Igneous and metamorphic rock samples were submitted to the Apatite to Zircon, Inc. laboratory (A2Z), where zircon U-Pb age analysis, using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), was performed by Paul O'Sullivan. The 15 felsic plutonic rock samples and one gabbro sample yield Cretaceous zircon U-Pb weighted-mean ages ranging from 95.7 Ma to 106.2 Ma. Zircons from a metadiorite yield a Triassic weighted-mean age of about 241.9 Ma. Metamorphic zircons from two samples with felsic igneous protoliths yield Mississippian weighted-mean ages of 351.7 Ma and 354.6 Ma. Detrital zircons from two metaconglomerates yield individual grain ages from 100 Ma to 1,811 Ma, but are predominantly between 300 Ma and 345 Ma. Detrital zircons from a quartzite yield peaks at about 2,648 Ma, 1,946 Ma, and 1,807 Ma. Samples were analyzed for a variety of suites of major and trace elements depending on the sample type. The analytical data tables associated with this report are being released in digital format.

This Alaska Division of Geological & Geophysical Surveys (DGGS) Preliminary Interpretive Report presents uranium-lead (U-Pb) ages of zircons from 37 igneous and metamorphic samples collected during the 2019 field season in support of a 4,800-sq-km (1,860-sq-mi) bedrock geologic map of eastern Interior Alaska surrounding Mount Fairplay and the Ladue River drainage. The area lies north of the Alaska Highway and is approximately 65 km (40 mi) east of Tok, Alaska; it runs west from the Alaska-Yukon border to encompass the Taylor Highway. DGGS and U.S. Geological Survey (USGS) staff identified this area as having underexplored potential to host deposits of critical minerals, including rare earth elements (REE), uranium, niobium, zirconium, tin, tungsten, bismuth, and rhenium, as well as conventional mineral resources including gold, copper, molybdenum, lead, zinc, and silver. The goal of this U-Pb isotopic study is to better understand the Devonian through Paleogene magmatic and tectonic events, which have been linked to most of the known mineralization in the Yukon-Tanana Uplands. The Mount Fairplay and Ladue River areas are characterized by amphibolite- to greenschist-facies metamorphic rocks-the Lake George assemblage, Ladue River unit, and the Klondike assemblage-which have Mississippian-Devonian and Permian protolith ages. Voluminous volcanic and plutonic rocks of varying composition and texture from the mid-Cretaceous (ca. 100-115 Ma), Late Cretaceous (ca. 65-71 Ma), and Paleogene (ca. 57-58 Ma) magmatic episodes were observed to be emplaced in both the Lake George and Ladue River metamorphic units. Alaska DGGS and the USGS staff have identified both generations of Cretaceous magmatism as having potential to host deposits of the critical minerals mentioned above. All components of this data release are available on the DGGS website: http://doi.org/10.14509/30732.

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 dataset includes U-Pb detrital zircon age data for samples from the Ingleside and Lyons formations in north-central Colorado collected from Owl Canyon and Park Creek Reservoir, from the Molas and Hermosa formations in southwestern Colorado collected from Molas Pass, and from the Lykins formation and its equivalents along the Front Range and in southeastern Colorado. It accompanies publications 'The Permian-Triassic Transition in Colorado' published in Unfolding the Geology of the West: Geological Society of America Field Guide 44, and 'Detrital zircon geochronology of Pennsylvanian-Permian strata in Colorado: evidence for Appalachian-derived sediment and implications for the timing of Ancestral Rocky Mountains uplift' published in The Mountain Geologist.

This dataset includes U-Pb detrital zircon age data for samples from the Ingleside and Lyons formations in north-central Colorado collected from Owl Canyon and Park Creek Reservoir, from the Molas and Hermosa formations in southwestern Colorado collected from Molas Pass, and from the Lykins formation and its equivalents along the Front Range and in southeastern Colorado. It accompanies publications 'The Permian-Triassic Transition in Colorado' published in Unfolding the Geology of the West: Geological Society of America Field Guide 44, and 'Detrital zircon geochronology of Pennsylvanian-Permian strata in Colorado: evidence for Appalachian-derived sediment and implications for the timing of Ancestral Rocky Mountains uplift' published in The Mountain Geologist.

During the 2017 and 2018 field seasons, geologists from the Alaska Division of Geological & Geophysical Surveys (DGGS) conducted geologic mapping and sampling in the Richardson mining district southeast of Fairbanks, including parts of the Big Delta B-4, B-5, B-6, and C-6 quadrangles. The project area has produced approximately 122,000 ounces of gold, mostly from placer mines, and includes the Uncle Sam, Montecristo, Richardson, Tower, and Hilltop lode gold exploration properties. The goal of DGGS's work in this area is to conduct a mineral-resource assessment and to build an improved understanding of the area's geology and controls on gold mineralization to facilitate industry exploration targeting. Uranium-lead (U-Pb) zircon geochronology results presented in this report show that similarly textured quartz-feldspar porphyry intrusions in the project area were generated by both Paleocene (56.8 +/- 0.9 Ma; 18WCW149) and middle Cretaceous (92.0 +/- 0.7 Ma; 18AW002, known as the Democrat Dike) magmatic episodes. The ages of medium-grained plutonic rocks at Birch Lake (92.4 +/- 0.6 Ma; 18ET587) and Gold Run (93.7 +/- 0.7 Ma; 18ET580) lie within error of the age of the hypabyssal Democrat Dike, indicating that the present-day depth of exposure juxtaposes rocks that were buried at widely different crustal depths during the middle Cretaceous. Phaneritic granodiorite near the Democrat prospect yielded a zircon age of 110.7 +/- 1.3 Ma (18RN565), extending the magmatic history of the prospect into the Early Cretaceous. Amphibolite-facies augen orthogneiss yielded a Late Devonian zircon age of 364.5 +/- 6.0 Ma (18ET040), consistent with similar rocks in the Lake George assemblage. Detrital zircons analyzed from siliciclastic schist along the Richardson Highway (18AW021) contain prominent age populations at 1.8 and 2.6 Ga, consistent with a Laurentian cratonic source and consistent with other results from parautochthonous North America. Pelitic schist from the Hilltop prospect (18TJN372) yielded a relatively small number (n=32) of zircon grains that define small age populations between ca. 1.7 and 1.5 Ga. All components of this data release are available on the DGGS website: http://doi.org/10.14509/30555.

This Alaska Division of Geological & Geophysical Surveys (DGGS) Preliminary Interpretive Report presents U-Pb ages of zircons from 14 sedimentary, metamorphic, and igneous samples collected during 2017 and 2018 field investigations in the northeastern Tanacross Quadrangle, Alaska. The DGGS Northeast Tanacross project is a part of multi-year effort to investigate the geology and mineral-resource potential of the Yukon-Tanana Uplands region in collaboration with the U.S. Geological Survey. The purpose of the U-Pb isotopic study is to better understand the Devonian-to-Mississippian and Mesozoic-to-Early Paleogene episodes of magmatic and tectonic events within the Yukon-Tanana Uplands and the relationship of magmatism to the metallic mineral deposits. This area is characterized by the presence of two Late Devonian to Mississippian metamorphic assemblages--Lake George and Fortymile River. Both assemblages are composed of metasedimentary and metavolcanic rocks that have been intruded by Devonian to Eocene intrusive rocks of varying composition and texture. Paleozoic intrusive rocks are deformed and metamorphosed and include prevalent Late Devonian-Early Mississippian augen orthogneiss, herein called the Divide Mountain suite, that was emplaced into and deformed together with the Lake George assemblage. The Fortymile River assemblage is primarily cross cut by Mississippian to Permian intrusive rocks that are also pervasively deformed and metamorphosed. Following Jurassic to mid-Cretaceous regional metamorphism and deformation, all metamorphic rock packages were intruded by Mid- to Late-Cretaceous volcanic and plutonic rocks, some of which have known or suspected potential for gold together with silver, zinc, copper, and lead mineralization. Products included in this data release are: A summary of sample-collection methods, the laboratory report, analytical data tables, and associated metadata. All components of this data release are available on the DGGS website: http://doi.org/10.14509/30465.