Moshrefzadeh, J.A.Naibert, T.J.Hofmann, FlorianNewberry, R.J.Twelker, EvanBuchanan, J.W.2026spreadsheetRaw Data FileRDF 2026-14Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys55 p.https://doi.org/10.14509/3208640Ar/39Ar geochronology data from the Big Delta and Circle quadrangles, Alaska, Raw Data File 2026-14, presents 40Ar/39Ar geochronology results acquired to support geologic mapping and mineral resource evaluation in the Big Delta and Circle quadrangles of Interior Alaska. During the 2023 field season, geologists from the Alaska Division of Geological & Geophysical Surveys conducted 1:100000 scale mapping across approximately 5750 square miles (15000 square kilometers) within the project area, funded by the U.S. Geological Survey Earth Mapping Resource Initiative program and the State of Alaska. The mapping targeted regions that include the operating Pogo mine, historical mining districts, active exploration projects, and areas with potential for future mineral resource development. Mineralization in the region includes structurally controlled and intrusion related gold systems, intrusion related tungsten and molybdenum prospects, and syngenetic lead zinc silver occurrences. The 22 40Ar/39Ar ages reported here were obtained from 21 samples collected within the Chena Project boundary and represent lithologies including metagrit, phyllite, gabbro, schist, granofels, amphibolite, quartz veins, lamprophyre, porphyry, paragneiss, orthogneiss, metagabbro, and granite. These ages were interpreted to refine the geologic history of the region and to better constrain the timing of mineralization and related tectonic events. These data and accompanying discussion are released as a DGGS Raw Data File, and all publication components are available from the DGGS website at: http://doi.org/10.14509/32086.The purpose of this research was to generate 40Ar/39Ar geochronology ages that improve understanding of the geologic history, tectonic evolution, and timing of mineralization within the Chena Project area of the Big Delta and Circle quadrangles. These age data were collected to support modern 1:100000 scale geologic mapping and to refine interpretations of structurally controlled and intrusion related mineral systems, including gold, tungsten, molybdenum, and syngenetic lead zinc silver occurrences. The results provide chronological constraints that strengthen ongoing efforts to evaluate mineral resource potential in Interior Alaska.>ArAr_data: Analytical lab data and accompanying data dictionary >ArAr_summary-data: Summary data spreadsheet and accompanying data dictionary20232026ground conditionCompleteNone planned-146.452067-144.32449565.18504064.378858ISO 19115 Topic CategorygeoscientificInformationAlaska Division of Geological & Geophysical Surveys40Ar/39ArAge DatesAmphiboliteAnalysesAnalyses and SamplingAnalytical Lab ResultsAnalytical ResultsAr-ArBedrockBedrock GeologyDGGSExplorationGabbroGeochronologyGeologicGeologyGraniteIsotopesMineral DevelopmentMineral ExplorationMineral ResourcesMineralsMiningMuscoviteOrthogneissOutcropPhylliteResourcesSample LocationSchistSericiteAlaska Division of Geological & Geophysical SurveysAnderson CreekAngel CreekBeaver CreekBlackshell CreekBoulder CreekCentral CreekChena RiverCircle Mining DistrictCrawford CreekDan CreekDemar CreekEmory CreekFairbanks Mining DistrictFar MountainFrozenfoot CreekGlacier CreekGlobe CreekGold CreekGoodpaster Mining DistrictJones PassLawson CreekMarten CreekMascot CreekMastadon CreekMunson CreekOhio CreekOlympia CreekOttertail CreekPine CreekPogoPorcupine CreekRicks CreekRock CreekRosebud CreekSalmonfoot CreekShamrock CreekShawnee PeakSonora CreekStone Boy CreekStuart CreekWickersham CreekWolverine CreekWalker, J.D., Geissman, J.W., Bowring, S.A, and Babcock, L.E., comp., 2012, Geologic Time Scale v. 4.0: Geological Society of AmericaAlbianAptianCretaceousEoceneHauterivianHettangianJurassicNorianPaleocenePaleogeneTithonianTriassicTuronianValanginianThis report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.Alaska Division of Geological & Geophysical SurveysMetadata Managermailing and physical

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FairbanksAK99709-3707USA(907)451-5020(907)451-5050dggspubs@alaska.gov8 am to 4:30 pm, Monday through Friday, except State holidaysPlease view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible.This work was jointly funded by the State of Alaska and the U.S. Geological Survey through the Earth Mapping Resources Initiative (Earth MRI) program through cooperative agreement G23AC00372. The geochronology data presented in this study were collected at the University of Alaska Fairbanks Geophysical Institute's Geochronology Laboratory. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the opinions or policies of the U.S. Geological Survey. Mention of trade names or commercial products does not constitute their endorsement by the U.S. Geological Survey.Buchanan, J.W.Barrera, M.L.Moshrefzadeh, J.A.Truskowski, C.M.Newberry, R.J.2025Raw Data FileRDF 2025-25Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys4 phttps://doi.org/10.14509/31731Buchanan, J.W.Gavel, M.M.Barrera, M.L.Regan, S.P.Newberry, R.J.2025Raw Data FileRDF 2025-14Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys4 phttps://doi.org/10.14509/31553Buchanan, J.W.Wypych, AlicjaBarrera, M.L.Biegel, J.M.Gavel, M.M.Harvey, D.A.Ketcham, R.A.Muller, I.P.Naibert, T.J.Newberry, R.J.Regan, S.P.Szumigala, D.J.Twelker, EvanWildland, A.D.2025Raw Data FileRDF 2024-2Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys5 phttps://doi.org/10.14509/31123Gavel, M.M.Twelker, EvanWypych, AlicjaNaibert, T.J.Newberry, R.J.Szumigala, D.J.Wildland, A.D.Barrera, M.L.Biegel, J.N.Harvey, D.A.Ketcham, R.A.Muller, I.P.Regan, S.P.2023Raw Data FileRDF 2023-27Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys3 phttps://doi.org/10.14509/31096Moshrefzadeh, J.A.Newberry, R.J.2025Raw Data FileRDF 2025-13Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys6 phttps://doi.org/10.14509/31537Moshrefzadeh, J.A.Buchanan, J.W.Naibert, T.J.Twelker, EvanNewberry, R.J.Szumigala, D.J.Barrera, M.L.Norwood, L.P.Acosta, M.D.Regan, S.P.2025Raw Data FileRDF 2025-5Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys5 phttps://doi.org/10.14509/31476Moshrefzadeh, JamshidAcosta, M.D.Barrera, M.L.Buchanan, J.W.Naibert, T.J.Newberry, R.J.Norwood, L.P.Regan, S.P.Szumigala, D.J.Twelker, Evan2025Raw Data FileRDF 2025-17Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys3 phttps://doi.org/10.14509/31692Newberry, R.J.Moshrefzadeh, J.A.2026Preliminary Interpretive ReportPIR 2026-2Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys33 phttps://doi.org/10.14509/32081Twelker, Evan2026Preliminary Interpretive ReportPIR 2026-3Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys1 phttps://doi.org/10.14509/32111This publication is a DGGS Raw Data File (RDF). Reports in the RDF series present field data and analytical results with limited or no interpretation by DGGS staff or project collaborators. The report and accompanying data have been evaluated by project staff for general readability and logical consistency but have not undergone technical peer review. Information presented in this release is subject to change.Not applicableThis data release is complete.Location data for samples were recorded in the WGS84 datum using GPS-enabled field tablets and provided here in the NAD83 datum. Sample location coordinates have a typical reported accuracy of about 10 meters. The locations of the 21 samples presented in this report are shown in figure 1.Sample collection - Fresh, unweathered rock samples were collected from surface outcrops by DGGS field geologists during geologic mapping in the Big Delta and Circle quadrangles. Location data for samples were recorded in the WGS84 datum using GPS-enabled field tablets. Samples were selected for age dating based on terrane, map unit, and the presence of viable mineral phases suitable for 40Ar/39Ar analysis. Each sample was examined as a hand specimen under a binocular microscope and as a thin section under a petrographic microscope to identify unaltered mineral phases and confirm suitability for geochronologic analysis.2023Sample analysis - Rock samples were submitted to the Geochronology Laboratory at the University of Alaska Fairbanks Geophysical Institute, where they were processed and prepared for 40Ar/39Ar analyses. The rock samples were broken up and crushed to separate individual mineral grains. The samples were then sieved and separated to sort mineral grains. Targeted grains were manually selected under a microscope for further analysis. The grains selected from each sample were irradiated at the Oregon State University nuclear research reactor along with the FC-2 Fish Canyon Tuff sanidine standard (28.201 +/- 0.046 Ma; Kuiper and others, 2008). The irradiation procedure transformed some 39K to 39Ar. The samples were then step heated with a laser to release the gases they contained. The argon gas was separated, and the main argon isotopes (36Ar, 37Ar, 38Ar, 39Ar, and 40Ar) were measured via mass spectrometer at the UAF Geochronology Laboratory. The resulting 40Ar/39Ar ratios were compared with those of the FC-2 standard to determine the ages of the unknown samples.2024point0.00000010.0000001decimal degreesNAD83GRS 806378137298.257222101RDF2026-14-ArAr_data.csv, RDF2026-14-ArAr_data_dictionary.csvAnalytical lab data and accompanying data dictionaryDGGS and UAFArAr_dataRDF2026-14-ArAr_summary-data.csv, RDF2026-14-ArAr_summary-data_dictionary.csvSummary data spreadsheet and accompanying data dictionaryDGGS and UAFArAr_summary-dataAlaska Division of Geological & Geophysical SurveysMetadata Managermailing and physical

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FairbanksAK99709-3707USA(907)451-5020(907)451-5050dggspubs@alaska.gov8 am to 4:30 pm, Monday through Friday, except State holidaysPlease view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible.RDF 2026-14The State of Alaska makes no expressed or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.DGGS publications are available as free online downloads or you may purchase paper hard-copies or digital files on CD/DVD or other digital storage media by mail, phone, fax, or email from the DGGS Fairbanks office. To purchase this or other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard. Turnaround time is 1-2 weeks unless special arrangements are made and an express fee is paid. Shipping charge will be the actual cost of postage and will be added to the total amount due. Contact us for the exact shipping amount.Contact DGGS for current pricingspreadsheet20260701tablehttps://doi.org/10.14509/32086Free download20260701Alaska Division of Geological & Geophysical SurveysSimone MontayneMetadata Managermailing and physical

3354 College Road

FairbanksAK99709-3707USA(907)451-5020(907)451-5050dggspubs@alaska.gov8 am to 4:30 pm, Monday through Friday, except State holidaysFGDC Content Standard for Digital Geospatial MetadataFGDC-STD-001-1998If the user has modified the data in any way they are obligated to describe the types of modifications they have performed in the supporting metadata file. User specifically agrees not to imply that changes they made were approved by the Alaska Department of Natural Resources or Division of Geological & Geophysical Surveys.https://dggs.alaska.gov/metadata/dggs.extdggs metadata extensions