Geologic investigation of the Chena-Pogo area, interior Alaska

Twelker, Evan2026Geologic investigation of the Chena-Pogo area, interior AlaskageodatabasePreliminary Interpretive ReportPIR 2026-3Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys1 p.https://doi.org/10.14509/32111Geologic investigation of the Chena-Pogo area, interior Alaska, Preliminary Interpretive Report 2026-3, updates the bedrock geologic mapping of a 14,530-sq-km (5,610-sq-mi) area in the Yukon-Tanana Upland (YTU) of eastern Interior Alaska. The goals of the project are to better understand the geologic framework of known mineralization, to support the exploration and discovery of new mineral resources in the area, and to build scientific understanding of the geology of the YTU, one of Alaska's most active and important mineral belts. The project area has been a focus of gold exploration for several decades but also has additional significance for its potential to host critical minerals such as antimony, bismuth, tellurium, and tungsten. Project work was completed by Alaska Division of Geological & Geophysical Surveys (DGGS) staff and collaborators during 2023, 2024, and 2025 field seasons and draws on additional published and unpublished work completed during prior years by DGGS, University of Alaska, and U.S. Geological Survey staff. The dataset provides geologic, structural, stratigraphic, and geochronologic information organized according to the GeMS and AK GeMS mapping schemas. The complete report, geodatabase, and ESRI fonts and style files are available from the Alaska Division of Geological & Geophysical Surveys website: http://doi.org/10.14509/32111.This geologic map provides updated bedrock geologic mapping of Alaska's Yukon-Tanana Upland to support mineral-resource evaluation, improve understanding of the region's geologic framework, and inform studies of both known mineralization and critical-mineral potential. The resulting geologic information supports responsible resource development, guides land-management decisions, and strengthens the State of Alaska's understanding of its mineral-resource base.This geodatabase is organized according to the AK GeMS mapping schema Hendricks, M.D., Macpherson, A.E., Athey, J.E., Wyatt, W.C., Montayne, Simone, Buchanan, Wes, Rivera, P.G., and Steinleitner, A.M., 2024, AK GeMS data dictionary: A description of the Alaska geologic mapping schema: Alaska Division of Geological & Geophysical Surveys Miscellaneous Publication 170 v. 2, 13 p. https://doi.org/10.14509/31172. The distribution package includes ESRI fonts and style files, along with usage instructions. Further documentation of the symbology is provided by Ekberg, P.G., Hendricks, M.D., and Athey, J.E., 2021, AK GeMS symbology: A description of the AK GeMS style file: Alaska Division of Geological & Geophysical Surveys Miscellaneous Publication 169, 7 p. https://doi.org/10.14509/3058420232026ground conditionCompleteNone planned-147.521933-143.68008265.41587464.228578ISO 19115 Topic CategorygeoscientificInformationAlaska Division of Geological & Geophysical SurveysAllochthonAmphiboliteAndesiteArgilliteBasaltBatholithBedrockCarbonatesConglomerateCorrelationDGGSDikeDioriteDolomiteDolostoneDuniteEarth MRIExhumationExplorationFaultsFossilsGabbroGarnetGeMS DB L3 CompliantGeMS DB v2GeodatabaseGeologicGeologic MapGeological ProcessGeologyGneissGraniteGranodioriteGraphiteGraywackeGreenschistGreenstoneHadrosaurHornfelsIgneousIgneous RocksInterpretationIntrusiveJadeLithologyMagnetic DataMagnetic SusceptibilityMarbleMetagenesisMetaigneous UnitsMetalsMetamorphicMetamorphic DepositsMetamorphic GradeMetamorphic MineralsMetamorphic RocksMetamorphismMetasedimentary RocksMetavolcanic rocksMetavolcanicsMineral AssessmentMineral DepositsMineral DevelopmentMineral ExplorationMineral ResourcesMineralogyMineralsMiningMonaziteMonzodioriteMonzograniteMonzoniteOrthogneissOutcropPegmatitePetrogenesisPetrographicPetrographyPetrologyPhyllitePlagioclasePlutonicPlutonic ComplexPlutonic HostedPlutonic RocksPlutonsPorphyryQuartziteRare Earth ElementsRegionalRegional MetamorphismResource AssessmentResource EvaluationResourcesRhyoliteRock PropertiesRock UnitsRocksSandstoneSchistSedimentSedimentarySedimentary RocksSerpentiniteShaleSillimaniteSkarnSlateStrategic and Critical Minerals Assessment ProjectStrategic MineralsStratigraphyStructural GeologyTalcTectonicsTerranesTonaliteUltramaficUltramafic RocksUndifferentiated BedrockVolcanicVolcanic RocksVolcaniclasticAlaska Division of Geological & Geophysical SurveysAcme CreekAlaskaAnderson CreekAngel CreekAntimony CreekAnvil CreekBathing Beauty PondBear CreekBear LakeBeaver CreekBirch CreekBlack Bear CreekBlack MountainBlackshell CreekBlair LakesBluestone CreekBonanza CreekBonnifield Mining DistrictBoulder CreekBuckley Bar CreekBullfrog CreekButte CreekCalifornia CreekCamp CreekCaribou CreekCash CreekCentral CreekChena Hot SpringsChena LakeChena RiverCircle Mining DistrictClear CreekClums Fork Birch CreekColorado CreekCottonwood CreekCrawford CreekDan CreekDeep CreekDemar CreekDenver CreekDexter CreekDivide CreekDry CreekEldorado CreekEmory CreekFairbanks Mining DistrictFar MountainFlag HillFlat CreekFlume CreekFourmile CreekFrench CreekGlacier CreekGlobe CreekGold CreekGoodpaster Mining DistrictGoodpaster RiverGoose CreekGranite CreekGranite TorsGrayling LakeGraystone CreekGreat Unknown CreekGrizzly Bear MineGrizzly CreekGulch CreekHarding LakeHarrison CreekHartman LakeHidden LakeHorner CreekHorse CreekHorseshoe LakeHunts CreekIndian CreekJohnson CreekJones PassKing CreekLast Chance CreekLawson CreekLenant CreekLohi CreekLost CreekLyrad CreekMaiden CreekMalburn CreekManchu LakeMarshall MountainMarten CreekMascot CreekMastadon CreekMontana CreekMonument CreekMoose CreekMoose LakeMosquito CreekMunson CreekNinetyeight CreekNo Grub CreekNorth PoleNugget CreekOhio CreekOlympia CreekOttertail CreekPaldo CreekPalmer CreekPasco CreekPine CreekPleasant CreekPleasant ValleyPolaris LakePorcupine CreekPortage CreekQuartz CreekRedmond CreekRichardson Mining DistrictRicks CreekRock CreekSalcha RiverSalmonfoot CreekSerpentine CreekSevenmile CreekSeventymileShamrock CreekShaw CreekShawnee PeakSheep CreekSlate CreekSonora CreekStiles CreekStone Boy CreekStone Boys Tent CreekStringer Road PondStuart CreekSullivan CreekSummit CreekTanana RiverTeuchet CreekThomas CreekTibbs CreekVolcano CreekWheeler CreekWhite CreekWickersham CreekWilliams CreekWillow CreekWolf CreekWolverine CreekAlaska Division of Geological & Geophysical SurveysFairbanks SchistFairbanks-Chena AssemblageLake George AssemblageSeventymile TerraneYukon-Tanana TerraneYukon-Tanana UplandWalker, J.D., Geissman, J.W., Bowring, S.A, and Babcock, L.E., comp., 2012, Geologic Time Scale v. 4.0: Geological Society of AmericaDevonianLate CretaceousLate DevonianMississippianPaleocenePaleozoicPrecambrianProterozoicTriassicThis 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

3354 College Road

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.We thank the many individuals and organizations who contributed to this project. Northern Star Resources Ltd. geologists shared valuable knowledge, maps, and samples from the Pogo Mine area, and Resolution Minerals Ltd., Millrock Resources Inc., and Christine Lawley provided prior mapping and geophysical models that aided interpretation. We appreciate insights from Peter Franz (Metallogeny Inc.) and cooperation from Tectonic Metals Inc. in the Tibbs and Paldo Creek areas. U.S. Geological Survey collaborators offered helpful discussions, and Jacob Murchek supplied a merged aeromagnetic grid used during fieldwork. The Arizona LaserChron Center, the University of Alaska Advanced Instrumentation Laboratory, and the University of Alaska Geochronology facility supported geochronologic and mineral-chemical analyses. We thank the U.S. Bureau of Land Management Eastern Interior Field Office and Alaska State Parks for assistance with permitting and access. Chena Hot Springs Resort provided an excellent field base, and we are especially grateful to Keith Warren and Aurora Aviation Services for safe and reliable air support. This project was funded by State of Alaska capital funds and the U.S. Geological Survey Earth MRI program (cooperative agreement G23AC00372). The views expressed are those of the authors and do not represent U.S. Geological Survey policy; trade names are used for descriptive purposes only and do not imply endorsement.Emond, A.M.MPX Geophysics LTD2022Tanana River and Big Delta airborne magnetic and radiometric surveyGeophysical ReportGPR 2022-1Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys4 phttps://doi.org/10.14509/30899Gavel, M.M.Regan, S.P.Holland, MarkWildland, A.D.Wypych, AlicjaNaibert, T.J.Twelker, Evan2023U-Pb zircon geochronology of bedrock samples collected in the Eagle and Tanacross quadrangles, eastern AlaskaPreliminary Interpretive ReportPIR 2023-2Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys38 phttps://doi.org/10.14509/31013Gavel, M.M.Wypych, AlicjaNaibert, T.J.Twelker, EvanNewberry, R.J.Barrera, M.L.Szumigala, D.J.Truskowski, C.M.Muller, I.P.Fessenden, S.N.Blackwell, N.J.Harvey, D.A.Wildland, A.D.2025Bedrock geologic map of the Mount Harper-Middle Fork area, Eagle Quadrangle, AlaskaPreliminary Interpretive ReportPIR 2025-2DFairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys1 sheet, scale 1:100,000https://doi.org/10.14509/31652Hendricks, M.D.Macpherson, A.E.Athey, J.E.Wyatt, W.C.Montayne, SimoneBuchanan, J.W.Rivera, P.G.Steinleitner, A.M.2024AK GeMS data dictionary: A description of the Alaska geologic mapping schemaMiscellaneous PublicationMP 170 v. 2Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys13 phttps://doi.org/10.14509/31172Moshrefzadeh, 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, Evan2025Geochemical data from samples collected in 2024 for the Chena and Steese projects, Big Delta, Circle, Fairbanks, and Livengood quadrangles, AlaskaRaw Data FileRDF 2025-17Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys3 phttps://doi.org/10.14509/31692Moshrefzadeh, J.A.Naibert, T.J.Hofmann, FlorianNewberry, R.J.Twelker, EvanBuchanan, J.W.202640Ar/39Ar geochronology data from the Big Delta and Circle quadrangles, AlaskaRaw Data FileRDF 2026-14Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys55 phttps://doi.org/10.14509/32086Naibert, T.J.Benowitz, J.A.Wypych, AlicjaSicard, K.R.Twelker, Evan202040Ar/39Ar data from the Tanacross D-1 and parts of the D-2, C-1, and C-2 quadrangles, AlaskaRaw Data FileRDF 2020-12Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys35 phttps://doi.org/10.14509/30466Naibert, T.J.Wypych, AlicjaNewberry, R.J.Twelker, EvanGavel, M.M.Wildland, A.D.Barrera, M.L.Szumigala, D.J.Regan, S.P.Avirett, D.F.Bernard, C.M.Blackwell, N.J.Fessenden, S.N.Harvey, D.A.Hubbard, A.K.Masterman, S.S.Muller, I.P.Turner, M.M.Wyatt, W.C.2024Geologic background and map unit descriptions to accompany bedrock geologic maps of the western Tanacross and Taylor Mountain areas, Tanacross and Eagle quadrangles, AlaskaPreliminary Interpretive ReportPIR 2024-6AFairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys39 phttps://doi.org/10.14509/31167Newberry, R.J.Bundtzen, T.K.Clautice, K.H.Combellick, R.A.Douglas, TomLaird, G.M.Liss, S.A.Pinney, D.S.Reifenstuhl, R.R.Solie, D.N.1996Preliminary geologic map of the Fairbanks mining district, AlaskaPublic Data FilePDF 96-16Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys17 p., 2 sheets, scale 1:63,360https://doi.org/10.14509/1740Newberry, R.J.Twelker, Evan2021Metamorphism of the Ladue River-Mount Fairplay areaReport of InvestigationRI 2021-5BFairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveysp. 33-39https://doi.org/10.14509/30736Newberry, R.J.Moshrefzadeh, J.A.2026Interior Alaska amphibolite mineral compositions: A key to distinguishing metamorphic assemblagePreliminary Interpretive ReportPIR 2026-2Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys33 phttps://doi.org/10.14509/32081Smith, T.E.Pessel, G.H.Wiltse, M.A.1987Mineral assessment of the Lime Peak-Mt. Prindle area, AlaskaMiscellaneous PublicationMP 29Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys712 p., 13 sheets, scale 1:63,360https://doi.org/10.14509/731Solie, D.N.Werdon, M.B.Freeman, L.K.Newberry, R.J.Szumigala, D.J.Speeter, G.G.Elliott, B.A.2019Bedrock-geologic map, Alaska Highway corridor, Tetlin Junction, Alaska to Canada borderPreliminary Interpretive ReportPIR 2019-3Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys16 p., 2 sheets, scale 1:63,360https://doi.org/10.14509/30038Twelker, EvanNewberry, R.J.Naibert, T.J.Wypych, AlicjaGavel, M.M.Barrera, M.L.Szumigala, D.J.Truskowski, C.M.Muller, I.P.Fessenden, S.N.Blackwell, N.J.Harvey, D.A.Wildland, A.D.2025Bedrock geologic maps of the Mount Harper-Middle Fork area, Volkmar River-Healy River area, Goodpaster River-Shaw Creek area, and the Richardson Mining District, AlaskaPreliminary Interpretive ReportPIR 2025-2Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys38 phttps://doi.org/10.14509/31648Twelker, EvanNewberry, R.J.Wypych, AlicjaNaibert, T.J.Wildland, A.D.Sicard, K.R.Regan, S.P.Athey, J.E.Wyatt, W.C.Lopez, J.A.2021Bedrock geologic map of the Ladue River-Mount Fairplay area, Tanacross and Nabesna quadrangles, AlaskaReport of InvestigationRI 2021-5AFairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveysp. 1-32, 1 sheet, scale 1:100,000https://doi.org/10.14509/30735Werdon, M.B.Athey, J.E.Szumigala, D.J.Newberry, R.J.Grady, J.C.Munly, W.C.2001Major-oxide, minor-oxide, trace-element, and geochemical data from rocks collected in the Salcha River-Pogo area in 2000, Big Delta and northwestern Eagle quadrangles, AlaskaRaw Data FileRDF 2001-1Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys19 p., 1 sheet, scale 1:250,000https://doi.org/10.14509/2661Werdon, M.B.Newberry, R.J.Athey, J.E.Szumigala, D.J.2004Bedrock geologic map of the Salcha River-Pogo area, Big Delta Quadrangle, AlaskaReport of InvestigationRI 2004-1BFairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys19 p., 1 sheet, scale 1:63,360https://doi.org/10.14509/3209Werdon, M.B.Newberry, R.J.Athey, J.E.Szumigala, D.J.Freeman, L.K.Lessard, R.R.Hendry, K.R.Wiltse, M.A.2003Major-oxide, minor-oxide, trace-element, and geochemical data from rocks collected in the Big Delta Quadrangle, Alaska in 2002Raw Data FileRDF 2003-2Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys45 phttps://doi.org/10.14509/2997Wiltse, M.A.Reger, R.D.Newberry, R.J.Pessel, G.H.Pinney, D.S.Robinson, M.S.Solie, D.N.1995Bedrock geologic map of the Circle mining district, AlaskaReport of InvestigationRI 95-2BFairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys1 sheet, scale 1:63,360https://doi.org/10.14509/2515Wypych, AlicjaHubbard, T.D.Naibert, T.J.Athey, J.E.Newberry, R.J.Sicard, K.R.Twelker, EvanWerdon, M.B.Willingham, A.L.Wyatt, W.C.Lockett, A.C.2021Northeast Tanacross geologic map and map units and descriptionsReport of InvestigationRI 2020-9BFairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveysp. 9-26, 1 sheet, scale 1:63,360https://doi.org/10.14509/30539Wypych, AlicjaJones, J.V., IIIO'Sullivan, Paul2020U-Pb Zircon ages from bedrock samples collected in the Tanacross D-1, and parts of the D-2, C-1, and C-2 quadrangles, AlaskaPreliminary Interpretive ReportPIR 2020-2Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys19 phttps://doi.org/10.14509/30465Attribute fields within each feature class are populated using the map symbology and corresponding applicable values from the GeMS and AK GeMS specifications. When known, certainty in attribute interpretation is indicated in the relevant fields. Attribute accuracy varies throughout the map and is scale-dependent.All polygon features were topologically validated according to the AK GeMS geologic mapping schema specifications.This publication is a DGGS Preliminary Interpretive Report (PIR). PIRs present emergent interpretations of geologic mapping or analytical investigation. These publications are reviewed for clarity and consistency and receive limited peer review.Certainty in feature boundaries or location varies throughout the map. Data fields within each feature class and the accompanying orientation and location confidence lookup tables record the authors' degree of confidence in the location of applicable features.Ekberg, P.G.Hendricks, M.D.Athey, J.E.2021AK GeMS symbology: A description of the AK GeMS style fileMiscellaneous PublicationMP 169Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys7 phttps://doi.org/10.14509/30584paper2021publication dateEkberg, P.G. and others, 2021GIS analysis and digital cartographyHendricks, M.D.Ekberg, P.G.Athey, J.E.Wyatt, W.C.Willingham, A.L.Naibert, T.J.2021AK GeMS data dictionary: A description of the Alaska geologic mapping schemaMiscellaneous PublicationMP 170Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys10 phttps://doi.org/10.14509/30669paper2021publication dateHendricks, M.D. and others, 2021GIS analysis and digital cartographyU.S. Geological Survey National Cooperative Geologic Mapping Program2020GeMS (Geologic Map Schema) - A standard format for the digital publication of geologic mapsTechniques and MethodsTM 11-B10United StatesU.S. Geological Survey1 phttps://dggs.alaska.gov/pubs/id/30585paper2020publication dateU.S. Geological Survey National Cooperative Geologic Mapping Program, 2020GIS analysis and digital cartographyGeologic mapping - DGGS Mineral Resources Section staff conducted bedrock geologic mapping across the 14,530-sq-km Chena-Pogo project area during the 2023-2025 field seasons. During fieldwork, crews collected 4,800 bedrock observation stations, 429 geochemical samples, and 51 geochronology samples, and measured magnetic-susceptibility values to support map-unit characterization. In addition, previously published DGGS and USGS maps covering portions of the project area were compiled and modified by correlating original map units to those used in this publication, removing surficial deposits where present, simplifying geologic detail for display at 1:100,000 scale, and updating interpretations based on new field and analytical data. To organize the final mapping, the project was divided into four 1:100,000-scale map sheets (NW Chena, NE Chena, SW Chena, and SE Chena). Across these sheets, map units were standardized and described in the accompanying report. For GIS distribution, the four maps were combined into a single geologic map database formatted in both the Geologic Mapping Schema (GeMS) and the Alaska Geologic Mapping Schema (AK GeMS).2026Data packaging - DGGS organized and attributed the geologic and geographic features according to the AK GeMS schema, then programmatically transformed the data into four distribution formats: (1) an AK GeMS data package containing the full database and supporting files, (2) a GeMS data package converted to the USGS base standard, (3) a SQLite database file, and (4) a simplified shapefile package with shapefile representations of the data.2026vectorUniversal Transverse Mercator60.999600-1470500000.0000000coordinate pair.00000001.00000001MetersWGS84WGS 846378137298.257223563chena_pogo_ak_gems_dbGeodatabase, layer files, style files, and fontsDGGSchena_pogo_ak_gems_dbchena_pogo_gems_dbGeodatabase, layer files, style files, and fontsDGGSchena_pogo_gems_dbchena_pogo_gems_geopackageSQLite Database fileDGGSchena_pogo_gems_geopackagechena_pogo_gems_shapefileShapefiles and open data filesDGGSchena_pogo_gems_shapefileAlaska Division of Geological & Geophysical SurveysMetadata 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