Identification_Information: Citation: Citation_Information: Originator: Moshrefzadeh, J.A. Originator: Naibert, T.J. Originator: Hofmann, Florian Originator: Newberry, R.J. Originator: Twelker, Evan Originator: Buchanan, J.W. Publication_Date: 2026 Title: 40Ar/39Ar geochronology data from the Big Delta and Circle quadrangles, Alaska Geospatial_Data_Presentation_Form: spreadsheet Series_Information: Series_Name: Raw Data File Issue_Identification: RDF 2026-14 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 55 p. Online_Linkage: https://doi.org/10.14509/32086 Description: Abstract: 40Ar/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. Purpose: 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. Supplemental_Information: >ArAr_data: Analytical lab data and accompanying data dictionary >ArAr_summary-data: Summary data spreadsheet and accompanying data dictionary Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 2023 Ending_Date: 2026 Currentness_Reference: ground condition Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -146.452067 East_Bounding_Coordinate: -144.324495 North_Bounding_Coordinate: 65.185040 South_Bounding_Coordinate: 64.378858 Keywords: Theme: Theme_Keyword_Thesaurus: ISO 19115 Topic Category Theme_Keyword: geoscientificInformation Theme: Theme_Keyword_Thesaurus: Alaska Division of Geological & Geophysical Surveys Theme_Keyword: 40Ar/39Ar Theme_Keyword: Age Dates Theme_Keyword: Amphibolite Theme_Keyword: Analyses Theme_Keyword: Analyses and Sampling Theme_Keyword: Analytical Lab Results Theme_Keyword: Analytical Results Theme_Keyword: Ar-Ar Theme_Keyword: Bedrock Theme_Keyword: Bedrock Geology Theme_Keyword: DGGS Theme_Keyword: Exploration Theme_Keyword: Gabbro Theme_Keyword: Geochronology Theme_Keyword: Geologic Theme_Keyword: Geology Theme_Keyword: Granite Theme_Keyword: Isotopes Theme_Keyword: Mineral Development Theme_Keyword: Mineral Exploration Theme_Keyword: Mineral Resources Theme_Keyword: Minerals Theme_Keyword: Mining Theme_Keyword: Muscovite Theme_Keyword: Orthogneiss Theme_Keyword: Outcrop Theme_Keyword: Phyllite Theme_Keyword: Resources Theme_Keyword: Sample Location Theme_Keyword: Schist Theme_Keyword: Sericite Place: Place_Keyword_Thesaurus: Alaska Division of Geological & Geophysical Surveys Place_Keyword: Anderson Creek Place_Keyword: Angel Creek Place_Keyword: Beaver Creek Place_Keyword: Blackshell Creek Place_Keyword: Boulder Creek Place_Keyword: Central Creek Place_Keyword: Chena River Place_Keyword: Circle Mining District Place_Keyword: Crawford Creek Place_Keyword: Dan Creek Place_Keyword: Demar Creek Place_Keyword: Emory Creek Place_Keyword: Fairbanks Mining District Place_Keyword: Far Mountain Place_Keyword: Frozenfoot Creek Place_Keyword: Glacier Creek Place_Keyword: Globe Creek Place_Keyword: Gold Creek Place_Keyword: Goodpaster Mining District Place_Keyword: Jones Pass Place_Keyword: Lawson Creek Place_Keyword: Marten Creek Place_Keyword: Mascot Creek Place_Keyword: Mastadon Creek Place_Keyword: Munson Creek Place_Keyword: Ohio Creek Place_Keyword: Olympia Creek Place_Keyword: Ottertail Creek Place_Keyword: Pine Creek Place_Keyword: Pogo Place_Keyword: Porcupine Creek Place_Keyword: Ricks Creek Place_Keyword: Rock Creek Place_Keyword: Rosebud Creek Place_Keyword: Salmonfoot Creek Place_Keyword: Shamrock Creek Place_Keyword: Shawnee Peak Place_Keyword: Sonora Creek Place_Keyword: Stone Boy Creek Place_Keyword: Stuart Creek Place_Keyword: Wickersham Creek Place_Keyword: Wolverine Creek Temporal: Temporal_Keyword_Thesaurus: Walker, J.D., Geissman, J.W., Bowring, S.A, and Babcock, L.E., comp., 2012, Geologic Time Scale v. 4.0: Geological Society of America Temporal_Keyword: Albian Temporal_Keyword: Aptian Temporal_Keyword: Cretaceous Temporal_Keyword: Eocene Temporal_Keyword: Hauterivian Temporal_Keyword: Hettangian Temporal_Keyword: Jurassic Temporal_Keyword: Norian Temporal_Keyword: Paleocene Temporal_Keyword: Paleogene Temporal_Keyword: Tithonian Temporal_Keyword: Triassic Temporal_Keyword: Turonian Temporal_Keyword: Valanginian Access_Constraints: This 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). Use_Constraints: 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. Point_of_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: Alaska Division of Geological & Geophysical Surveys Contact_Position: Metadata Manager Contact_Address: Address_Type: mailing and physical Address: 3354 College Road City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: (907)451-5020 Contact_Facsimile_Telephone: (907)451-5050 Contact_Electronic_Mail_Address: dggspubs@alaska.gov Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays Contact_Instructions: Please 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. Data_Set_Credit: 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. Cross_Reference: Citation_Information: Originator: Buchanan, J.W. Originator: Barrera, M.L. Originator: Moshrefzadeh, J.A. Originator: Truskowski, C.M. Originator: Newberry, R.J. Publication_Date: 2025 Title: LA-ICP-MS uranium-lead zircon data from samples in the Chena and Steese project areas Series_Information: Series_Name: Raw Data File Issue_Identification: RDF 2025-25 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 4 p Online_Linkage: https://doi.org/10.14509/31731 Cross_Reference: Citation_Information: Originator: Buchanan, J.W. Originator: Gavel, M.M. Originator: Barrera, M.L. Originator: Regan, S.P. Originator: Newberry, R.J. Publication_Date: 2025 Title: LA-ICP-MS uranium lead geochronologic data of zircon from igneous and meta-igneous rocks in the Chena project area, Circle, Big Delta, and Eagle quadrangles, Alaska Series_Information: Series_Name: Raw Data File Issue_Identification: RDF 2025-14 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 4 p Online_Linkage: https://doi.org/10.14509/31553 Cross_Reference: Citation_Information: Originator: Buchanan, J.W. Originator: Wypych, Alicja Originator: Barrera, M.L. Originator: Biegel, J.M. Originator: Gavel, M.M. Originator: Harvey, D.A. Originator: Ketcham, R.A. Originator: Muller, I.P. Originator: Naibert, T.J. Originator: Newberry, R.J. Originator: Regan, S.P. Originator: Szumigala, D.J. Originator: Twelker, Evan Originator: Wildland, A.D. Publication_Date: 2025 Title: Geochemical data from samples collected in 2023 for the Chena and Mount Harper projects, Big Delta, Circle, Fairbanks, and Eagle quadrangles, Alaska Series_Information: Series_Name: Raw Data File Issue_Identification: RDF 2024-2 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 5 p Online_Linkage: https://doi.org/10.14509/31123 Cross_Reference: Citation_Information: Originator: Gavel, M.M. Originator: Twelker, Evan Originator: Wypych, Alicja Originator: Naibert, T.J. Originator: Newberry, R.J. Originator: Szumigala, D.J. Originator: Wildland, A.D. Originator: Barrera, M.L. Originator: Biegel, J.N. Originator: Harvey, D.A. Originator: Ketcham, R.A. Originator: Muller, I.P. Originator: Regan, S.P. Publication_Date: 2023 Title: Field station locations and magnetic susceptibility data for the Chena-Pogo and Mount Harper projects, Big Delta and Circle quadrangles, Alaska, collected June-September 2023 Series_Information: Series_Name: Raw Data File Issue_Identification: RDF 2023-27 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 3 p Online_Linkage: https://doi.org/10.14509/31096 Cross_Reference: Citation_Information: Originator: Moshrefzadeh, J.A. Originator: Newberry, R.J. Publication_Date: 2025 Title: Electron probe microanalyzer data collected on samples from the Chena and Steese projects, Yukon-Tanana Uplands, Alaska Series_Information: Series_Name: Raw Data File Issue_Identification: RDF 2025-13 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 6 p Online_Linkage: https://doi.org/10.14509/31537 Cross_Reference: Citation_Information: Originator: Moshrefzadeh, J.A. Originator: Buchanan, J.W. Originator: Naibert, T.J. Originator: Twelker, Evan Originator: Newberry, R.J. Originator: Szumigala, D.J. Originator: Barrera, M.L. Originator: Norwood, L.P. Originator: Acosta, M.D. Originator: Regan, S.P. Publication_Date: 2025 Title: Field station locations and magnetic susceptibility data collected in 2024 for the Chena and Steese projects, Yukon-Tanana Uplands, Alaska Series_Information: Series_Name: Raw Data File Issue_Identification: RDF 2025-5 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 5 p Online_Linkage: https://doi.org/10.14509/31476 Cross_Reference: Citation_Information: Originator: Moshrefzadeh, Jamshid Originator: Acosta, M.D. Originator: Barrera, M.L. Originator: Buchanan, J.W. Originator: Naibert, T.J. Originator: Newberry, R.J. Originator: Norwood, L.P. Originator: Regan, S.P. Originator: Szumigala, D.J. Originator: Twelker, Evan Publication_Date: 2025 Title: Geochemical data from samples collected in 2024 for the Chena and Steese projects, Big Delta, Circle, Fairbanks, and Livengood quadrangles, Alaska Series_Information: Series_Name: Raw Data File Issue_Identification: RDF 2025-17 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 3 p Online_Linkage: https://doi.org/10.14509/31692 Cross_Reference: Citation_Information: Originator: Newberry, R.J. Originator: Moshrefzadeh, J.A. Publication_Date: 2026 Title: Interior Alaska amphibolite mineral compositions: A key to distinguishing metamorphic assemblage Series_Information: Series_Name: Preliminary Interpretive Report Issue_Identification: PIR 2026-2 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 33 p Online_Linkage: https://doi.org/10.14509/32081 Cross_Reference: Citation_Information: Originator: Twelker, Evan Publication_Date: 2026 Title: Geologic investigation of the Chena-Pogo area, interior Alaska Series_Information: Series_Name: Preliminary Interpretive Report Issue_Identification: PIR 2026-3 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 1 p Online_Linkage: https://doi.org/10.14509/32111 Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: This 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. Logical_Consistency_Report: Not applicable Completeness_Report: This data release is complete. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: 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. Lineage: Process_Step: Process_Description: 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. Process_Date: 2023 Process_Step: Process_Description: Sample 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. Process_Date: 2024 Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: point Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Geographic: Latitude_Resolution: 0.0000001 Longitude_Resolution: 0.0000001 Geographic_Coordinate_Units: decimal degrees Geodetic_Model: Horizontal_Datum_Name: NAD83 Ellipsoid_Name: GRS 80 Semi-major_Axis: 6378137 Denominator_of_Flattening_Ratio: 298.257222101 Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: RDF2026-14-ArAr_data.csv, RDF2026-14-ArAr_data_dictionary.csv Entity_Type_Definition: Analytical lab data and accompanying data dictionary Entity_Type_Definition_Source: DGGS and UAF Entity_Attribute_Layer_Name: ArAr_data Detailed_Description: Entity_Type: Entity_Type_Label: RDF2026-14-ArAr_summary-data.csv, RDF2026-14-ArAr_summary-data_dictionary.csv Entity_Type_Definition: Summary data spreadsheet and accompanying data dictionary Entity_Type_Definition_Source: DGGS and UAF Entity_Attribute_Layer_Name: ArAr_summary-data Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: Alaska Division of Geological & Geophysical Surveys Contact_Position: Metadata Manager Contact_Address: Address_Type: mailing and physical Address: 3354 College Road City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: (907)451-5020 Contact_Facsimile_Telephone: (907)451-5050 Contact_Electronic_Mail_Address: dggspubs@alaska.gov Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays Contact_Instructions: Please 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. Resource_Description: RDF 2026-14 Distribution_Liability: The 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. Standard_Order_Process: Non-digital_Form: 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. Fees: Contact DGGS for current pricing Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: spreadsheet Format_Version_Date: 20260701 Format_Information_Content: table Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: https://doi.org/10.14509/32086 Fees: Free download Metadata_Reference_Information: Metadata_Date: 20260701 Metadata_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: Alaska Division of Geological & Geophysical Surveys Contact_Person: Simone Montayne Contact_Position: Metadata Manager Contact_Address: Address_Type: mailing and physical Address: 3354 College Road City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: (907)451-5020 Contact_Facsimile_Telephone: (907)451-5050 Contact_Electronic_Mail_Address: dggspubs@alaska.gov Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays Metadata_Standard_Name: FGDC Content Standard for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998 Metadata_Use_Constraints: If 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. Metadata_Extensions: Online_Linkage: https://dggs.alaska.gov/metadata/dggs.ext Profile_Name: dggs metadata extensions