Identification_Information: Citation: Citation_Information: Originator: Petersen, E.I. Originator: Fusso, L.A. Originator: Geotech Ltd. Originator: Aqua Geo Frameworks LLC Publication_Date: 2026 Title: Candle Hills airborne electromagnetic survey, Kuskokwim region, Alaska Geospatial_Data_Presentation_Form: digital, data Series_Information: Series_Name: Geophysical Report Issue_Identification: GPR 2026-3 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 9 p Online_Linkage: https://doi.org/10.14509/31963 Description: Abstract: Candle Hills airborne electromagnetic survey, Kuskokwim region, Alaska, Geophysical Report 2026-3, covers a portion of the McGrath and Iditarod quadrangles, southwest of McGrath, across part of the Kuskokwim Mountains in western interior Alaska. The McGrath and Iditarod quadrangles are prime exploration targets because they lie within historically productive mining districts and contain geologic structures and rock units known to host gold and other metallic mineral deposits (Bundtzen and Miller, 1996; Bundtzen and others, 2004; Miller and others, 2005). The survey was conducted to characterize subsurface electrical resistivity variations and to support geologic mapping and mineral resource evaluation. These data provide a framework for identifying concealed lithologic contacts, structural features, and alteration zones that may indicate areas of elevated mineral potential. Time-domain electromagnetic data were acquired using the helicopter-mounted VTEM Terrain system on August 5-12, 2025, by Geotech Ltd. A total of 1060 line-kilometers were flown over a single survey block measuring 369.5 square kilometers. The block was flown with northwest-southeast line orientation and a nominal spacing of 400 meters, along with northeast-southwest oriented tie lines with a nominal spacing of 4000 meters. Mean ground clearance was 44 meters, with a mean survey speed of 86 km/hr. Geotech Ltd. provided initial resistivity models, produced via simple inversion using a technique termed Resistivity Depth Imaging (RDI). These models are referred to in the provided data files as "geotech_rdi." Aqua Geo Frameworks then produced a spatially constrained inversion model (referred to in the data files as "agf_sci"), which incorporates both along-track and cross-track constraints. The Aqua Geo Frameworks model is recommended for end-users as it resolves finer-scale structures, including faults. We also provide a 3D voxel dataset registered to elevation rather than raw depth for the agf_sci model. These data are provided as a Geophysical Report under an open end-user license and are available on the DGGS website https://doi.org/10.14509/31963. Purpose: The purpose of the Candle Hills airborne electromagnetic survey is to characterize subsurface electrical resistivity across a portion of the McGrath and Iditarod quadrangles in western interior Alaska to support geologic mapping and mineral resource evaluation. This survey provides high‑resolution geophysical data that help identify concealed lithologic contacts, structural features, and alteration zones associated with gold and other metallic mineral deposits within the Kuskokwim Mountains. The resulting resistivity models and derived 3D datasets offer a framework for assessing mineral potential in an area of historically productive mining districts and geologically favorable host rocks. Supplemental_Information: >ascii_data: ASCII format line data, other ASCII data >databases_geosoft: Geosoft format database of final line data, other Geosoft format databases >documents: Project report, calibration reports >grids_geosoft: Oasis montaj Geosoft GRD format gridded data >grids_tif: Geographically registered data value rasters of gridded data, GeoTiff format >maps_pdf_format: Printable and geographically registered maps in pdf format. >models_resistivity: Models of subsurface resistivity inverted from measured EM response. agf_sci is the recommended model for end-users. >vector_data: Line path and survey boundary in Esri shapefile (shp) format Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 2025 Currentness_Reference: ground condition Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -156.315876 East_Bounding_Coordinate: -155.554223 North_Bounding_Coordinate: 62.953699 South_Bounding_Coordinate: 62.664598 Keywords: Theme: Theme_Keyword_Thesaurus: ISO 19115 Topic Category Theme_Keyword: geoscientificInformation Theme: Theme_Keyword_Thesaurus: Alaska Division of Geological & Geophysical Surveys Theme_Keyword: Airborne Geophysical Survey Theme_Keyword: Analytic Signal Theme_Keyword: Apparent Resistivity Contours Theme_Keyword: Apparent Resistivity Data Theme_Keyword: Apparent Resistivity Map Theme_Keyword: Apparent Resistivity Survey Theme_Keyword: Bedrock Geology Theme_Keyword: Conductivity Survey Theme_Keyword: Critical Minerals Theme_Keyword: DGGS Theme_Keyword: Earth MRI Theme_Keyword: Economic Geology Theme_Keyword: Economic Study Theme_Keyword: Electromagnetic Data Theme_Keyword: Electromagnetic Survey Theme_Keyword: Exploration Theme_Keyword: Geology Theme_Keyword: Geophysical Map Theme_Keyword: Geophysical Survey Theme_Keyword: Geophysics Theme_Keyword: Geophysics Search Tag Theme_Keyword: Gridded Data Theme_Keyword: Helicopter Survey Theme_Keyword: Inversion Theme_Keyword: Mineral Assessment Theme_Keyword: Mineral Deposit Models Theme_Keyword: Mineral Development Theme_Keyword: Mineral Exploration Theme_Keyword: Mineral Resources Theme_Keyword: Minerals Theme_Keyword: Remote Sensing Theme_Keyword: Resistivity Theme_Keyword: Resistivity Model Theme_Keyword: Resistivity Survey Place: Place_Keyword_Thesaurus: Alaska Division of Geological & Geophysical Surveys Place_Keyword: Beaver Creek Place_Keyword: Camp Creek Place_Keyword: Candle Creek Place_Keyword: Candle Hills Place_Keyword: Carl Creek Place_Keyword: Cash Creek Place_Keyword: Kuskokwim River Place_Keyword: McGrath Mining District Place_Keyword: Rex Creek Place_Keyword: Roundabout Mountain Place_Keyword: Tatalina River 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: GIS Manager Contact_Address: Address_Type: mailing and physical Address: 3354 College Rd City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: 907-451-5020 Contact_Electronic_Mail_Address: dggsgis@alaska.gov Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays Data_Set_Credit: This work was supported by State of Alaska capital improvement project funds. Doyon, Limited funded survey liness acquired over their land holdings. Cross_Reference: Citation_Information: Originator: Fusso, L.A. Originator: Petersen, E.I. Originator: Emond, A.M. Publication_Date: 2026 Title: Kuskokwim airborne magnetics and radiometric geophysical survey, McGrath, Alaska Series_Information: Series_Name: Geophysical Report Issue_Identification: GPR 2026-2 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Online_Linkage: https://doi.org/10.14509/31804 Cross_Reference: Citation_Information: Originator: Fusso, L.A. Originator: Petersen, E.I. Originator: EON Geosciences Inc. Publication_Date: 2025 Title: Kuskokwim airborne magnetic and radiometric survey, Ganes Creek, Alaska Series_Information: Series_Name: Geophysical Report Issue_Identification: GPR 2026-1 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Online_Linkage: https://doi.org/10.14509/31746 Cross_Reference: Citation_Information: Originator: Petersen, E.I. Originator: Fusso, L.A. Originator: Geotech Ltd. Originator: Aqua Geo Frameworks LLC Publication_Date: 2026 Title: Granite Mountain airborne electromagnetic survey, Kuskokwim Region, Alaska Series_Information: Series_Name: Geophysical Report Issue_Identification: GPR 2026-4 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Online_Linkage: https://doi.org/10.14509/31964 Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: Geophysical data were acquired according to the contractor, contract, and request-for-proposals specifications. For additional detail about survey parameters, see the accompanying project report available in the documents directory of this data distribution package. Logical_Consistency_Report: Data were supplied by providers in accordance with DGGS contract requirements (see accompanying project report). The originating coordinate system was retained for all publication products. Completeness_Report: The dataset provides processed geophysical and positional data for the entire survey extent. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: Station coordinates were positioned using a real-time or post-processed corrected differential GPS. Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: Not applicable Lineage: Process_Step: Process_Description: Data acquisition - Geotech Ltd. conducted the Candle Hills airborne electromagnetic survey from August 5-12, 2025, acquiring 1,060 line-kilometers of VTEM Terrain time-domain electromagnetic data over a 369.5 km2 block in the McGrath and Iditarod quadrangles of western interior Alaska. The survey, designed to map subsurface resistivity and support geologic mapping and mineral resource assessment, used northwest-southeast flight lines spaced 400 m apart with 4,000 m tie lines, maintaining an average 44 m ground clearance and 86 km/hr speed. Geotech produced initial Resistivity Depth Imaging models (geotech_rdi), after which Aqua Geo Frameworks generated a more detailed spatially constrained inversion (agf_sci) incorporating along-track and cross-track constraints. A 3D voxel dataset registered to elevation was also created for the agf_sci model to support interpretation. Process_Date: 2025 Process_Step: Process_Description: Data cataloged for archival and publication - Final data were published and archived by DGGS. Process_Date: 2026 Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: raster Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Grid_Coordinate_System: Grid_Coordinate_System_Name: Universal Transverse Mercator Universal_Transverse_Mercator: UTM_Zone_Number: 4 Transverse_Mercator: Scale_Factor_at_Central_Meridian: 0.999600 Longitude_of_Central_Meridian: -159 Latitude_of_Projection_Origin: 0 False_Easting: 500000.000000 False_Northing: 0 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Coordinate_Representation: Abscissa_Resolution: .00000001 Ordinate_Resolution: .00000001 Planar_Distance_Units: Meters Geodetic_Model: Horizontal_Datum_Name: WGS84 Ellipsoid_Name: WGS 84 Semi-major_Axis: 6378137 Denominator_of_Flattening_Ratio: 298.257223563 Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: ascii_data Entity_Type_Definition: ASCII format line data, other ASCII data Entity_Type_Definition_Source: Geotech Ltd. and Aqua Geo Frameworks LLC Entity_Attribute_Layer_Name: ascii_data Detailed_Description: Entity_Type: Entity_Type_Label: databases_geosoft Entity_Type_Definition: Geosoft format database of final line data, other Geosoft format databases Entity_Type_Definition_Source: Geotech Ltd. and Aqua Geo Frameworks LLC Entity_Attribute_Layer_Name: databases_geosoft Detailed_Description: Entity_Type: Entity_Type_Label: documents Entity_Type_Definition: Project report, calibration reports Entity_Type_Definition_Source: Geotech Ltd. and Aqua Geo Frameworks LLC and Alaska Division of Geological & Geophysical Surveys (DGGS) Entity_Attribute_Layer_Name: documents Detailed_Description: Entity_Type: Entity_Type_Label: grids_geosoft Entity_Type_Definition: Oasis montaj Geosoft GRD format gridded data Entity_Type_Definition_Source: Geotech Ltd. and Aqua Geo Frameworks LLC and Alaska Division of Geological & Geophysical Surveys (DGGS) Entity_Attribute_Layer_Name: grids_geosoft Detailed_Description: Entity_Type: Entity_Type_Label: grids_tif Entity_Type_Definition: Geographically registered data value rasters of gridded data, GeoTiff format Entity_Type_Definition_Source: Alaska Division of Geological & Geophysical Surveys (DGGS) Entity_Attribute_Layer_Name: grids_tif Detailed_Description: Entity_Type: Entity_Type_Label: maps_pdf_format Entity_Type_Definition: Printable and geographically registered maps in pdf format. Entity_Type_Definition_Source: Geotech Ltd. and Aqua Geo Frameworks LLC Entity_Attribute_Layer_Name: maps_pdf_format Detailed_Description: Entity_Type: Entity_Type_Label: models_resistivity Entity_Type_Definition: Models of subsurface resistivity inverted from measured EM response. agf_sci is the recommended model for end-users. Entity_Type_Definition_Source: Geotech Ltd. and Aqua Geo Frameworks LLC Entity_Attribute_Layer_Name: models_resistivity Detailed_Description: Entity_Type: Entity_Type_Label: vector_data Entity_Type_Definition: Line path and survey boundary in Esri shapefile (shp) format Entity_Type_Definition_Source: Alaska Division of Geological & Geophysical Surveys (DGGS) Entity_Attribute_Layer_Name: vector_data Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys 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 (http://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: GPR 2026-3 Distribution_Liability: The State of Alaska makes no express or implied warranties (including warranties of merchantability and fitness) with respect to the character, function, or capabilities of the electronic services 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, any failure thereof, or otherwise, and 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: see http://dx.doi.org/10.14509/31963 Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: GeoTiff, ESRI shapefile, Geosoft binary grid (GRD), Microsoft Office documents, PDF (with or without georeferencing), ER Mapper ERS, ASCII text files (including CSV), Geosoft database, AutoCAD DXF, Geosoft plot file (PLT), digital images (multiple formats), georeferenced photos (multiple formats), Geosoft ASCII XYZ, Geosoft ASCII files (PLY, i0, EXP), and KMZ. Format_Version_Date: 20260212 Format_Information_Content: Airborne electromagnetic geophysical survey data compilation Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: http://dx.doi.org/10.14509/31963 Fees: Free download Metadata_Reference_Information: Metadata_Date: 20260212 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Simone Montayne 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 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 this metadata file in any way, the user is obligated to describe the types of modifications the user has made. User specifically agrees not to misrepresent this metadata file, 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. Metadata_Extensions: Online_Linkage: http://www.dggs.alaska.gov/metadata/dggs.ext Profile_Name: dggs metadata extensions