Bedrock geologic map of the Delta mineral belt, Tok mining district, Alaska

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Frequently anticipated questions:


What does this data set describe?

Title:
Bedrock geologic map of the Delta mineral belt, Tok mining district, Alaska
Abstract:
Bedrock geologic map of the Delta mineral belt, Tok mining district, Alaska, Professional Report 122, presents the first published, field scale map that shows the metamorphic rock units and mineralization of the Delta mineral belt, integrating decades of exploration data and new geologic interpretation. It incorporates extensive but previously unpublished reconnaissance mapping completed in the 1970s by RAA, Anaconda, and ACNC, including the 1:30,000 scale traverse maps that documented metamorphic lithologies before later protolith focused mapping obscured those details. Earlier regional syntheses, such as the 1982 protolith based map by Duke and Nauman and the 1985 metamorphic and tectonic framework by Duke, provided important foundations but lacked the petrographic and geochemical constraints needed for reliable correlation. Through new mapping, lithochemistry, geophysics, drilling, and radiometric dating, this report revises stratigraphic order, unit ages, contacts, and deposit relationships, producing a modern 1:63,360 scale geologic map that clarifies the distribution and setting of massive sulfide mineralization in the eastern Alaska Range. 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/10.14509/2923.
Supplemental_Information:
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/10.14509/30584
  1. How might this data set be cited?
    Dashevsky, S.S., Schaefer, C.F., and Hunter, E.N., 2003, Bedrock geologic map of the Delta mineral belt, Tok mining district, Alaska: Professional Report PR 122, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 122 p., 2 sheets, scale 1:63,360
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -144.503735
    East_Bounding_Coordinate: -143.748085
    North_Bounding_Coordinate: 63.393036
    South_Bounding_Coordinate: 63.096723
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 1994
    Ending_Date: 2026
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: geodatabase
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a vector data set.
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 6
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -147
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000.000000
      False_Northing: 0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest .00000001
      Ordinates (y-coordinates) are specified to the nearest .00000001
      Planar coordinates are specified in Meters
      The horizontal datum used is NAD27.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.4.
      The flattening of the ellipsoid used is 1/294.9786982.
  7. How does the data set describe geographic features?
    delta_mineral_belt_ak_gems_db
    Geodatabase, layer files, style files, and fonts (Source: DGGS)
    delta_mineral_belt_gems_db
    Geodatabase, layer files, style files, and fonts (Source: DGGS)
    delta_mineral_belt_gems_geopackage
    SQLite Database file (Source: DGGS)
    delta_mineral_belt_gems_shapefile
    Shapefiles and open data files (Source: DGGS)

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
  2. Who also contributed to the data set?
    The data in this report were generated through exploration work funded by American Copper and Nickel Company, with fieldwork carried out over five seasons by the authors and ACNC teams, building on earlier unpublished mapping by Resource Associates of Alaska and partner companies. Key ACNC contributors included Edward Hunter, Sam Dashevsky, Carl Schaefer, Katherine Bull, Noelle Shriver, Roderick MacInnes, and William Shalosky, with essential support from helicopter pilots Owen Jones and Walter Greaves and mountaineer-engineer Meine Huser. Additional expertise in lithochemical interpretation and geophysics was provided by David Burrows, Edward Pattisson, Bob Lo, and Pat McGowan, while Phil Rush guided the overall exploration strategy. Publication of these results was made possible through the cooperation of Grayd Resource Corporation and the Alaska Division of Geological and Geophysical Surveys, with further improvements from reviewers Rainer Newberry, Laurel Burns, Ellen Daley, Cynthia Dusel-Bacon, Karen Clautice, and Barry Hoffman. Kinney Engineering, LLC staff used scanned and georeferenced paper maps to digitize geologic features into an AK GeMS database. Chris Wyatt conducted quality control of this digitizing work and completed the creation of the AK GeMS database. Ally M. Steinleitner implemented final database quality control and packaging. This geologic map (or report or conversion or product, etc.) was funded by the USGS National Cooperative Geologic Mapping Program under STATEMAP award number G24AC00521, 2024, and the State of Alaska General Fund. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government.
  3. To whom should users address questions about the data?
    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK
    USA

    (907)451-5020 (voice)
    (907)451-5050 (FAX)
    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.

Why was the data set created?

This geologic map provides updated bedrock geologic mapping of Alaska's Yukon-Tanana Upland regaion 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.

How was the data set created?

  1. From what previous works were the data drawn?
    Ekberg, P.G. and others, 2021 (source 1 of 3)
    Ekberg, P.G., Hendricks, M.D., and Athey, J.E., 2021, AK GeMS symbology: A description of the AK GeMS style file: Miscellaneous Publication MP 169, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 7 p
    Type_of_Source_Media: paper
    Source_Contribution: GIS analysis and digital cartography
    Hendricks, M.D. and others, 2021 (source 2 of 3)
    Hendricks, M.D., Ekberg, P.G., Athey, J.E., Wyatt, W.C., Willingham, A.L., and Naibert, T.J., 2021, AK GeMS data dictionary: A description of the Alaska geologic mapping schema: Miscellaneous Publication MP 170, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 10 p
    Type_of_Source_Media: paper
    Source_Contribution: GIS analysis and digital cartography
    U.S. Geological Survey National Cooperative Geologic Mapping Program, 2020 (source 3 of 3)
    U.S. Geological Survey National Cooperative Geologic Mapping Program, 2020, GeMS (Geologic Map Schema) - A standard format for the digital publication of geologic maps: Techniques and Methods TM 11-B10, U.S. Geological Survey, United States.

    Online Links:

    Other_Citation_Details: 1 p
    Type_of_Source_Media: paper
    Source_Contribution: GIS analysis and digital cartography
  2. How were the data generated, processed, and modified?
    Date: 2026 (process 1 of 2)
    Geologic 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).
    Date: 2026 (process 2 of 2)
    Data 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.
  3. What similar or related data should the user be aware of?
    Schaefer, C.F., and Dashevsky, S.S., 2001, Whole-rock major oxide and trace element analyses for rock samples from the Delta Mineral Belt, Tok mining district, Alaska: Raw Data File RDF 2001-2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 3 p., 1 sheet, scale 1:63,360, 1 DVD

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    Attribute 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.
  2. How accurate are the geographic locations?
    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.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This publication is a DGGS Professional Report (PR). PRs present synthesized, broad-scale, high-level scientific interpretations that integrate extensive geological mapping and analytical research, often reflecting work conducted over many years. They undergo rigorous peer review and revision.
  5. How consistent are the relationships among the observations, including topology?
    All polygon features were topologically validated according to the AK GeMS geologic mapping schema specifications.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
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.
  1. Who distributes the data set? (Distributor 1 of 1)
    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK
    USA

    (907)451-5020 (voice)
    (907)451-5050 (FAX)
    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.
  2. What's the catalog number I need to order this data set? PR 122
  3. What legal disclaimers am I supposed to read?
    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.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 03-Aug-2026
Metadata author:
Alaska Division of Geological & Geophysical Surveys
Attn: Simone Montayne
Metadata Manager
3354 College Road
Fairbanks, AK
USA

(907)451-5020 (voice)
(907)451-5050 (FAX)
dggspubs@alaska.gov
Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.9.50 on Mon Aug 03 13:49:02 2026