Electron probe microanalyzer data collected on samples from the Chena and Steese projects, Yukon-Tanana Uplands, Alaska

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Frequently anticipated questions:


What does this data set describe?

Title:
Electron probe microanalyzer data collected on samples from the Chena and Steese projects, Yukon-Tanana Uplands, Alaska
Abstract:
Electron probe microanalyzer data collected on samples from the Chena and Steese projects, Yukon-Tanana Uplands, Alaska, Raw Data File 2025-13, provides electron probe microanalyzer (EPMA) geochemical data for individual mineral phases targeted in selected rock samples collected during the 2024 field season, along with one sample each from the 2023 and 1995 field seasons. EPMA is an analytical technique in which X-rays are excited by an electron beam. When introduced to an electron beam, each element produces X-rays with characteristic wavelengths. Therefore, EPMA allows for non-destructive quantitative analysis by comparing wavelength intensities of samples to those emitted from standards of known composition. The elements analyzed are presented as weight percent (wt.%) oxide (for most samples Na2O, MgO, Al2O3, SiO2, K2O, TiO2, CaO, FeO, and MnO; for ultramafic samples Cr2O3 instead of TiO2 and NiO instead of K2O). We do not report concentrations for elements present below detection limits-for example, TiO2, MgO, and MnO in plagioclase. The lithologies selected for electron microprobe analyses presented in this report include ultramafic, amphibolite, eclogite, schist, syenite, and paragneiss. The mineral phases analyzed from these samples include feldspar, amphibole, pyroxene, olivine, spinel, mica, garnet, epidote, chlorite, ilmenite, rutile, tourmaline, serpentine, and aluminosilicates. These data and report are available from the DGGS website: http://doi.org/10.14509/31537.
Supplemental_Information:
data:    Analytical lab data and accompanying data dictionary	
sample-summary:    Summary data spreadsheet and accompanying data dictionary
  1. How might this data set be cited?
    Moshrefzadeh, J.A., and Newberry, R.J., 2025, Electron probe microanalyzer data collected on samples from the Chena and Steese projects, Yukon-Tanana Uplands, Alaska: Raw Data File RDF 2025-13, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 6 p.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -147.658324
    East_Bounding_Coordinate: -143.842385
    North_Bounding_Coordinate: 65.484846
    South_Bounding_Coordinate: 64.361696
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 2023
    Ending_Date: 2025
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: spreadsheet
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a point data set.
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.0000001. Longitudes are given to the nearest 0.0000001. Latitude and longitude values are specified in decimal degrees. The horizontal datum used is NAD83.
      The ellipsoid used is GRS 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222101.
  7. How does the data set describe geographic features?
    rdf2025_013_EPMA_data.csv, rdf2025_013_EPMA_data_dictionary.csv
    Analytical lab data and accompanying data dictionary (Source: DGGS)
    rdf2025_013_EPMA_sample_summary.csv, rdf2025_013_EPMA_sample_summary_data_dictionary.csv
    Summary data spreadsheet and accompanying data dictionary (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?
    We thank Nathan Graham for his assistance at the University of Alaska Fairbanks Advanced Instrumentation Laboratory. The DGGS Chena and Steese projects are funded by the State of Alaska and the U.S. Geological Survey's (USGS) Earth Mapping Resources Initiative (Earth MRI) program under Cooperative Agreement numbers G24AC00323 and G23AC00372. 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 USGS. Mention of trade names or commercial products does not constitute their endorsement by the USGS.
  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?

To advance geological research in interior Alaska, we conducted electron probe microanalyzer (EPMA) analyses to obtain detailed geochemical data from individual mineral phases within selected rock samples. These data supported five principal objectives: (1) characterizing ultramafic rocks from the Seventymile Terrane and comparing them with lithologies of uncertain origin in adjacent Earth MRI areas; (2) clarifying the metamorphic identity of eclogitic and amphibolite-like rocks within the Chatanika assemblage; (3) analyzing mineral compositions to distinguish among diverse amphibolite units; (4) estimating pressure-temperature conditions to evaluate contrasts between assemblages; and (5) resolving ambiguities surrounding mafic phases associated with the Roy Creek intrusion. Collectively, this work contributes to a broader understanding of lithologic variability, metamorphic evolution, and geochemical diversity across the Yukon-Tanana Uplands.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 2024 (process 1 of 2)
    Sample collection - DGGS geologists collected rock samples furing the 2024 field season while conducting 1:100,000-scale bedrock geologic mapping of a 9,635 km2 (~3,720 mi2) area of the Yukon-Tanana Uplands of eastern Interior Alaska
    Date: 2025 (process 2 of 2)
    Analytical methods - DGGS staff used an electron probe microanalyzer (EPMA) to analyze individual mineral phases in selected rock samples from the 2024 field season, along with one sample each from 2023 and 1995. Their selections for electron microprobe analysis included ultramafic, amphibolite, eclogite, schist, syenite, and paragneiss lithologies. They targeted mineral phases such as feldspar, amphibole, pyroxene, olivine, spinel, mica, garnet, epidote, chlorite, ilmenite, rutile, tourmaline, serpentine, and aluminosilicates. They reported elemental concentrations as weight percent oxides-typically Na2O, MgO, Al2O3, SiO2, K2O, TiO2, CaO, FeO, and MnO, with Cr2O3 and NiO replacing TiO2 and K2O in ultramafic samples.
  3. What similar or related data should the user be aware of?
    Buchanan, J.W., Wypych, Alicja, Barrera, 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, Evan, and Wildland, A.D., 2025, Geochemical data from samples collected in 2023 for the Chena and Mount Harper projects, Big Delta, Circle, Fairbanks, and Eagle quadrangles, Alaska: Raw Data File RDF 2024-2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 5 p
    Moshrefzadeh, J.A., Buchanan, J.W., Naibert, T.J., Twelker, Evan, Newberry, R.J., Szumigala, D.J., Barrera, M.L., Norwood, L.P., Acosta, M.D., and Regan, S.P., 2025, Field station locations and magnetic susceptibility data collected in 2024 for the Chena and Steese projects, Yukon-Tanana Uplands, Alaska: Raw Data File RDF 2025-5, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 5 p
    Newberry, R.J., Bundtzen, T.K., Clautice, K.H., Combellick, R.A., Douglas, Tom, Laird, G.M., Liss, S.A., Pinney, D.S., Reifenstuhl, R.R., and Solie, D.N., 1996, Preliminary geologic map of the Fairbanks mining district, Alaska: Public Data File PDF 96-16, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 17 p., 2 sheets, scale 1:63,360
    Newberry, R.J., and Twelker, Evan, 2021, Metamorphism of the Ladue River-Mount Fairplay area: Report of Investigation RI 2021-5B, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: p. 33-39
    Twelker, Evan, Newberry, R.J., Naibert, T.J., and Wypych, Alicja, 2025, Bedrock geologic map of the Richardson Mining District, Big Delta Quadrangle, Alaska: Preliminary Interpretive Report PIR 2025-2A, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:100,000

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

  1. How well have the observations been checked?
    The accompanying report and data tables provide a comprehensive discussion of processing methods, with errors reported in the tables where applicable. This data is being released as part of the DGGS RDF series, which includes content describing approved techniques and methods for the collection, storage, visualization, analysis, and interpretation of scientific data. While the information has been reviewed by several geologists familiar with the study area, the data and report have not undergone formal review for technical content or conformity to DGGS editorial standards. For inquiries regarding analytical values or procedures, the originating lab is the best point of contact.
  2. How accurate are the geographic locations?
    Location data for field stations were collected using GPS-enabled tablets or smartphones running the ESRI Field Maps app. The devices have reported errors between 10 and 12 m. Latitude and longitude are reported in the WGS84 datum.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This data release is complete.
  5. How consistent are the relationships among the observations, including topology?
    Not applicable

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? RDF 2025-13
  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: 31-Jul-2025
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 Thu Jul 31 18:23:17 2025