Geochemical data from samples collected in 2020 and 2021 for the Western Tanacross project, Tanacross Quadrangle, Alaska

Metadata also available as - [Parseable text] - [XML]

Frequently anticipated questions:

What does this data set describe?

Title:
Geochemical data from samples collected in 2020 and 2021 for the Western Tanacross project, Tanacross Quadrangle, Alaska
Abstract:
During the 2021 field season, geologists from the Alaska Division of Geological & Geophysical Surveys (DGGS) conducted 1:100,000-scale bedrock geologic mapping of ~2600 mi2 (~6900 km2) within the Tanacross and Eagle quadrangles. The field areas for the Western Tanacross project are approximately 20 miles north and southwest of Tok. Prospects in the region include Stibnite Creek, Tushtena, Taurus, and others. Much of the field area was mapped at 1:250,000 scale by the U.S. Geological Survey (USGS) in the 1960s (Foster, 1970). This project aims to produce more detailed and modern geologic maps and supporting datasets that will promote mineral resource exploration in eastern interior Alaska. Highlights of this DGGS western Tanacross geochemical report include precise location and sampling of the Discovery Zone, Dave's Zone, Eagle, Mosquito, North Mosquito Flats, Peternie, North Peternie, Bush, Sixtymile Butte, and VABM West prospects. Discovery Zone samples returned the highest Au values: 21ET178-4.94 ppm Au; 21ET179-2.86 ppm Au, with arsenic (As) of 42,500 ppm and 21,900 ppm, respectively. Sample 21ET178 has also elevated silver (Ag) at 14.35 ppm. Three samples from Dave's Zone returned over 1 ppm Au values: 21ET170-1.77 ppm; 21ET171-1.51 ppm; and 21ET164-1.03 ppm. Similar to the Discovery zone, those samples have high As: 9,690 ppm, 7,880 ppm, and 3,110 ppm, respectively. Sample 21ET171 has over 27 ppm of Ag. An amphibolite sample from the southern part of the Western Tanacross project, just east from Robertson River has 0.015 ppm of palladium (Pd) accompanied by 0.0027 ppm of platinum (Pt). The DGGS map area includes a section of pre-Mississippian to Permian metasedimentary and metaigneous rocks as well as Triassic to Paleogene intrusive and volcanic rocks. The analytical data tables associated with this report are available through the Alaska Geochemistry database (https://maps.dggs.alaska.gov/geochem). For a direct link to this data release, see http://doi.org/10.14509/30844.
Supplemental_Information: 
geochemistry-download:    Digital data available through the Alaska Geochemistry database online. Download files include data, analytical methods, and detection limits.
  1. How might this data set be cited?
    Wypych, Alicja, Gavel, M.M., Naibert, T.J., Avirett, D.F., Barrera, M.L., Hubbard, A.K., Newberry, R.J., Regan, S.P., Twelker, Evan, Wildland, A.D., and Wyatt, W.C., 2022, Geochemical data from samples collected in 2020 and 2021 for the Western Tanacross project, Tanacross Quadrangle, Alaska: Raw Data File RDF 2022-5, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 3 p.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -143.989801
    East_Bounding_Coordinate: -141.832871
    North_Bounding_Coordinate: 64.248187
    South_Bounding_Coordinate: 63.252512
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2021
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: report, and, digital, data
  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 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in decimal degrees. The horizontal datum used is WGS84.
      The ellipsoid used is WGS 84.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257223563000025.
  7. How does the data set describe geographic features?
    geochemistry-download
    Digital data available through the Alaska Geochemistry database online. Download files include data, analytical methods, and detection limits. (Source: Alaska Division of Geological & Geophysical Surveys (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 DGGS Western Tanacross Project was funded by State of Alaska General Funds and the U.S. Geological Survey under Cooperative Agreement Number G20AC00156. Disclaimer: 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.
  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?

Major- and trace-element geochemistry was obtained for metamorphic rocks to help distinguish between igneous and sedimentary protoliths, and for igneous rocks to characterize and differentiate Mesozoic and Cenozoic magmatic events in the area. The project area is of current and historic interest for potential mineral resource development, including quartz vein gold (Au) mineralization, placer Au deposits, granite-hosted tin (Sn) mineralization, and intrusion-related copper (Cu)-Au deposits.

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: 2021 (process 1 of 5)
    Field data collection - During the 2021 field season, geologists from the Alaska Division of Geological & Geophysical Surveys (DGGS) conducted 1:100,000-scale bedrock geologic mapping of ~2600 mi2 (~6900 km2) within the Tanacross and Eagle quadrangles.
    Date: 2021 (process 2 of 5)
    Sample selection - Rock samples were collected for two different purposes. First, samples of visibly mineralized or altered rock were preferentially collected and analyzed for trace-element geochemistry. Second, igneous and metaigneous rocks showing little alteration or weathering were collected for whole-rock major-oxide, minor-oxide, and trace-element analyses to aid in classification and study of petrogenesis and tectonic setting. Most samples are grab samples, which were collected for their overall representation of the outcrop. However, a few samples are select samples, which were more deliberately collected from a specific feature, as noted in the sample field description. Rock outcrop accounts for much less than one percent of the study area, consequently, many of the rock samples were collected from up to 1-meter-deep pits dug with shovels into rocky colluvial deposits below the surficial loess.
    Date: 2019 (process 3 of 5)
    Sample preparation - Rock samples were processed by ALS Geochemistry using their PREP-31 package. The samples were crushed to greater than 70 percent passing 2 mm, and a 250 g split was pulverized to greater than 85 percent passing 75 microns. After each sample crushing, the pulverizers were cleaned with barren material. Prior to crushing, samples for whole-rock analysis were trimmed with a rock saw by DGGS staff to remove weathering.
    Date: 2021 (process 4 of 5)
    Major- and trace-element compositions - Major- and trace-element values for rock samples were determined by ALS Geochemistry method ME-MS61: Four-acid digestion followed by inductively-coupled plasma-atomic emission spectrometry (ICP-AES) and inductively-coupled plasma-mass spectroscopy (ICP-MS); Au values were analyzed using flux digestion and fire assay and ICP-AES (ALS Geochemistry method Au-ICP21). Samples that exceeded detection limits for elements of interest were reanalyzed using specific elemental tests. Over-limit values for As and S were analyzed using four-acid digestion followed by inductively-coupled plasma-atomic emission spectrometry (ALS Geochemistry method ME-OG62).
    Date: 2021 (process 5 of 5)
    Whole-rock geochemistry - Whole-rock geochemistry samples and major- and minor- oxides were analyzed by lithium borate fusion digestion and ICP-AES (ALS Geochemistry method ME-ICP06). Trace elements, including rare-earth elements, were determined using lithium metaborate fusion digestion and ICP-MS (ALS Geochemistry method ME-MS81). Ag, Cd, Co, Cu, Li, Mo, Ni, Pb, Sc, and Zn were determined by four-acid digestion and ICP-AES (ALS Geochemistry method ME-4ACD81); and As, Bi, Hg, In, Re, Sb, Se, Te, and Tl were determined by aqua regia digestion followed by ICP-MS (ALS Geochemistry method ME-MS42). Total C and S were analyzed by Leco furnace (ALS Geochemistry methods C-IR07 and S-IR08, respectively). Pt, Pd and Au were determined by fire assay with ICP-MS finish (ALS Precious Metals method PGM-MS23)
  3. What similar or related data should the user be aware of?
    Gavel, M.M., Wypych, Alicja, Naibert, T.J., Avirett, D.F., Barrera, M.L., Hubbard, A.K., Newberry, R.J., Regan, S.P., Twelker, Evan, Wildland, A.D., and Wyatt, W.C., 2022, Field station locations and magnetic susceptibility data collected in 2020 and 2021 for the Western Tanacross project, Tanacross and Eagle quadrangles, Alaska: Raw Data File RDF 2022-3, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 p

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

  1. How well have the observations been checked?
    Samples were analyzed for a variety of suites of major and trace elements depending on the sample type. In addition to ALS Geochemistry' accredited (ISO/IEC 17025-2005) internal quality-control program, DGGS monitored analysis quality with at least one standard reference material per batch of 20 analyses.
  2. How accurate are the geographic locations?
    Location data were collected using GPS-enabled tablets and smartphones running the ESRI Collector App. The devices have a reported error of about 10 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 2022-5
  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: 10-Mar-2022
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 Wed Mar 09 17:23:54 2022