40Ar/39Ar data, Ray Mountains area, Bettles Quadrangle, Alaska

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Frequently anticipated questions:

What does this data set describe?

Title: 40Ar/39Ar data, Ray Mountains area, Bettles Quadrangle, Alaska
Abstract:
40Ar/39Ar analyses were performed on igneous rocks from the Ray Mountains area of west-central Alaska. The plutonic samples have ages from about 89 Ma to 109 Ma, while the volcanic samples show ranges from about 30 Ma to 64 Ma. The three volcanic samples fall into two age groups: the younger sample, a basalt, has an age of about 30 Ma, while the two older, rhyolitic samples fall between 58 Ma and 64 Ma. Analyses were performed by the University of Alaska Fairbanks Geochronology Laboratory, and results were reported by Paul Layer and Jeff Benowitz. Products included in this data release are: a summary of sample collection method; the laboratory report, analytical data tables and associated metadata; and plots of the 40Ar/39Ar age spectra, Ca/K ratios, and Cl/K ratios. All components of this data release are available for download on the DGGS website at no charge.
Supplemental_Information:
The DGGS metadata standard extends the FGDC standard to include elements that are required to facilitate our internal data management. These elements, referred to as "layers," group and describe files that have intrinsic logical or topological relationships and correspond to subdirectories within the data distribution package. The metadata layer provides an FGDC metadata file and may include other documentation files. Attribute information for each data layer is described in this metadata file under the "Entity_and_Attribute_Information" section. Data layer contents: 
border:    Outline of the study area
arar-summary-data-locations:    Identification numbers, coordinates, sample descriptions, and summary ages of each sample
step-heating-data:    Power output levels and resultant measurements from each sample run
  1. How should this data set be cited?

    Tuzzolino, A.L., Newberry, R.J., Benowitz, J.A., Layer, P.W., and Freeman, L.K., 2014, 40Ar/39Ar data, Ray Mountains area, Bettles Quadrangle, Alaska: Raw Data File RDF 2014-19, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 12 p.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -150.455470
    East_Bounding_Coordinate: -150.068310
    North_Bounding_Coordinate: 66.619410
    South_Bounding_Coordinate: 66.057300

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 2012
    Ending_Date: 2014
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: report,

  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 0.00001. Longitudes are given to the nearest 0.00001. Latitude and longitude values are specified in decimal degrees.

      The horizontal datum used is North American Datum of 1983.
      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?

    rdf2014-19-border.shp
    Outline of the study area (Source: Alaska Division of Geological & Geophysical Surveys)

    rdf2014-19-arar-summary-data-locations.csv
    Identification numbers, coordinates, sample descriptions, and summary ages of each sample (Source: Alaska Division of Geological & Geophysical Surveys)

    SAMPLE
    Label assigned in the field to identify the sample. (Source: Alaska Division of Geological & Geophysical Surveys)

    Generic example of a sample identifier: YYAAA9999X: YY=last two digits of year, AAA=geologist's initials (one to three characters), 9999=unique station number, X= optional alpha character which indicates that multiple samples were collected at a given location or that multiple observations were recorded in the project database.

    LAB_SAMPLE_NUMBER
    Label used by the lab to identify the sample. (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    The lab sample number is typically identical to the field sample number. However, in some cases, the sample number provided by the lab does differ from the number assigned in the field. We provide both numbers to document instances in which the sample numbers in the lab files differ from the field sample number.

    COLLECTOR
    The geologist who collected the sample. (Source: Alaska Division of Geological & Geophysical Surveys)

    The samples presented in this report were collected by the authors or other DGGS staff.

    LONGITUDE
    Longitude, NAD83 (Source: Alaska Division of Geological & Geophysical Surveys)

    Range of values
    Minimum:-150.45547
    Maximum:-150.06831
    Units:decimal degrees

    LATITUDE
    Latitude, NAD83 (Source: Alaska Division of Geological & Geophysical Surveys)

    Range of values
    Minimum:66.0573
    Maximum:66.61941
    Units:decimal degrees

    MAP_UNIT
    The interpreted map unit of the sample. (Source: Alaska Division of Geological & Geophysical Surveys)

    Map unit designations are based on published mapping. The reference to the originating publication is noted in the description field.

    DESCRIPTION
    Description of the sample (Source: Alaska Division of Geological & Geophysical Surveys)

    Characters 1 to 254 of a brief sample or station description.

    DESCRIP_2
    Extension of the sample or station description for descriptions which are greater than 254 characters in length (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    NULLBlank (NULL) values indicate that the descriptive text is shorter than 254 characters.

    Characters greater than 254 of the sample or station description.

    DESCRIP_3
    Extension of the sample or station description for descriptions which are greater than 509 characters in length (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    NULLBlank (NULL) values indicate that the descriptive text is shorter than 509 characters.

    Characters greater than 509 of the sample or station description.

    DATED_MATERIAL
    Indicates the type of material that was used for analysis (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    The type of material that was selected for dating varied according to mineral composition and grainsize of the submitted rock sample. This field specifies whether the age was derived from a mineral separate (generally 1 to 10 individual crystals dated together as a single run), a single crystal, or the whole rock.

    MINERAL
    Indicates the mineral that was used for analysis (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    ValueDefinition
    NULLA NULL or blank values indicates that the sample was a whole rock or that the mineral type was not recorded by the lab

    The minerals selected for dating would typically be grains of biotite, hornblende, or muscovite.

    INTEGRATED_AGE_MA
    Integrated age and age error in million years (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    The values are a concatenation of the integrated age determination and the calculated error associated with the integrated age determination

    PLATEAU_AGE_MA
    Plateau age and age error in million years (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    The values are a concatenation of the plateau age determination and the calculated error associated with the plateau age determination

    PLATEAU_PERCENT_39AR
    Value in percent of the 39 Ar used in that portion of the spectrum to determine the plateau age (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:51.7
    Maximum:100
    Units:percent

    PLATEAU_MSWD
    The mean square weighted deviation of the plateau age calculation (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:0.41
    Maximum:1.39

    PLATEAU_REMARKS
    Comments and additional values that pertain to the plateau age determination method or interpretation. (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Free text

    ISOCHRON_AGE
    Isochon age and age error in million years (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    ValueDefinition
    NULLA NULL or blank values indicates that the ISOCHRON_AGE value was not provided by the lab

    The values are a concatenation of the isochron age determination and the calculated error associated with the isochron age determination

    ISOCHRON_MSWD
    The mean square weighted deviation of the isochron age calculation (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    ValueDefinition
    NULLA NULL or blank values indicates that the value was not calculated by the lab

    Range of values
    Minimum:0.28
    Maximum:1.04

    ISOCHRON_REMARKS
    Comments and additional values that pertain to the isochon age determination method or interpretation. (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    ValueDefinition
    NULLA NULL or blank values indicates that the ISOCHRON_REMARKS value was not provided by the lab

    Free text

    PREFERRED
    Indicates preferred age. (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    A discussion of the preferred age for each analysis is provided in the accompanying lab report. The possible values are: plateau, isochron, or integrated.

    LAB_NOTES
    Additional information provided by the lab (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Free text

    rdf2014-19-step-heating-data.csv
    Power output levels and resultant measurements from each sample run (Source: Alaska Division of Geological & Geophysical Surveys)

    SAMPLE
    Label assigned in the field to identify the sample. (Source: Alaska Division of Geological & Geophysical Surveys)

    Generic example of a sample identifier: YYAAA9999X: YY=last two digits of year, AAA=geologist's initials (one to three characters), 9999=unique station number, X= optional alpha character which indicates that multiple samples were collected at a given location or that multiple observations were recorded in the project database.

    LAB_SAMPLE_NUMBER
    Label used by the lab to identify the sample. (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    The lab sample number is typically identical to the field sample number. However, in some cases, the sample number provided by the lab does differ from the number assigned in the field. We provide both numbers to document instances in which the sample numbers in the lab files differ from the field sample number.

    Laser_mW
    Laser output level in megawatts (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    ValueDefinition
    NULLA NULL or blank values indicates that the values in the row were calculated by weighting the individual heating steps by the fraction of 39Ar released.

    Range of values
    Minimum:500
    Maximum:9000
    Units:megawatts

    Integrated
    We indicate whether the values in the row were derived from a heating step or calculated by weighting the individual heating steps by the fraction of 39Ar released. (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    NULLThe values in the row were derived from a heating step
    Integratedthe values in this row were calculated by weighting the individual heating steps by the fraction of 39Ar released

    Cum39Ar
    Cumulative ratio of 39Argon released at this step (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    ValueDefinition
    NULLA NULL or blank values indicates that the value was not applicable or not calculated by the lab

    Range of values
    Minimum:0.0004
    Maximum:1

    Me40Ar39Ar
    Measured 40Ar/39Ar ratio for each heating step, corrected for blank and 39Ar decay (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:6.23397
    Maximum:299.18061

    Er40Ar39Ar
    The one sigma error for each 40Ar/39Ar measurement (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:0.01575
    Maximum:14.00278

    Me37Ar39Ar
    The ratio of measured 37Ar to measured 39Ar for each heating interval for each sample corrected for blank and 37Ar and 39Ar decay (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:-8.45407
    Maximum:14.89384

    Er37Ar39Ar
    The one sigma error for each 37Ar/39Ar measurement (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:0.00025
    Maximum:3.41217

    Me36Ar39Ar
    Ratio of measured 36Ar to measured 39Ar for each step interval for each sample corrected for blank and 39Ar decay (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:-0.00736
    Maximum:0.93589

    Er36Ar39Ar
    The one sigma error for each 36Ar/39Ar measurement (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:0.00004
    Maximum:0.07239

    Atm40Ar
    Percent of 40Ar which is atmospheric in composition at each step level (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:-12.60286
    Maximum:98.38922

    ErAtm40Ar
    The one sigma error for the percent of 40Ar which is atmospheric in composition at each step level (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:0.10481
    Maximum:46.30453

    MeCaK
    Ratio of Calcium to Potassium as determined from 37Ar/39Ar (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:-15.41999
    Maximum:27.61865

    ErCaK
    The one sigma error for each Ca/K determination (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:0.00045
    Maximum:6.22946

    MeClK
    Ratio of Chlorine to Potassium as determined from 38Ar/39Ar (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:-0.00059
    Maximum:0.02247

    ErClK
    The one sigma error for each Cl/K determination (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:0.00002
    Maximum:0.01068

    Er40ArRad39ArK
    One sigma error for each 40ArRad/39ArK value (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:0.01987
    Maximum:16.46962

    AgeMa
    Calculated age for each temperature step for each sample (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:8.87
    Maximum:124.85
    Units:MA

    ErAgeMa
    One sigma error of the age determination of each heating step (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    Range of values
    Minimum:0.21
    Maximum:75.37
    Units:MA

    WeightedAverageOfJFromStandards
    J value, calculated from the weighted average of standards placed in various positions in the nuclear reactor (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

    WeightedAverageOfJFromStandards value and error

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?

    This project is funded through the Governor's Strategic and Critical Minerals Assessment Capital Improvement Project, a component of the ongoing Alaska Airborne Geophysical/Geological Mineral Inventory Program funded by the Alaska State Legislature and managed by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys.

  3. To whom should users address questions about the data?

    Alaska Division of Geological & Geophysical Surveys
    GIS Manager
    3354 College Road
    Fairbanks, AK 99709-3707
    USA

    (907)451-5020 (voice)
    dggsgis@alaska.gov

    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays

Why was the data set created?

DGGS conducted a multi-year project from 2012 through 2013 studying the geology and economic potential of rare-earth elements (REEs) and base metals in the Ray Mountains in the Beaver, Bettles, Livengood, and Tanana quadrangles (Bachmann and others, 2013). As part of the bedrock geologic mapping, seven samples in the Bettles Quadrangle were collected for geochronologic analyses using 40Ar/39Ar techniques. These new age dates will allow us to better evaluate the geochronology of the granitic rocks that are the apparent source of the alluvial REE resources, and the geochronology of the volcanic rocks that relate to the development of the basins hosting the alluvial 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: 2013 (process 1 of 3)
    Fieldwork - Field geologists (2012-2013) collected rock samples from surface outcrops. Care was taken to collect fresh, unweathered samples displaying, when possible, sufficiently large grains for mineral separate sampling.

    Date: 2013 (process 2 of 3)
    Sample preparation and analysis - Prior to processing, thin sections of the samples were petrographically inspected to ensure that mineral specimens selected for dating were free of alteration. Rock samples that we found to be suitable for dating by 40Ar/39Ar geochronology analysis were submitted to the Geochronology Laboratory at the University of Alaska Fairbanks (UAF) where they were dated according to the protocols outlined in the accompanying report.

    Date: 2014 (process 3 of 3)
    Coordinate system conversion - The originating coordinate system for each sample varied according to the GPS settings specified by the collector. To provide a consistent coordinate system for all samples, all location coordinates were converted to decimal degrees, North American Datum of 1983.

  3. What similar or related data should the user be aware of?

    Bachmann, E.N., Blessington, M.J., Freeman, L.K., Newberry, R.J., Tuzzolino, A.L., Wright, T.C., and Wylie, William, 2013, Geochemical major-oxide, minor-oxide, trace-element, and rare-earth-element data from rocks and stream sediments collected in 2012 in the Ray Mountains area, Beaver, Bettles, Livengood, and Tanana quadrangles, Alaska: Raw Data File RDF 2013-5, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 4 p
    Blessington, M.J., Reioux, D.A., and Werdon, M.B., 2013, Analyses of historic U.S. Bureau of Mines rock and heavy mineral concentrate samples for geochemical trace-element and rare-earth element data--Ray Mountains and Kanuti-Hodzana uplands area, Alaska: Raw Data File RDF 2013-7, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 p
    Tuzzolino, A.L., Newberry, R.J., and Freeman, L.K., 2013, Rare-earth-element (REE) potential in the Ray Mountains area, central Alaska (poster): Alaska Miners Association Annual Convention, November 4-10, 2013: Poster and Presentation Tuzzolino, A.L. and others, 2013, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet

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

  1. How well have the observations been checked?

    Coordinates of sample locations were determined by the geologists in the field using handheld GPS units. Sample numbers were recorded in the field on sample bags and on field note sheets. The sample location table was cross checked for consistency against the sample numbers recorded on the bags. Laboratory sample numbers were generated by the UAF geochronology lab from the a list provided by DGGS. See text report for additional discussion of laboratory procedures. Lab results and interpretations were examined by the DGGS geologists to ensure that they are reasonable given the geologic context of the sample.

  2. How accurate are the geographic locations?

    Locations were recorded using handheld, WAAS-enabled GPS devices. WAAS-enabled GPS devices have a reported error of about 1 m (NSTB/WAAS T&E Team, 2006). Depending on degradation of the WAAS and GPS signals, the horizontal position error of sample locations in this report is in the range of 1-10 m. The originating coordinate system for each sample varied according to the GPS settings specified by the collector. To provide a consistent coordinate system for all samples, all location coordinates were converted to decimal degrees, North American Datum of 1983 (NAD 83).

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    Users should note that the interpretive summaries that are provided in the text report have been lightly edited for clarity but are generally provided as received from the lab.

  5. How consistent are the relationships among the observations, including topology?

    No topologic relationships are present in the data. We plotted the data points using GIS software to ensure that they are correctly located and we visually reviewed the sample identification numbers and other attribute values to ensure that they are free of typological errors.

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
    3354 College Road
    Fairbanks, AK 99709-3707
    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 (<http://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 2014-19

  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-Oct-2014
Metadata author:
Alaska Division of Geological & Geophysical Surveys
Metadata Manager
3354 College Road
Fairbanks, AK 99709-3707
USA

(907)451-5020 (voice)

Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.9.21 on Fri Oct 10 13:32:38 2014