40Ar/39Ar Isotopic Data and Ages for Rocks from the Yukon-Tanana Upland of Eastern Alaska and the Northern Aleutian Range of South-Central Alaska

Identification_Information:

Citation:

Citation_Information:

Originator: Jones III, J.V. (ORCID: 0000-0002-6602-5935)
Originator: Benowitz, J.A. (ORCID: 0000-0003-2294-9172)
Publication_Date: 20200921
Title:

Geospatial_Data_Presentation_Form: tabular digital data
Publication_Information:

Publication_Place: Anchorage, Alaska
Publisher: U.S. Geological Survey, Alaska Science Center

Other_Citation_Details:

Suggested citation: Jones III, J.V., and Benowitz, J.A., 2020, 40Ar/39Ar isotopic data and ages for rocks from the Yukon-Tanana upland of eastern Alaska and the northern Aleutian Range of south-central Alaska: U.S. Geological Survey data release, https://doi.org/10.5066/P96762V3.

Online_Linkage: https://doi.org/10.5066/P96762V3

Description:

Abstract:

This data set contains 40Ar/39Ar isotopic data and ages for rocks from the Yukon-Tanana upland of eastern Alaska and the northern Aleutian Range of south-central Alaska. The entire sample suite was collected as part of geological mapping and supporting geochemical and geochronological analysis were conducted from 2013 to 2019 by the Mineral Resources Program of the U.S. Geological Survey (USGS). Legacy bedrock samples archived from earlier USGS field investigations were also analyzed in some cases. Hornblende, muscovite, and (or) biotite were extracted from bedrock samples of igneous and metamorphic rocks and analyzed at the University of Alaska Fairbanks Geochronology Laboratory in order to determine the 40Ar/39Ar age of each mineral phase. The data tables accompanying this data release report the resulting 40Ar/39Ar analytical data and interpreted ages for each mineral separated from a bulk rock sample.

Purpose:

40Ar/39Ar dates of hornblende, muscovite, and (or) biotite aid in the interpretation of the thermal history of the mineral and the rock that contains it. In this study, 40Ar/39Ar dates were determined for one or more minerals from igneous and metamorphic bedrock samples. The 40Ar/39Ar ages help to constrain the age of regional deformation, metamorphism, and cooling and provide key insights into the geological and metallogenic evolution of large regions of eastern and south-central Alaska. These data will be used in support of multiple geological maps, reports, and journal articles that describe the geological framework and mineral resource potential of Alaska.

Time_Period_of_Content:

Time_Period_Information:

Single_Date/Time:

Calendar_Date: 2020

Currentness_Reference: publication date

Status:

Progress: Complete
Maintenance_and_Update_Frequency: None planned

Spatial_Domain:

Bounding_Coordinates:

West_Bounding_Coordinate: -153.5
East_Bounding_Coordinate: -141.0
North_Bounding_Coordinate: 64.5
South_Bounding_Coordinate: 60.2

Keywords:

Theme:

Theme_Keyword_Thesaurus: USGS Metadata Identifier
Theme_Keyword: USGS:ASC311

Theme:

Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: geoscientificInformation

Theme:

Theme_Keyword_Thesaurus: USGS Thesaurus
Theme_Keyword: geology
Theme_Keyword: geochronology
Theme_Keyword: potassium-argon analysis

Theme:

Theme_Keyword_Thesaurus: GeoRef Thesaurus
Theme_Keyword: Ar/Ar

Theme:

Theme_Keyword_Thesaurus: NASA GCMD Earth Science Keywords Thesaurus
Theme_Keyword: earth science

Place:

Place_Keyword_Thesaurus: USGS Geographic Names Information System (GNIS)
Place_Keyword: Alaska
Place_Keyword: Divide Mountain
Place_Keyword: Taylor Mountain
Place_Keyword: Mount Harper
Place_Keyword: Ladue River
Place_Keyword: Fortymile River
Place_Keyword: Sixty Mile River
Place_Keyword: Aleutian Range
Place_Keyword: Lake Clark
Place_Keyword: Neacola River
Place_Keyword: Drift River
Place_Keyword: Blockade Lake
Place_Keyword: McArthur River
Place_Keyword: Tlikakila River
Place_Keyword: Chokotonk River
Place_Keyword: Tuxedni River
Place_Keyword: Chigmit Mountains

Place:

Place_Keyword_Thesaurus: None
Place_Keyword: Yukon-Tanana upland

Access_Constraints: None
Use_Constraints:

None. Users are advised to read the metadata thoroughly to understand appropriate use and data limitations.

Point_of_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: U.S. Geological Survey
Contact_Person: James V. Jones

Contact_Position: Geologist
Contact_Address:

Address_Type: mailing and physical address
Address: 4210 University Drive
City: Anchorage
State_or_Province: Alaska
Postal_Code: 99508-4626
Country: U.S.A.

Contact_Voice_Telephone: 907-786-7000
Contact_Electronic_Mail_Address: ascweb@usgs.gov

Cross_Reference:

Citation_Information:

Originator: Jones III, J.V. (ORCID: 0000-0002-6602-5935)
Publication_Date: 2015
Title:

Tectonic and metallogenic evolution of the eastern Yukon-Tanana upland, Alaska

Geospatial_Data_Presentation_Form: web site
Series_Information:

Series_Name: Science Portal
Issue_Identification: 389

Publication_Information:

Publication_Place: Anchorage, Alaska
Publisher: U.S. Geological Survey, Alaska Science Center

Other_Citation_Details:

This is a link to the broader USGS Alaska Science Center research project supported by these data. Users will find a description of the research project and links to associated reports, publications, and data products.

Online_Linkage: https://alaska.usgs.gov/portal/project.php?project_id=389

Cross_Reference:

Citation_Information:

Originator: Jones III, J.V. (ORCID: 0000-0002-6602-5935)
Publication_Date: 2014
Title:

Metallogeny and tectonics of the Neacola Mountains and Lake Clark region, south-central Alaska

Geospatial_Data_Presentation_Form: web site
Series_Information:

Series_Name: Science Portal
Issue_Identification: 388

Publication_Information:

Publication_Place: Anchorage, Alaska
Publisher: U.S. Geological Survey, Alaska Science Center

Other_Citation_Details:

Online_Linkage: https://alaska.usgs.gov/portal/project.php?project_id=388

Data_Quality_Information:

Attribute_Accuracy:

Attribute_Accuracy_Report:

Mineral samples were irradiated with monitor mineral MMhb-1 with preferred age of 523.5 Ma (Renne et al, 1994). Samples and the monitors were step-heated or fused using a 6-watt argon-ion laser. Argon purification was achieved using a liquid nitrogen cold trap and SAES Zr-Al getter at 400 degrees C. The argon isotopes were measured and corrected for system blank and mass discrimination, as well as neutron induced reactions on calcium, potassium and chlorine. Typical full-system 8 min laser blank values (in moles) were generally 2e-16 mol 40Ar, 3e-18 mol 39Ar, 9e-18 mol 38Ar, and 2e-18 mol 37Ar, and 2e-18 mol 36Ar, which are 10-50 times smaller than the sample/standard volume fractions. Correction factors for nucleogenic interferences during irradiation were determined from irradiated CaF2 and K2SO4 and were: (39Ar/37Ar)Ca = 7.06e-4, (36Ar/37Ar)Ca = 2.79e-4, and (40Ar/39Ar)K = 0.0297. Mass discrimination was monitored by analyzing air shots with an assumed 40Ar/36Ar value of 295.5 (Nier, 1950). The mass discrimination during these experiments was 1.3% per mass unit. No significant variation in discrimination over the course of the analyses was measured and so a single value was used in data reduction. Ages with +/- 1 sigma error were calculated using the decay constants of Renne et al, 2010. The integrated age is the age given by the total gas measured and is equivalent to a potassium-argon (K-Ar) age. A plateau age is reported if three or more consecutive gas fractions representing at least 50 percent of the total gas released that are within two standard deviations of each other and with an overall Mean Square Weighted Deviation (MSWD) less than or equal to 2.5.

Logical_Consistency_Report:

No unexpected values are found in these data. Blank cells in the data tables indicate values were either not provided, not measured, or not calculated.

Completeness_Report: This data set is complete; no data were omitted.
Positional_Accuracy:

Horizontal_Positional_Accuracy:

Horizontal_Positional_Accuracy_Report:

All samples collected since 2014 have horizontal positions measured using hand-held GPS units with positional accuracy of 3 meters. The location for samples collected in 1974 were obtained from 1:63,360 scale topographic field sheets.

Lineage:

Source_Information:

Source_Citation:

Citation_Information:

Originator: Geochronology Laboratory at UAF
Publication_Date: 2019
Title: UAF 40Ar39Ar Methods
Publication_Information:

Publication_Place: Fairbanks, Alaska
Publisher: Geochronology Laboratory at University of Alaska Fairbanks

Other_Citation_Details:

This is a supplemental PDF document included in this data release. The file name is UAF_40Ar39Ar_methods.pdf.

Type_of_Source_Media: pdf file
Source_Time_Period_of_Content:

Time_Period_Information:

Single_Date/Time:

Calendar_Date: 2019

Source_Currentness_Reference: publication date

Source_Citation_Abbreviation: UAF 40Ar/39Ar methods
Source_Contribution:

Provides detailed description of laboratory methods for 40Ar/39Ar geochronology.

Source_Information:

Source_Citation:

Citation_Information:

Originator: Nier, A.O.
Publication_Date: 1950
Title:

A redetermination of the relative abundances of the isotopes of carbon, nitrogen, oxygen, argon, and potassium

Series_Information:

Series_Name: Physical Review
Issue_Identification: vol. 77, no. 6, p. 789

Online_Linkage: https://doi.org/10.1103/PhysRev.77.789

Type_of_Source_Media: journal article
Source_Time_Period_of_Content:

Time_Period_Information:

Single_Date/Time:

Calendar_Date: 1950

Source_Currentness_Reference: publication date

Source_Citation_Abbreviation: Nier, 1950
Source_Contribution: Calculation of argon isotope abundance ratios

Source_Information:

Source_Citation:

Citation_Information:

Originator: Renne, Paul R.
Originator: Deino, Alan L.
Originator: Walter, Robert C.
Originator: Turrin, Brent D.
Originator: Swisher, Carl C.
Originator: Becker, Tim A.
Originator: Curtis, Garniss H.
Originator: Sharp, Warren D.
Originator: Jaouni, Abdur-Rahim
Publication_Date: 1994
Title: Intercalibration of astronomical and radioisotopic time
Series_Information:

Series_Name: Geology
Issue_Identification: vol. 22, p. 783-786

Online_Linkage: https://doi.org/10.1130/0091-7613(1994)022<0783:IOAART>2.3.CO;2

Type_of_Source_Media: journal article
Source_Time_Period_of_Content:

Time_Period_Information:

Single_Date/Time:

Calendar_Date: 1994

Source_Currentness_Reference: publication date

Source_Citation_Abbreviation: Renne et al, 1994
Source_Contribution: Data on monitor mineral MMhb-1

Source_Information:

Source_Citation:

Citation_Information:

Originator: Renne, Paul R.
Originator: Mundil, Roland
Originator: Balco, Greg
Originator: Min, Kyoungwon
Originator: Ludwig, Kenneth R.
Publication_Date: 2010
Title:

Joint determination of 40K decay constants and 40Ar*/40K for the Fish Canyon sanidine standard, and improved accuracy for 40Ar/39Ar geochronology

Series_Information:

Series_Name: Geochimica et Cosmochimica Acta
Issue_Identification: vol. 74, p. 5349-5367

Online_Linkage: https://doi.org/10.1016/j.gca.2010.06.017

Type_of_Source_Media: journal article
Source_Time_Period_of_Content:

Time_Period_Information:

Single_Date/Time:

Calendar_Date: 2010

Source_Currentness_Reference: publication date

Source_Citation_Abbreviation: Renne et al, 2010
Source_Contribution: Decay constants

Process_Step:

Process_Description:

Mineral separation was done at the Geochronology Laboratory at the University of Alaska Fairbanks (UAF). For 40Ar/39Ar analysis, bulk rock samples were crushed, sieved, washed and hand-picked to obtain pure hornblende, biotite, and muscovite mineral separates. Samples and standards were wrapped in aluminum foil and loaded into aluminum cans of 2.5 cm diameter and 6 cm height. The samples were irradiated in position 5c of the uranium enriched research reactor of McMaster University in Hamilton, Ontario, Canada for 20 megawatt-hours. After irradiation, the samples and standards were returned to UAF and loaded into an ultra-high vacuum extraction line. The standards were fused, and the samples heated, using a 6-watt argon-ion laser. Argon purification was achieved using a liquid nitrogen cold trap and a SAES Zr-Al getter at 400 degrees C. The argon isotopes were analyzed in a VG-3600 mass spectrometer, fitted with a single Daly detector, and operated in peak mode.

Process_Date: 2019

Spatial_Data_Organization_Information:

Direct_Spatial_Reference_Method: Point

Spatial_Reference_Information:

Horizontal_Coordinate_System_Definition:

Geographic:

Latitude_Resolution: 0.0001
Longitude_Resolution: 0.0001
Geographic_Coordinate_Units: Decimal degrees

Geodetic_Model:

Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: GRS 1980
Semi-major_Axis: 6378137
Denominator_of_Flattening_Ratio: 298.257222101

Entity_and_Attribute_Information:

Detailed_Description:

Entity_Type:

Entity_Type_Label: geology_40Ar39ArData_Alaska_Jones.csv
Entity_Type_Definition:

Table of 40Ar/39Ar isotopic data, including heating power levels, measurements, and calculated age for each heating step. There are 811 records in this table.

Entity_Type_Definition_Source: Author defined

Attribute:

Attribute_Label: Sample
Attribute_Definition:

Sample identifier as collected in the field; an internal USGS identifier. Descriptive and locational information about the sample is provided in table geology_40Ar39ArSummary_Alaska_Jones.csv.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

Sample identifier; most labels consisting of the last two digits of the year collected, an abbreviation identifying the collector, and a number and possible suffix.

Attribute:

Attribute_Label: LabID
Attribute_Definition:

Sample name assigned by the laboratory corresponding to the USGS sample identifier and mineral analyzed.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Alphanumeric code consisting of UAF and a hyphenated number.

Attribute:

Attribute_Label: Lab
Attribute_Definition: Laboratory where analysis was conducted
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Enumerated_Domain:

Enumerated_Domain_Value: UAF
Enumerated_Domain_Value_Definition: Geochronology Laboratory, University of Alaska Fairbanks
Enumerated_Domain_Value_Definition_Source: Author defined

Attribute:

Attribute_Label: Sample_material
Attribute_Definition: Mineral analyzed
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

The following values are used in this data set: biotite, hornblende, and muscovite.

Attribute:

Attribute_Label: Monitor_mineral
Attribute_Definition:

Reference mineral used to monitor neutron flux and calculate the irradiation parameter, J.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Enumerated_Domain:

Enumerated_Domain_Value: MMhb-l
Enumerated_Domain_Value_Definition: hornblende standard for 40Ar/39Ar
Enumerated_Domain_Value_Definition_Source:

Samson, S.D., and Alexander, E.C., 1987, Calibration of the interlaboratory 40Ar/39Ar dating standard, MMhb1: Chemical Geology, v. 66, p. 27-34, https://doi.org/10.1016/0168-9622(87)90025-X. Renne, P.R., Deino, A.L., Walter, R.C., Turrin, B.D., Swisher, C.C., Becker, T.A., Curtis, G.H., Sharp, W.D., and Jaouni, A.R., 1994, Intercalibration of astronomical and radioisotope time: Geology, v. 22, p. 783-786, https://doi.org/10.1130/0091-7613(1994)022<0783:IOAART>2.3.CO;2.

Attribute:

Attribute_Label: Monitor_mineral_age
Attribute_Definition: Published age of the monitor mineral
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

The monitor mineral used for all analyses in this data set is MMhb-1 with age 523.5 Ma.

Attribute:

Attribute_Label: J_value
Attribute_Definition: Measure of neutron fluence
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.005069
Range_Domain_Maximum: 0.005650

Attribute:

Attribute_Label: J_unc
Attribute_Definition: Uncertainty (1-sigma) in measure of neutron fluence
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.000017
Range_Domain_Maximum: 0.000046

Attribute:

Attribute_Label: Laser_power_mW
Attribute_Definition:

Laser power setting, in milliwatt, for each heating step. Blank cells indicate an integrated analysis.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 500
Range_Domain_Maximum: 12000
Attribute_Units_of_Measure: mW (milliwatt)

Attribute:

Attribute_Label: Integrated
Attribute_Definition:

Integrated analysis indicates that values were calculated by weighting individual heating steps by the fraction of 39Ar released. Blank cells designate a heating step fraction.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

The term 'Integrated' indicates the values were calculated by weighting the individual heating steps by the fraction of 39Ar released.

Attribute:

Attribute_Label: 39Ar_cum
Attribute_Definition:

Cumulative 39Ar released at this step. Blank cells indicate an integrated analysis.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.00069
Range_Domain_Maximum: 1.00000
Attribute_Units_of_Measure: percentage in decimal format

Attribute:

Attribute_Label: 40Ar_mV
Attribute_Definition: Abundance of 40Ar in millivolt
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 4.9957
Range_Domain_Maximum: 38363.1091
Attribute_Units_of_Measure: mV (millivolt)

Attribute:

Attribute_Label: 40Ar_mV_unc
Attribute_Definition: Uncertainty (1-sigma) in 40Ar in millivolt
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.1100
Range_Domain_Maximum: 1890.1793
Attribute_Units_of_Measure: mV (millivolt)

Attribute:

Attribute_Label: 39Ar_mV
Attribute_Definition: Abundance of 39Ar in millivolt
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.1257
Range_Domain_Maximum: 3461.2629
Attribute_Units_of_Measure: mV (millivolt)

Attribute:

Attribute_Label: 39Ar_mV_unc
Attribute_Definition: Uncertainty (1-sigma) in 39Ar in millivolt
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.0163
Range_Domain_Maximum: 1.9715
Attribute_Units_of_Measure: mV (millivolt)

Attribute:

Attribute_Label: 38Ar_mV
Attribute_Definition: Abundance of 38Ar in millivolt
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: -0.0077
Range_Domain_Maximum: 181.3537
Attribute_Units_of_Measure: mV (millivolt)

Attribute:

Attribute_Label: 38Ar_mV_unc
Attribute_Definition: Uncertainty (1-sigma) in 38Ar in millivolt
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.0070
Range_Domain_Maximum: 0.3693
Attribute_Units_of_Measure: mV (millivolt)

Attribute:

Attribute_Label: 37Ar_mV
Attribute_Definition: Abundance of 37Ar in millivolt
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: -0.0013
Range_Domain_Maximum: 2.6300
Attribute_Units_of_Measure: mV (millivolt)

Attribute:

Attribute_Label: 37Ar_mV_unc
Attribute_Definition: Uncertainty (1-sigma) in 37Ar in millivolt
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.0180
Range_Domain_Maximum: 9.9773
Attribute_Units_of_Measure: mV (millivolt)

Attribute:

Attribute_Label: 36Ar_mV
Attribute_Definition: Abundance of 36Ar in millivolt
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: -1.4553
Range_Domain_Maximum: 139.3879
Attribute_Units_of_Measure: mV (millivolt)

Attribute:

Attribute_Label: 36Ar_mV_unc
Attribute_Definition: Uncertainty (1-sigma) of 36Ar in millivolt
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.0070
Range_Domain_Maximum: 1.5371
Attribute_Units_of_Measure: mV (millivolt)

Attribute:

Attribute_Label: Perc_atm_40Ar
Attribute_Definition: Percent atmospheric 40Ar in measurement
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: -88.16
Range_Domain_Maximum: 143.11
Attribute_Units_of_Measure: percent

Attribute:

Attribute_Label: Perc_atm_40Ar_unc
Attribute_Definition:

Uncertainty (1-sigma) in percent atmospheric 40Ar in measurement

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.07
Range_Domain_Maximum: 61.12
Attribute_Units_of_Measure: percent

Attribute:

Attribute_Label: Ca_K_ratio
Attribute_Definition:

Calcium to potassium ratio as determined from 37 argon derived from calcium and 39 argon derived from potassium; 37Ar(Ca)/39Ar(K).

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: -0.42547
Range_Domain_Maximum: 48.42797

Attribute:

Attribute_Label: Ca_K_ratio_unc
Attribute_Definition: Uncertainty (1-sigma) in calcium to potassium ratio
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.00025
Range_Domain_Maximum: 4.48215

Attribute:

Attribute_Label: Cl_K_ratio
Attribute_Definition:

Chlorine to potassium ratio as determined from 38 argon derived from chlorine and 39 argon derived from potassium; 38Ar(Cl)/39Ar(K).

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: -0.00413
Range_Domain_Maximum: 0.25133

Attribute:

Attribute_Label: Cl_K_ratio_unc
Attribute_Definition: Uncertainty (1-sigma) in chlorine to potassium ratio
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.00002
Range_Domain_Maximum: 0.03959

Attribute:

Attribute_Label: 40Ar_39Ar_K
Attribute_Definition: Ratio of radiogenic 40Ar to 39Ar derived from potassium
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: -501.69492
Range_Domain_Maximum: 205.36012

Attribute:

Attribute_Label: 40Ar_39Ar_K_unc
Attribute_Definition:

Uncertainty (1-sigma) in ratio of radiogenic 40Ar to 39Ar from potassium

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.02432
Range_Domain_Maximum: 92.36374

Attribute:

Attribute_Label: Age_Ma
Attribute_Definition:

Age calculated for each heating step from ratio of radiogenic 40Ar to 39Ar from potassium, in millions of years.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: -257083.62
Range_Domain_Maximum: 1387.19
Attribute_Units_of_Measure: Ma

Attribute:

Attribute_Label: Age_Ma_unc
Attribute_Definition: Uncertainty (1-sigma) in calculated age, in millions of years
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.36
Range_Domain_Maximum: 1108.12
Attribute_Units_of_Measure: Ma

Detailed_Description:

Entity_Type:

Entity_Type_Label: geology_40Ar39ArSummary_Alaska_Jones.csv
Entity_Type_Definition:

Table with descriptive sample information, including location, rock description, and summary of geochronology analyses. This table contains 91 records and is presented in comma separated value (CSV) format.

Entity_Type_Definition_Source: Author defined

Attribute:

Attribute_Label: Sample
Attribute_Definition:

Sample identifier as collected in the field; an internal USGS identifier.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

Sample identifier; most labels consisting of the last two digits of the year collected, an abbreviation identifying the collector, and a number and possible suffix.

Attribute:

Attribute_Label: AK_Region
Attribute_Definition: Region of Alaska where sample was collected
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

Values in this data set include 'Eastern Alaska' and 'South-central Alaska'.

Attribute:

Attribute_Label: AK_Subregion
Attribute_Definition: Geographic area where sample was collected
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

Values in this data set include 'Lake Clark/Neacola Mountains' and 'Yukon-Tanana upland'.

Attribute:

Attribute_Label: Latitude
Attribute_Definition: Latitude given in decimal degrees; datum NAD83
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 60.2381
Range_Domain_Maximum: 64.4066
Attribute_Units_of_Measure: decimal degree

Attribute:

Attribute_Label: Longitude
Attribute_Definition: Longitude given in decimal degrees; datum NAD83
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: -153.4093
Range_Domain_Maximum: -141.0140
Attribute_Units_of_Measure: decimal degree

Attribute:

Attribute_Label: Rock_Class
Attribute_Definition: Basic rock classification of the sample
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Attributes in the data set are 'igneous' and 'metamorphic'

Attribute:

Attribute_Label: Rock_Type
Attribute_Definition: Sample rock type
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: General rock description

Attribute:

Attribute_Label: Rock_Comment
Attribute_Definition: A more detailed rock description than Rock_Type
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: A more descriptive rock description than Rock_Type

Attribute:

Attribute_Label: Analysis_Type
Attribute_Definition: type of geochronologic analysis
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Enumerated_Domain:

Enumerated_Domain_Value: 40Ar/39Ar
Enumerated_Domain_Value_Definition: argon-argon radiometric dating
Enumerated_Domain_Value_Definition_Source: Author defined

Attribute:

Attribute_Label: Analysis_Lab
Attribute_Definition: Laboratory where analysis was conducted
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Enumerated_Domain:

Enumerated_Domain_Value: UAF
Enumerated_Domain_Value_Definition: Geochronology Laboratory, University of Alaska Fairbanks
Enumerated_Domain_Value_Definition_Source: Author defined

Attribute:

Attribute_Label: LabID
Attribute_Definition:

Sample name assigned by the laboratory corresponding to the USGS sample identifier and mineral analyzed.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Alphanumeric code consisting of UAF and a hyphenated number

Attribute:

Attribute_Label: Sample_Material
Attribute_Definition: Mineral analyzed
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

The following values are used in this data set: biotite, hornblende, and muscovite.

Attribute:

Attribute_Label: Preferred_40Ar_39Ar_Age
Attribute_Definition:

Preferred 40Ar_39Ar_Age of the sample material, in millions of years. Value -9999 indicates the analysis is not reliable and so no preferred age is reported.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 24.6
Range_Domain_Maximum: 265.7
Attribute_Units_of_Measure: Ma

Attribute:

Attribute_Label: Preferred_40Ar_39Ar_Age_unc
Attribute_Definition:

Uncertainty (1-sigma) of the preferred 40Ar/39Ar age, in millions of years. Value -9999 indicates the analysis is not reliable.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.4
Range_Domain_Maximum: 7.5
Attribute_Units_of_Measure: Ma

Attribute:

Attribute_Label: Preferred_40Ar_39Ar_Age_type
Attribute_Definition: Method used to calculate Preferred_40Ar_39Ar_Age
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

Values include variations of integrated age, isochron age, plateau age, weighted average, or no reliable age.

Attribute:

Attribute_Label: Preferred_40Ar_39Ar_Age_comment
Attribute_Definition: Details on how Preferred_40Ar_39Ar_Age was calculated.
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Details on how Preferred_40Ar_39Ar_Age was calculated

Attribute:

Attribute_Label: Integrated_40Ar_39Ar_Age
Attribute_Definition:

Integrated 40Ar/39Ar age, in millions of years, calculated from total gas measured

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 24.6
Range_Domain_Maximum: 704.5
Attribute_Units_of_Measure: Ma

Attribute:

Attribute_Label: Integrated_40Ar_39Ar_Age_unc
Attribute_Definition:

Uncertainty (1-sigma) on the integrated 40Ar/39Ar age, in millions of years

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.4
Range_Domain_Maximum: 8.0
Attribute_Units_of_Measure: Ma

Attribute:

Attribute_Label: Plateau_40Ar_39Ar_Age
Attribute_Definition:

Plateau 40Ar/39Ar age, in millions of years, calculated from three or more consecutive gas fractions representing more than 50% of the total gas released that are within two standard deviations of each other and with an overall Mean Square Weighted Deviation (MSWD) less than or equal to 2.5. Value -9999 indicates data did not meet the criteria necessary to calculate a plateau age.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 24.6
Range_Domain_Maximum: 265.7
Attribute_Units_of_Measure: Ma

Attribute:

Attribute_Label: Plateau_40Ar_39Ar_Age_unc
Attribute_Definition:

Uncertainty (1-sigma) on the plateau 40Ar/39Ar age, in millions of years. Value -9999 indicates data did not meet the criteria necessary to calculate a plateau age.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.4
Range_Domain_Maximum: 7.5
Attribute_Units_of_Measure: Ma

Attribute:

Attribute_Label: Plateau_40Ar_39Ar_Age_MSWD
Attribute_Definition:

Mean square of weighted deviates (MSWD) on calculated plateau age. Value -9999 denotes no data.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.05
Range_Domain_Maximum: 13.09

Attribute:

Attribute_Label: Plateau_40Ar_39Ar_Age_comment
Attribute_Definition:

Comments on the plateau age, including number of heating steps used and percentage of 39Ar released.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

Comments on the plateau age, including number of heating steps used and percentage of 39Ar released.

Attribute:

Attribute_Label: Isochron_40Ar_39Ar_Age
Attribute_Definition:

Isochron 40Ar/39Ar age in millions of years. Blank cells are present.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 33.4
Range_Domain_Maximum: 125.1
Attribute_Units_of_Measure: Ma

Attribute:

Attribute_Label: Isochron_40Ar_39Ar_Age_unc
Attribute_Definition:

Uncertainty (1-sigma) on the isochron 40Ar/39Ar age, in millions of years. Blank cells are present.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.6
Range_Domain_Maximum: 8.3
Attribute_Units_of_Measure: Ma

Attribute:

Attribute_Label: Isochron_40Ar_39Ar_Age_MSWD
Attribute_Definition:

Mean square of weighted deviates (MSWD) on calculated isochron age. Blank cells are present.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.52
Range_Domain_Maximum: 2.00

Attribute:

Attribute_Label: Isochron_40Ar_39Ar_Age_comment
Attribute_Definition:

Comments on the isochron age; gives number of heating steps included in calculation. Blank cells are present.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

Comments on the isochron age; gives number of heating steps included in calculation.

Attribute:

Attribute_Label: 40Ar_36Ar_initial
Attribute_Definition:

Initial 40Ar/36Ar calculated from isochron. Blank cells are present.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 280.7
Range_Domain_Maximum: 317.4

Attribute:

Attribute_Label: 40Ar_36Ar_initial_unc
Attribute_Definition:

Uncertainty (1-sigma) of initial 40Ar/36Ar calculated from isochron. Blank cells are present.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 3.9
Range_Domain_Maximum: 28.7

Detailed_Description:

Entity_Type:

Entity_Type_Label: geology_40Ar39ArDataDictionary_Alaska_Jones.csv
Entity_Type_Definition:

Table listing the name of all fields in each table, with a brief description of the field and the data units, if applicable.

Entity_Type_Definition_Source: Author defined

Attribute:

Attribute_Label: Table
Attribute_Definition: Name of the data table the field is found in.
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

The data tables in this data set include geology_40Ar39ArData_Alaska_Jones.csv and geology_40Ar39ArSummary_Alaska_Jones.csv.

Attribute:

Attribute_Label: Field
Attribute_Definition: Field name found in data table listed in Table.
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

The field names are single words or concatenated abbreviations that describe the contents of the field.

Attribute:

Attribute_Label: Description
Attribute_Definition: Brief description of the contents of the field
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Brief description of the contents of the field

Attribute:

Attribute_Label: Units
Attribute_Definition: The unit of measurement for applicable data fields
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Enumerated_Domain:

Enumerated_Domain_Value: %
Enumerated_Domain_Value_Definition: percent
Enumerated_Domain_Value_Definition_Source: Author defined

Attribute_Domain_Values:

Enumerated_Domain:

Enumerated_Domain_Value: Ma
Enumerated_Domain_Value_Definition: mega-annum or million years
Enumerated_Domain_Value_Definition_Source: Author defined

Attribute_Domain_Values:

Enumerated_Domain:

Enumerated_Domain_Value: mV
Enumerated_Domain_Value_Definition: millivolt
Enumerated_Domain_Value_Definition_Source: Author defined

Attribute_Domain_Values:

Enumerated_Domain:

Enumerated_Domain_Value: MW
Enumerated_Domain_Value_Definition: megawatt
Enumerated_Domain_Value_Definition_Source: Author defined

Attribute_Domain_Values:

Enumerated_Domain:

Enumerated_Domain_Value: n/a
Enumerated_Domain_Value_Definition: not applicable
Enumerated_Domain_Value_Definition_Source: Author defined

40Ar/39Ar Isotopic Data and Ages for Rocks from the Yukon-Tanana Upland of Eastern Alaska and the Northern Aleutian Range of South-Central Alaska

Metadata: