Locations_Results_AnalyticalData coordinates of sample locations, 40Ar/39Ar age summary, analytical data (Tables 1, 2, 3)
Layer, P.W., and Solie, D.N., 200811, 40Ar/39Ar ages from the Selawik A-2, A-3 and A-4 and Candle B-5 quadrangles, Alaska: Raw Data File RDF 2008-5, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys, Fairbanks, Alaska - USA.Online Links:
This is a Point data set.
Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest 1
Ordinates (y-coordinates) are specified to the nearest 1
Planar coordinates are specified in meters
The horizontal datum used is North American Datum of 1927.
The ellipsoid used is Clarke 1866.
The semi-major axis of the ellipsoid used is 6378206.4.
The flattening of the ellipsoid used is 1/294.978698.
Sample numbers are unique identifiers derived from the last two digits of the year the sample was collected, initials of the geologist's name who collected it, and the consecutively numbered station location. If more than one sample was collected from the station location, each is assigned a letter (a, b, c, etc) designator as well.
| Range of values | |
|---|---|
| Minimum: | 394311 |
| Maximum: | 463220 |
| Units: | m |
| Range of values | |
|---|---|
| Minimum: | 7255163 |
| Maximum: | 7339612 |
| Units: | m |
| Range of values | |
|---|---|
| Minimum: | 65.40369 |
| Maximum: | 66.17045 |
| Units: | decimal degree |
| Range of values | |
|---|---|
| Minimum: | 159.81421 |
| Maximum: | 161.57441 |
| Units: | decimal degree |
Material used for dating. Includes Bio (biotite) or Hbd (hornblende).
| Range of values | |
|---|---|
| Minimum: | 98.8+-0.7 |
| Maximum: | 107.4+-0.8 |
| Units: | Ma |
| Range of values | |
|---|---|
| Minimum: | 100.4+-3.7 |
| Maximum: | 107.1+-0.8 |
| Units: | Ma |
# of fractions, % 39Ar released, MSWD for each sample
Sample numbers are unique identifiers derived from the last two digits of the year the sample was collected, initials of the geologist's name who collected it, and the consecutively numbered station location. If more than one sample was collected from the station location, each is assigned a letter (a, b, c, etc) designator as well.
rock type, either a type of plutonic rock or a generalized metamorphic rock
| Range of values | |
|---|---|
| Minimum: | 0.0605 |
| Maximum: | 0.3588 |
| Units: | grams |
| Range of values | |
|---|---|
| Minimum: | 9 |
| Maximum: | 12 |
| Units: | each |
| Range of values | |
|---|---|
| Minimum: | 0.72 |
| Maximum: | 7.15 |
| Units: | weight % |
| Range of values | |
|---|---|
| Minimum: | 0.64 |
| Maximum: | 15.37 |
| Units: | weight % |
| Range of values | |
|---|---|
| Minimum: | 101.6+-0.8 |
| Maximum: | 107.1+-0.8 |
| Units: | Ma |
| Range of values | |
|---|---|
| Minimum: | 400 |
| Maximum: | 1600 |
| Units: | Degrees C |
| Range of values | |
|---|---|
| Minimum: | 0.0000 |
| Maximum: | 1.0000 |
| Range of values | |
|---|---|
| Minimum: | 0.0001 |
| Maximum: | 634.0000 |
| Range of values | |
|---|---|
| Minimum: | 0.0000 |
| Maximum: | 509.0000 |
| Range of values | |
|---|---|
| Minimum: | 0.00000 |
| Maximum: | 23.00000 |
| Range of values | |
|---|---|
| Minimum: | 0.0000 |
| Maximum: | 3.2000 |
| Range of values | |
|---|---|
| Minimum: | 0.0 |
| Maximum: | 150.0 |
| Range of values | |
|---|---|
| Minimum: | 0.0000 |
| Maximum: | 43.0000 |
| Range of values | |
|---|---|
| Minimum: | 0.00000 |
| Maximum: | 0.15000 |
| Range of values | |
|---|---|
| Minimum: | 0.0000 |
| Maximum: | 12.0000 |
| Range of values | |
|---|---|
| Minimum: | 0.0 |
| Maximum: | 185.0 |
| Units: | Ma |
| Range of values | |
|---|---|
| Minimum: | 0.2 |
| Maximum: | 3167.0 |
| Units: | Ma |
This research was supported by State funding to the Alaska Division of Geological & Geophysical Surveys. Additional Acknowledgments: members of the 1991 DGGS field teams: Thomas K. Bundtzen, Rainer J. Newberry, Greg M. Laird, Ellen E. Harris, Milt A. Wiltse, Jeffrey T. Kline, Thomas E. Smith, Shirley A. Liss and Karen H. Clautice. Review of draft manuscript by D.J. Szumigala.
(907) 451-5029 (voice)
(907) 451-5050 (FAX)
dggspubs@alaska.gov
In 1991, the Alaska Division of Geological & Geophysical Surveys (DGGS) conducted helicopter-supported field work in west-central Alaska as part a state-wide project to review selected areas of federal land that were eligible at the time for selection by Alaska to become state land. DGGS’s role in the project was to evaluate mineral resource potential in the eligible units of land by acquiring data to outline permissive mineral terranes and to define mineral deposit types that could occur in each land selection unit (DGGS Staff, 1992). The data in this report resulted from investigations in the Selawik Hills and Granite Mountain areas as part of the land selection project. Geochemical and major oxide data (Solie and others, 1993a) and electron microprobe data (Solie and others, 1993b) were previously published. A brief discussion of our 40Ar/39Ar results from the Selawik Hills was presented at a Geological Society of America meeting (Solie and Layer, 1993). The purpose of this DGGS Raw Data File (RDF) is to present all our 40Ar/39Ar results from the Selawik Hills and Granite Mountain and make them available for use.
Lanphere, M.A., Dalrymple, G.B., Fleck, R.J., and Pringle, M.S., 1990, Intercalibration of mineral standards for K/Ar and 40Ar/39Ar age measurements: EOS Transactions of the American Geophysical Union v. 71.
McDougall, Ian, and Harrison, T.M., 1999, Geochronology and Thermochronology by the 40Ar/39Ar method: Oxford University Press, Oxford.
Samson, S.D., and Alexander, E.C., 1987, Calibration of the interlaboratory 40Ar/39Ar dating standard, MMhb-1: Chemical Geology v. 66.
Steiger, R.H., and Jager, E, 1977, Subcommission on geochronology: convention on the use of decay constants in geo- and cosmochronology: Earth and Planetary Science Letters v.36.
Solie, D.N., Harris, E.E., Bundtzen, T.K., Wiltse, M.A., Newberry, R.J., Kline, J.T., and Smith, T.E., 199303, Land Selection Unit 16 (Selawik, Candle, Norton Bay, Unalakleet, Kateel River, and Nulate quadrangles): references,DGGS sample locations, geochemical and major oxide data: Public Data File PDF 93-16a, Alaska Division of Geological & Geophysical Surveys, Fairbanks AK.
Solie, D.N., Severin, K.P., and Lear, K.G., 199305, Electron microprobe data from Selawik Hills and Granite Mountain plutonic rocks, western Alaska: Public Data File PDF 93-16b, Alaska Division of Geological & Geophysical Surveys, Fairbanks AK.
Solie, D.N., and Layer, P.W., 1993, Evidence of synmagmatic foliation in the Selawik Hills, NW Alaska, based on 40Ar/39Ar age determinations: Geological Society of America Abstracts with Programs v.25, no.5.
Data sources used in this process:
The irradiated samples were step-heated on-line in a Modifications Ltd. low-blank furnace. Temperature control was better than 5 degrees and a maximum temperature in excess of 1600o C was achievable to ensure complete sample fusion. The extracted argon was purified in a two-stage process using a liquid nitrogen cold finger and two SAES Zr-Al getters. Prior to measurement of the Ar, the gas was collected on an activated charcoal finger. The purified Ar gas was measured using a Nuclide 6-60-SGA 15 cm mass spectrometer. The sensitivity of the spectrometer is 6.5 x 10-15 mol/mV and system noise is generally around 0.02 mV. System blanks are generally better than 1 X 10-14 mol for 40Ar. Argon isotopic measurements for both samples and standards were corrected for the system blanks, for decay of 37Ar and 39Ar, and for reactor-induced isotopic interferences. Ages were calculated using the equations and corrections from McDougall and Harrison (1999) and the constants from Steiger and Jaeger (1977). All errors on analyses are reported at the 1-sigma level.
For each mass spectrometer analysis, five Ar isotope abundances are measured. 36Ar is used to determine the amount of atmospheric or initial Ar in the sample, 37Ar provides an estimation of the Ca content in the mineral, 38Ar provides an estimation of the Cl content, 39Ar reflects the K content and 40Ar is a mixture of initial and radiogenic Ar. The age of the sample is proportional to the ratio of the amount of radiogenic 40Ar to the amount of 39Ar produced by neutron bombardment from 40K.
Data sources used in this process:
All field locations were visually determined by the geologists in the field and recorded on a 1:63,360 topographic map. Coordinates were digitized visually from the field maps. DGGS submitted eight rock samples to the UAF Geochronology Laboratory for 40Ar/39Ar dating; three were collected from Granite Mountain in the Candle B-5 quadrangle and four were collected from the Selawik Hills in the Selawik quadrangle. Major oxide and selected trace element analyses for some of the samples are included in Solie and others (1993a). Separates for 40Ar/39Ar dating were prepared to >99.5 percent purity (visual inspection) using standard heavy liquid and magnetic separation techniques followed by hand-picking under a binocular microscope. Thin section examination of the samples prior to crushing indicated that the chosen minerals were free from alteration and sufficiently coarse-grained for mechanical separation. For all minerals, grains in the size range of 250 - 500 microns were used. For each sample, ~50-80 mg of biotite or 250-350 mg of hornblende or ‘whole rock’ (phenocryst-free groundmass) was packaged in an aluminum foil tube and irradiated in position 5C at the McMaster University nuclear reactor, in Hamilton, Ontario. Approximately 20 samples were irradiated at a time. Six packages containing ~20 mg of the standard mineral mmhb-1 (Samson and Alexander, 1987) with an age of 513.9 Ma (Lanphere and others, 1990) were also irradiated with the samples to determine the irradiation parameter (J) and the flux gradient in the reactor. Samples and standards were analyzed 45 to 90 days after irradiation. The irradiated samples were step-heated on-line in a Modifications Ltd. low-blank furnace. Temperature control was better than 5 degrees and a maximum temperature in excess of 1600o C was achievable to ensure complete sample fusion. The extracted argon was purified in a two-stage process using a liquid nitrogen cold finger and two SAES Zr-Al getters. Prior to measurement of the Ar, the gas was collected on an activated charcoal finger. The purified Ar gas was measured using a Nuclide 6-60-SGA 15 cm mass spectrometer. The sensitivity of the spectrometer is 6.5 x 10-15 mol/mV and system noise is generally around 0.02 mV. System blanks are generally better than 1 X 10-14 mol for 40Ar. Argon isotopic measurements for both samples and standards were corrected for the system blanks, for decay of 37Ar and 39Ar, and for reactor-induced isotopic interferences. Ages were calculated using the equations and corrections from McDougall and Harrison (1999) and the constants from Steiger and Jaeger (1977). Age, Ca/K and Cl/K spectra plots are shown in figure 3, and analytical age data are shown in Tables 2 and 3. All errors on analyses are reported at the 1-sigma level. For each mass spectrometer analysis, five Ar isotope abundances are measured. 36Ar is used to determine the amount of atmospheric or initial Ar in the sample, 37Ar provides an estimation of the Ca content in the mineral, 38Ar provides an estimation of the Cl content, 39Ar reflects the K content and 40Ar is a mixture of initial and radiogenic Ar. The age of the sample is proportional to the ratio of the amount of radiogenic 40Ar to the amount of 39Ar produced by neutron bombardment from 40K. All samples were dated by the 40Ar/39Ar step-heating method. In this method, a sample is heated to progressively higher temperatures in a double-vacuum resistance-heated furnace, and the argon isotopes are measured and age determined for each step (fraction). The integrated age is the age given by the total gas measured in all fractions and is equivalent to a potassium-argon (K-Ar) age. The fractions are commonly plotted on an age spectrum plot for analysis. A spectrum provides a plateau age if three or more consecutive gas fractions represent at least 50% of the total gas release and are within two standard deviations of each other (Mean Square Weighted Deviation less than ~2.5). If the fractions do not meet the criteria for a plateau due to intrafraction scatter in ages, then a weighted mean age of ‘plateau-like’ fractions, with each fraction weighted by the volume of 39Ar released, is calculated.
Sample locations were determined visually by geologist in the field, using a brunton compass and altimeter and topographic map. Locations were then digitized visually from the field maps using ArcGIS v9.2.
This dataset includes all of the samples submitted for 40Ar/39Ar age date analyses from the Selawik and Candle quadrangle which were collected by DGGS during the summer of 1991. Hand samples and thin sections are no longer available for the samples dated. The brief sample descriptions in text are compiled from field notes and some preliminary petrographic notes from 1991.
No topologic relationships are present in the data.
Are there legal restrictions on access or use of the data?
- Access_Constraints:
- This report 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. 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.
907-451-5020 (voice)
907-451-5050 (FAX)
dggspubs@alaska.gov
Raw-Data File
The State of Alaska makes no express or implied warranties (including warranties of merchantability and fitness) with respect to the character, function, or capabilities of the electronic services 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, any failure thereof, or otherwise, and in no event will the State of Alaska's liability to the requester or anyone else exceed the fee paid for the electronic service or product.
Current publication is available on paper. To purchase this or other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard.
Printed publication can be purchased (contact information below) plus shipping if mailed.
Two weeks unless special arrangements are made and an express fee is paid.
| Data format: | PDF (version 1.6) |
|---|---|
| Network links: |
<http://www.dggs.alaska.gov/pubs/> |
Digital files on CD-ROM are available (contact information below). Scanned images of these products may be viewed online or downloaded for free from the DGGS Web site.
Order by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard.
907-451-5039 (voice)
907-451-5050 (FAX)
dggspubs@alaska.gov