Folders: ROOT > ScienceBase Catalog > ReSciColl Archive > Alaska Division of Geological & Geophysical Surveys > Collection of radiometric age data from Alaska ( Show all descendants )
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ROOT _ScienceBase Catalog __ReSciColl Archive ___Alaska Division of Geological & Geophysical Surveys ____Collection of radiometric age data from Alaska Filters
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At the University of Wisconsin Rare Gas Geochronology Laboratory, the groundmass packets and mini-cores were ncrementally heated in a double-vacuum resistance furnace attached to a 300 cm3 gas clean-up line. Prior to each incremental-heating experiment, samples were heated to 500-675 �C and pumped to remove potentially large amounts of atmospheric argon and water (Baksi, 1974). Fully automated experiments consisted of 4-10 steps from 675-1450 �C; each step included a 2 min increase to the desired temperature that was maintained for 10-15 min. During the heating time, and for an additional 5-8 min afterward, the sample gas was exposed to three SAES C50 Zr-Al getters. Isotopic measurements and data reduction followed...
Categories: Physical Item;
Tags: Age date
At the University of Wisconsin Rare Gas Geochronology Laboratory, the groundmass packets and mini-cores were ncrementally heated in a double-vacuum resistance furnace attached to a 300 cm3 gas clean-up line. Prior to each incremental-heating experiment, samples were heated to 500-675 �C and pumped to remove potentially large amounts of atmospheric argon and water (Baksi, 1974). Fully automated experiments consisted of 4-10 steps from 675-1450 �C; each step included a 2 min increase to the desired temperature that was maintained for 10-15 min. During the heating time, and for an additional 5-8 min afterward, the sample gas was exposed to three SAES C50 Zr-Al getters. Isotopic measurements and data reduction followed...
Categories: Physical Item;
Tags: Age date
At the University of Wisconsin Rare Gas Geochronology Laboratory, the groundmass packets and mini-cores were ncrementally heated in a double-vacuum resistance furnace attached to a 300 cm3 gas clean-up line. Prior to each incremental-heating experiment, samples were heated to 500-675 �C and pumped to remove potentially large amounts of atmospheric argon and water (Baksi, 1974). Fully automated experiments consisted of 4-10 steps from 675-1450 �C; each step included a 2 min increase to the desired temperature that was maintained for 10-15 min. During the heating time, and for an additional 5-8 min afterward, the sample gas was exposed to three SAES C50 Zr-Al getters. Isotopic measurements and data reduction followed...
Categories: Physical Item;
Tags: Age date
Laser-fusion analyses were performed using a Spectra Physics 2016 continuous argon-ion laser to fuse one or several grains per analysis. Isotopic abundances for both step-heating and laser-fusion analyses were calculated by linear extrapolation to inlet time of peak heights above background during sex serial scans.
Categories: Physical Item;
Tags: Age date
40Ar/39Ar step-heating was performed. Individual samples consisted of up to several grains from each respective irradiated sample, loaded into 2 mm-diameter holes in a copper tray, which was then loaded in an ultra-high vacuum line. Samples were step-heated using a 6-watt argon-ion laser. Argon was purfied using a liquid nitrogen cold trap and a SAES Zr-Al getter aat 400C. Argon isotopes were measured using a VG-3600 mass spectrometer, with corrections for system blanks, decay of 39Ar and 37 Ar, and reactor-induced interferences.
Categories: Physical Item;
Tags: Age date
Laser dating system was used to step-heat the samples and the monitors, using a 6 W argon-ion laser to step-heat small chips of melt rock following the techniques in Layer et al. (1987). During the heating process, a liquid N cold finger and a Zr-Al getter at 400 degree C purified the gas, which was then measured with a VG3600 mass spectrometer. The Ar isotopes measured were corrected from post irradiation decay of 37Ar and 39Ar, system blank, mass discremination, as well as Ca, K, and Cl interference reactions following procedures of outlined in McDougall and Harrison (1988). The weighted mean of the results obtained on the monitor samples was used on the ensuing calculations for their corresponding set of samples....
Categories: Physical Item;
Tags: Age date
Samples are step-heated in a Modifications Ltd. Low-bland furnace connected on-line to the mass spectrometer. Temperature control is accurate to 1C. Extracted argon is purified in a two-stage process. First stage exposes the ssample to a liquid nitrogen cold finger and a Ti furnace at 700C for 20 minutes. Argon is then drawn onto activated charcoal for 20 minutes. Argon is then released from the charcoal and further purified using a SAES ST101 getter for 10 minutes. Purifiec argon isotopes are then measured using a Nuclide 6-60-SGA 15 cm mass spectrometer. Sensitivity of the instrument is 6.5 x 10^-15 mol/mV and system noise is generall around 0.02 mV.
Categories: Physical Item;
Tags: Age date
The monitors were fused, and samples heated, using a 6 watt argon-ion laser following the technique described in York et al. (1981) and Layer et al. (1987). Argon purification was achieved using a liquid nitrogen cold trap and a SAES Zr-Al getter at 400C. The samples were then analyzed in a VG-3600 mass spectrometer. Argon isotopes measured were corrected for system blank and mass discrimination, as well as calcium, potassiou and chlorine interference reactions following procedures outlined in McDougall and Harrision (1999).
Categories: Physical Item;
Tags: Age date
Samples are step-heated in a Modifications Ltd. Low-bland furnace connected on-line to the mass spectrometer. Temperature control is accurate to 1C. Extracted argon is purified in a two-stage process. First stage exposes the ssample to a liquid nitrogen cold finger and a Ti furnace at 700C for 20 minutes. Argon is then drawn onto activated charcoal for 20 minutes. Argon is then released from the charcoal and further purified using a SAES ST101 getter for 10 minutes. Purifiec argon isotopes are then measured using a Nuclide 6-60-SGA 15 cm mass spectrometer. Sensitivity of the instrument is 6.5 x 10^-15 mol/mV and system noise is generall around 0.02 mV.
Categories: Physical Item;
Tags: Age date
The monitors were fused, and samples heated, using a 6 watt argon-ion laser following the technique described in York et al. (1981) and Layer et al. (1987). Argon purification was achieved using a liquid nitrogen cold trap and a SAES Zr-Al getter at 400C. The samples were then analyzed in a VG-3600 mass spectrometer. Argon isotopes measured were corrected for system blank and mass discrimination, as well as calcium, potassiou and chlorine interference reactions following procedures outlined in McDougall and Harrision (1999).
Categories: Physical Item;
Tags: Age date
Step heating analyses were performed using a VG3600 mass spectrometer system equipped with a 6 Watt argon-ion laser. Samples were heated for 30 seconds at the indicated laser power.
Categories: Physical Item;
Tags: Age date
After irradiation, the mineral separates were analyzed by step heating, using a 6-watt argon-ion laser, as described in Layer and others (1987). On average, 12-16 fractions were collected for each sample. Standards were included with each set of unknowns to nomitor the neutron flux. Each gas fraction was analyzed for Ar isotopic ratios in a VG-3600 mass spectrometer. The argon isotopes measured were corrected fro system blank and mass discrimination, as well as Ca, K, and Cl interference. Where 3 or more consecutive heating steps yielded the same age (+ or (-) 1 sigma), which accounted for more than 50% of the released Ar, the weighted average of these steps was calculaated as the
Categories: Physical Item;
Tags: Age date
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