Argon 39 argon 40 dating dating list facebook
Illite crystallization ages from the NPRA (National Petroleum Reserve in Alaska) range between 205 and 225 Ma.These ages are older than depositional ages and therefore suggest that this illite was transported from outside the Colville basin, perhaps from the Brooks Range.This allows the measurement of a larger dynamic range of Ar ion beam signal on much smaller (and thus likely purer) and younger sample aliquots.Their second advantage is the ability to measure the 36Ar on the CDD multiplier while other masses are measured on the faraday detectors, resulting in analytical precision one order of magnitude better than with previous generation instruments.Their third advantage is much faster sample analysis (i.e., 30-35 analyses/day compared to the current 10-12 analyses/day for single collector instruments.A new dedicated low volume Noble Gas extraction line capable of collecting and cleaning the gas extracted from a variety of samples, using a Photon Machine CO2 laser capable of delivering a homogenous laser beam of up to 6mm wide, is attached to the ARGUS VI mass spectrometer.Shale samples from north of the thrust yield staircase age spectra indicative of a detrital illite component, and older retention ages (233-391 Ma).
40 Ar/39 Ar age spectra from the Colville basin, North Slope, Alaska, illites are generally dominated by detrital illite, yielding high temperature step-heat ages up to 475 Ma.The bottom, green spectrum is what we would expect to see if we had an ideal sample that has no excess-Ar, and the top, blue spectrum is what we might expect if the sample contained excess-Ar in fluid inclusions.Both of these “experiments” involved 7 heating steps where the temperature increased for each step and the gas released from each step was analysed.X-ray diffraction of the Colville basin samples indicates the presence of multiple clay phases, including detrital and neoformed illite.This complex mineralogy precluded estimating when the host shales were within the oil generation window.
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Ca/K) information can be obtained from each sample.