Calibration of GA1550 biotite standard for K/Ar and 40Ar/39Ar dating

Ian McDougall*, Peter Wellman

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    65 Citations (Scopus)

    Abstract

    The mineral separate GA1550 biotite has become an international standard for K/Ar and 40Ar/39Ar dating studies, although it was prepared as an intralaboratory standard at ANU to monitor tracer depletion from a gas pipette. It is one of a small number of samples that has been calibrated against 38Ar tracers, some of which had been mixed with known amounts of atmospheric argon, so that a so-called primary calibration has been performed. By measuring GA1550 biotite against additional tracers from the same batch we have determined the radiogenic argon content of this sample as 1.342 (±0.007)×10-9mol/g, and together with the measured K content of 7.645 (±0.050) weight percent, we derive a best estimate for the K/Ar age as 98.5±0.5Ma, where the error is derived from averaging the ages determined relative to the 38Ar tracer.

    Original languageEnglish
    Pages (from-to)19-25
    Number of pages7
    JournalChemical Geology
    Volume280
    Issue number1-2
    DOIs
    Publication statusPublished - 7 Jan 2011

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