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

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• 作者：Ian McDougall^a ; ^{Ian.McDougall@anu.edu.au} ; Peter Wellman^b
• 关键词：K/Ar geochronology ; Biotite standard ; Calibrations ; Mount Dromedary ; Australia
• 刊名：Chemical Geology
• 出版年：2011
• 出版时间：7 January 2011
• 年：2011
• 卷：280
• 期：1-2
• 页码：19-25
• 全文大小：659 K

文摘

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^− 9 mol/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 ± 0.5 Ma, where the error is derived from averaging the ages determined relative to the ³⁸Ar tracer.