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 language | English |
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Pages (from-to) | 19-25 |
Number of pages | 7 |
Journal | Chemical Geology |
Volume | 280 |
Issue number | 1-2 |
DOIs | |
Publication status | Published - 7 Jan 2011 |