Japan Geoscience Union Meeting 2021

Presentation information

[J] Oral

S (Solid Earth Sciences ) » S-GL Geology

[S-GL22] Geochronology and Isotope Geology

Fri. Jun 4, 2021 1:45 PM - 3:15 PM Ch.23 (Zoom Room 23)

convener:Takahiro Tagami(Graduate School of Science, Kyoto University), Yuji Sano(Division of Ocean and Earth Systems, Atmosphere and Ocean Research Institute, University of Tokyo), Chairperson:Takahiro Tagami(Graduate School of Science, Kyoto University), Yuji Sano(Center for Advanced Marine Core Research, Kochi University)

1:45 PM - 2:15 PM

[SGL22-01] Inter-method comparison study between 40Ar/39Ar and unspiked K-Ar method for some young volcanic rocks

★Invited Papers

*Seiko Yamasaki1, Daniel P. Miggins2, Anthony A.P. Koppers2 (1.Geological Survey of Japan, Advanced Industrial Science and Technology, 2.Oregon State University)

Keywords:Ar/Ar dating, unspiked K-Ar dating

Recent 40Ar/36Ar and unspiked K-Ar studies have been successfully applied toward younger and younger samples. The unspiked K-Ar method enables the correction for the mass fractionated initial 40Ar/36Ar ratios to yield more accurate ages. In the 40Ar/39Ar method, initial 40Ar/36Ar ratios can be assessed by the use of an inverse isochron plot, resulting in higher precisions.

We conducted inter-method comparison between 40Ar/39Ar and unspiked K-Ar dating method for some young volcanic rocks. The age results by both methods agree within errors and consistent with stratigraphic relationships, as well as concordant with reported conventional K-Ar, Thermo Luminescence, Fission Track and 14C ages. Some uncorrected ages show negative ages in both methods, but for all corrected age spectra we obtained positive ages. The calculated age differences between corrected and uncorrected ages are up to ~100 ka. We conclude that the initial argon correction is effective in dating younger samples, providing more robust ages for Quaternary samples