{'fraction_non_alphanumeric': 0.04279749478079332, 'fraction_numerical': 0.017745302713987474, 'mean_word_length': 4.543352601156069, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
K-Ar biotite and fission-track zircon ages of the Nisatai Dacite, Iwate Prefecture, Japan: A candidate for Tertiary age standard

K-Ar biotite and fission-track (FT) zircon ages were determined on the Nisatai Dacite (ND), Iwate Prefecture, Japan, to assess its suitability for a geologic age standard. The concentration of potassium and argon isotope ratios were determined on a biotite sample twice and three times, respectively, and yielded reproducible results within analytical errors. A K-Ar age was given as 21.0±0.3 (2 sigma) Ma. FT zircon ages were determined on two samples from different localities as 21.8±1.4 (2 sigma) and 23.9±1.4 Ma. The K-Ar age was obtained from an outcrop adjacent to that for the former FT age, with a good agreement between the two methods. The concordance in age, in conjunction with previous zircon FT length data, suggests a potential applicability of the ND to both the K-Ar and FT system calibration in Cenozoic time.