K-Ar dating of lavas from Zao volcano, north-eastern Japan.

Takaoka, N.; Konno, Kouichi; Ôba, Yoshio; Konda, Tadashi

doi:10.5575/geosoc.95.157

Cited by 33 publications

(15 citation statements)

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“…They also suggested a possibility that lavas in the Central Zao may have recorded short events within the.Brunhes chron such as Biwa event. TAKAOKA et al (1989), (A: single data, B: mean and standard deviation were calculated in this study from multiple data, C: rough estimate due to either inconsistency or large error in the K-Ar datings), D: O1A et al (1990D: O1A et al ( ), E: TAKAOKA et al (1988, N: number of paleomagnetic samples collected as core(c) or hand samples(h) in this study. ages are included in the table.…”

Section: Geology and Samplesmentioning

confidence: 96%

“…After the period of inactivity spanning several hundreds of thousand of years, the second stage of the activity initiated at about 0.5 Ma and stopped around 0.2 Ma (OBA et al, 1990;NUMAKUNAI et al, 1992). TAKAOKA et al (1989) reported an age of 0.07 Ma for Sumikawa Lava (Z010), but subsequent study by OBA et al (1990) concluded conflicting ages. They reported that one sample from the same site yields an age of 0.26±0.02 Ma and three samples from the adjacent lavas have ages between 0.26 and 0.31 Ma.…”

Section: Geology and Samplesmentioning

confidence: 98%

“…1). The formation history of the Zao Volcano Group was studied by TAKAOKA et al (1989) by means of K-Ar method. According to their results, Ryuzan Volcano erupted basalt and andesite lavas between 0.94 to 1.13 Ma, and has been dormant since then.…”

Section: Geology and Samplesmentioning

confidence: 99%

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Paleomagnetic Study of Pleistocene Lavas and Dikes of the Zao Volcano Group, Japan.

Otake

Tanaka

Kono

et al. 1993

J. geomagn. geoelec

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Paleomagnetic studies, both directions and intensities, were made on lavas and dikes of Pleistocene age collected at the Zao Volcano Group, Japan. All the rock units collected have radiometric ages obtained by K-Ar method which cover the last one million years. Among 16 paleodirections obtained after cleaning by alternating field and thermal demagnetizations, eleven belong to the Brunhes chron, four to the Matuyama chron and one probably to the Jaramillo subchron. Angular standard deviation calculated from eleven sites of Brunhes chron was 11.9° with upper and lower 95% confidence limits of 16.8° and 9.2° respectively. This value is not inconsistent with the result from 113 poles in the Brunhes chron for Central Japan, although the confidence interval of our result is too large to assess any regional difference in paleosecular variation.Paleointensity experiment by the Thelliers' method was applied to a total of 70 specimens from nine cooling units. Among them, 31 specimens gave successful results and four and two paleointensities were obtained for the Brunhes and Matuyama chrons, respectively. Some correlations were found between the success rate of paleointensity experiment and reproducibility of the continuous measurements of magnetic susceptibility versus temperature. Such measurement of susceptibility and repeating it stepwisely by increasing the maximum temperature attained is proposed as a preceding technique to select suitable samples for thermal demagnetization and the Thelliers' experiment.

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Section: Geology and Samplesmentioning

confidence: 96%

Section: Geology and Samplesmentioning

confidence: 98%

See 1 more Smart Citation

Paleomagnetic Study of Pleistocene Lavas and Dikes of the Zao Volcano Group, Japan.

Otake

Tanaka

Kono

et al. 1993

J. geomagn. geoelec

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“…Radiogenic 40 Ar was determined with a VG3600 mass spectrometer by the unspiked sensitivity method. The initial 40 Ar/ 36 Ar ratio was corrected for the natural mass fractionation by a mass fractionation correction procedure (MFCP) (Itaya and Nagao, 1988;Takaoka et al, 1989;Matsumoto et al, 1989a) since the studies on historical lavas indicated that natural mass fractionation of initial Ar isotopic ratios should be corrected (Matsumoto et al, 1989b;Ozawa et al, 2006). Details of the K-Ar dating method is described in Mochizuki et al (2004a).…”

Section: K-ar Dating Methodsmentioning

confidence: 99%

Further K-Ar dating and paleomagnetic study of the Auckland geomagnetic excursions

et al. 2007

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Three different excursional paleomagnetic directions were reported from eight volcanoes of the Auckland volcanic field in New Zealand: north-down (ND) directions obtained from five volcanoes, west-up (WU) from two volcanoes, and south-up (SU) from one volcano. K-Ar ages have been reported for two of these volcanoes: 27±5 (1σ ) ka for the Wiri volcano of the ND group and 55±5 ka for the Hampton Park volcano of the WU group. In the present study, we have carried out further K-Ar age determinations on three other volcanoes and obtained reliable ages for two of them: 30±5 ka for the Puketutu volcano of the ND group and 50±6 ka for the McLennan Hills volcano of the SU group. The age of Puketutu agrees well with that of Wiri, and these two ages give a weighted mean age of 29±3 (1σ ) ka for the ND group. The age of the ND group is distinguishable from those of the SU and WU groups at the 2σ level, confirming that excursions occurred at two different times separated by a few tens of thousands of years. The age of the SU group is indistinguishable from that of the WU group, and a weighted mean age of 53±4 ka can be calculated for this combined group (SU-WU group). The age of the ND group and that of the SU-WU group are distinguishable from the latest age estimate of the Laschamp excursion. Overall, these age data from volcanic rocks show that at least three excursions occurred between approximately 30 and 60 ka. These three excursions are likely to be confined in the weak dipole interval of 20-70 ka, and all of these excursions yield particularly low virtual dipole moments (VDMs) of 2×10 22 A m 2 or less. Since it is suggested that the larger virtual geomagnetic pole (VGP) deviations from the geographic pole are related to the lower VDMs, the excursional fields possibly have resulted from a significantly reduced dipole field and comparable non-dipole components.

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“…The isotope analyses of Ar were performed with a VG Isotopes 1200C mass spectrometer. We employed the peak height comparison method (Takaoka et al, 1989), wherein the concentration of 40Ar in sample is obtained by comparing peak intensities with the known amount of air standard. The laboratory procedures of Ar analysis adopted in this study were documented by Matsumoto et al (1989).…”

Section: K-ar Datingmentioning

confidence: 99%

K-Ar biotite and fission-track zircon ages of the Nisatai Dacite, Iwate Prefecture, Japan: A candidate for Tertiary age standard.

et al. 1995

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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.

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K-Ar dating of lavas from Zao volcano, north-eastern Japan.

Cited by 33 publications

References 0 publications

Paleomagnetic Study of Pleistocene Lavas and Dikes of the Zao Volcano Group, Japan.

Paleomagnetic Study of Pleistocene Lavas and Dikes of the Zao Volcano Group, Japan.

Further K-Ar dating and paleomagnetic study of the Auckland geomagnetic excursions

K-Ar biotite and fission-track zircon ages of the Nisatai Dacite, Iwate Prefecture, Japan: A candidate for Tertiary age standard.

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