Very low potassium analysis by flame photometry using ultra low blank chemical lines. An application of K-Ar method to ophiolites.

Itaya, Tetsumaru; Doi, Masako; Ohira, Takeshi

doi:10.2343/geochemj.30.31

Cited by 15 publications

(10 citation statements)

References 14 publications

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“…Potassium concentrations in the mixture of plagioclase and anorthoclase were determined by flame photometry using the method described by Nagao et al (1984), while those in olivine were determined with the low-K analytical method developed by Itaya et al (1996), using the newly designed and constructed ultra-low blank chemical line. Argon was analyzed at Okayama University of Science using a 15 cm-radius sector type mass spectrometer with a single-collector, utilizing isotope dilution and Argon-38 spike methods (Itaya et al, 1991).…”

Section: K-ar Analysismentioning

confidence: 99%

K-Ar ages of the Quaternary basalts in the Jeongok area, the central part of Korean Peninsula

Ryu

Oka

Yagi³

et al. 2011

Geosci J

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The Quaternary basalts along the Chugaryeong Fault zone in central part of the Korean Peninsula are composed of two stratigraphic units in the Jeongok area, calling the Chatan and Jeongok basalts. K-Ar analyses of the mixture of the finegrained plagioclase and anorthoclase from the 18 basalt samples were carried out to reveal the volcanic activity of the area. The results show that the Chatan and Jeongok basalts give a uniform age, giving the weighted average ages of 0.15 ± 0.01 and 0.51 ± 0.01 Ma, respectively. This reveals the age gap between the Chatan and Jeongok basalts was 360,000 years, providing a unique volcanic history for the Quaternary volcanism. The volcanism formed the two large amounts of alkali olivine basalt flows that are similar to each other in primitive chemical composition, phenocryst composition and viscosity with an interval of 360,000 years. The results also make a time constraint on the Jeongok Paleolithic Site where the Jeongok basalt occurs below the sediments containing the Paleolithic artifacts. The age (0.51 Ma) of the Jeongok basalt provides the lower limit for the age of Paleolithic artifacts. Olivine phenocrysts from both the Chatan and Jeongok basalts have significant amount of excess argon, giving apparent older ages on the whole rock K-Ar dating by previous researchers.

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Section: K-ar Analysismentioning

confidence: 99%

K-Ar ages of the Quaternary basalts in the Jeongok area, the central part of Korean Peninsula

Ryu

Oka

Yagi³

et al. 2011

Geosci J

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“…The rock samples were sent to the CGAEV for the Rb Sr analysis and the mineral samples to the VSEGEI for K Ar analyses. The K Ar analytical method at RINS has been reported by Nagao et al (1984) and Itaya et al (1991Itaya et al ( , 1996 and then is described below.…”

Section: Geochronology Laboratories and Their Analytical Methodsmentioning

confidence: 99%

Rb-Sr Isochron and K-Ar ages of igneous rocks from the Samnua Depression Zone in Northern Vietnam

Trung

Nuong

Itaya

2007

Journal of Mineralogical and Petrological Sciences

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The Samnua Depresion Zone (SNDZ) extends NW SE for more than 400 km from Northern Vietnam to Southwestern China. It represents the northern edge of the Indochina block and is separated from The groundmass fraction of the CBR yields an age of 1.9 Ma. Geochronological comparison and using fossil records suggest that the Rb Sr ages of Mesozoic igneous rocks provide apparent young age, a pseudo isochron age. The major igneous activity of the SNDZ took place during Late Permian Triassic time to form granitic and felsic volcanic rocks, which were related to the continental volcanic arc magmatism. Minor intraplate igneous activity occurred in the Paleogene. This suggests that the tectonic environment of the SNDZ changed from a convergent plate margin to a matured continental margin in the time span between the Triassic and Paleogene.

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“…Potassium concentrations in the biotite, hornblende and groundmass fractions were determined by flame photometry using the method described by Nagao et al (1984), whereas those in clinopyroxene and plagioclase were determined with the low-K analytical method developed by Itaya, Doi & Ohira (1996), using the newly designed and constructed ultra-low blank chemical line mentioned above. Multiple runs of a standard (JP-1, 0.00387 wt %; Itaya, Doi & Ohira, 1996) indicate that the error of the potassium analyses is less than 5 %.…”

Section: K-ar Age Determinationmentioning

confidence: 99%

“…The flame photometric method developed by Itaya, Doi & Ohira (1996) overcomes the difficulty of analysing rocks and minerals with very low potassium contents. They applied their method to igneous and metamorphic hornblende from ophiolite complexes, and to coexisting hornblende and clinopyroxene from Cretaceous volcanic rocks.…”

Section: A Implications For K-ar Dating Of Clinopyroxenementioning

confidence: 99%

“…In the Susa area of this district, the Yamashima andesites occur in close association with the Koyama gabbros (Figs 1, 2). Itaya, Doi & Ohira (1996) developed a flame photometric method to precisely determine K contents in minerals and rocks at very low concentrations. attempted to apply K-Ar chronology to both the * Author for correspondence: imaoka@yamaguchi-u.ac.jp volcanic and plutonic suites to unravel the formation process of the Susa complex, and to confirm the genetic link between the Koyama gabbros and the Yamashima andesites.…”

Section: Introductionmentioning

confidence: 99%

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K–Ar geochronology of a middle Miocene submarine volcano-plutonic complex in southwest Japan

Imaoka

Itaya

2004

Geol. Mag.

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A volcano-plutonic complex in the Susa area, southwest Japan, consists of the Yamashima andesites, the Koyama gabbros and syn-plutonic porphyrite dykes derived from a common basaltic andesite magma. The complex is closely associated with middle Miocene turbidite deposits. The Yamashima andesites are composed mainly of basaltic andesite feeder dykes, massive submarine lavas with hyaloclastites, and their reworked deposits. The lavas and deposits immediately overlie turbidite deposits, indicating submarine volcanic activity. The Koyama gabbros formed hornfels by contact metamorphism of the surrounding turbidites and andesites. Highly purified clinopyroxene and plagioclase mineral separates from the Yamashima andesites were dated by a K-Ar method using an ultra-low blank K analysis procedure. Ages obtained from duplicate analyses are 16.5 ± 1.5, 15.2 ± 1.4, 15.8 ± 1.7, and 16.5 ± 2.0 Ma for clinopyroxene, and 14.2 ± 0.8, 15.2 ± 0.9, and 15.6 ± 0.9 Ma for plagioclase. The clinopyroxene and plagioclase data define a mineral isochron age of 14.7 ± 0.9 (1σ ) Ma with an initial 40 Ar/ 36 Ar ratio of 297.3 ± 2.4 (1σ ), suggesting that clinopyroxene has no excess argon and can be reliably dated by K-Ar. Most of the groundmass ages are considerably younger (12.1-14.6) than the isochron age, perhaps due to argon loss during alteration. The gabbros give ages of 14.2 ± 0.3 and 14.1 ± 0.3 Ma for biotite, and 13.7 ± 0.3 and 13.7 ± 0.7 Ma for green hornblende. The porphyrite dyke yields an age of 12.5 ± 0.3 Ma for the groundmass, and the pelitic hornfels gives a biotite age of 14.8 ± 0.3 Ma. Our new K-Ar ages, together with previous studies, show that a series of geological events took place in the Susa area between 16 and 13 Ma. Conglomerates and sandstones were deposited in the beginning of marine transgression. Subsequent abrupt deepening led to deposition of a thick black shale unit, turbidite deposits and large-scale submarine channel-fill deposits. Coeval igneous activity formed the volcano-plutonic complex. The magmato-tectonic event was synchronous with the opening of the Japan Sea and the associated clockwise rotation of the southwest Japan arc sliver, recording a unique tectonic setting.

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Very low potassium analysis by flame photometry using ultra low blank chemical lines. An application of K-Ar method to ophiolites.

Cited by 15 publications

References 14 publications

K-Ar ages of the Quaternary basalts in the Jeongok area, the central part of Korean Peninsula

K-Ar ages of the Quaternary basalts in the Jeongok area, the central part of Korean Peninsula

Rb-Sr Isochron and K-Ar ages of igneous rocks from the Samnua Depression Zone in Northern Vietnam

K–Ar geochronology of a middle Miocene submarine volcano-plutonic complex in southwest Japan

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