Argon isotope analysis by a newly developed mass spectrometric system for K-Ar dating.

Itaya, Tetsumaru; Nagao, Keisuke; Inoue, Kensaku; Honjou, Yoshiki; Okada, Toshinori; Ogata, Atsumi

doi:10.2465/minerj.15.203

Cited by 244 publications

(126 citation statements)

References 18 publications

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“…Hamilton (1937) Kear ( Table 2 Chronological database for Little Barrier Island. All K-Ar analyses were completed at Okayama University of Science (Takagi 1995); sample preparation and analytical techniques followed Briggs et al (1989) and Itaya et al (1991). Samples marked with an asterisk were collected by B. Hayward and their ages succinctly noted in Isaac et al (1994).…”

Section: Haowhenua Formationmentioning

confidence: 99%

Geology, petrology, and petrogenesis of Little Barrier Island, Hauraki Gulf, New Zealand

Lindsay

Worthington

Smith

et al. 1999

New Zealand Journal of Geology and Geophysics

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Little Barrier Island is the emergent part of a large, isolated, dacite-rhyodacite volcano in the active Hauraki Rift, 80 km northeast of Auckland. Two volcanic episodes are recognised: Waimaomao Formation was emplaced as a rhyodacite dome at 3 Ma, whereas the more extensive dacitic lavas of Haowhenua Formation were erupted between 1.2 and 1.6 Ma. All Little Barrier lavas are strongly porphyritic and contain phenocrysts of plagioclase, orthopyroxene, and hornblende. Geochemically, they are subduction related and distinct from the older lavas of the Coromandel Volcanic Group, being Zr rich but Rb and Ba poor. Their Sr and Nd isotope ratios are similar to those of the Tonga-Kermadec arc volcanoes. Modelling of the dacite supports petrographic evidence that recharge and mixing were important in the magmatic system. Little Barrier and two dacite domes of similar age and composition near Whangarei form a northwest-trending lineament subparallel to the Alexandra Volcanics and the Vening Meinesz Fracture Zone.

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Section: Haowhenua Formationmentioning

confidence: 99%

Geology, petrology, and petrogenesis of Little Barrier Island, Hauraki Gulf, New Zealand

Lindsay

Worthington

Smith

et al. 1999

New Zealand Journal of Geology and Geophysics

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“…K was analysed by flame photometry using a 2000 ppm Cs buffer and has an analytical error within 2% at the 2o confidence level. Ar was analysed on a 15 cm radius sector-type mass spectrometer with a single collector system, using an isotopic dilution method and an Ar38 spike (Itaya et al 1991). The decay constants for 40 K and 40 Ca, and the 40 K content in potassium used in the age calculations are from Steiger & Jager (1977), and are 0.581 x 10" 10 /yr, 4.962 x 10 10 /yr, and 0.0001167, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…Analyses of K and Ar in South Auckland basalts, and calculations of ages and errors, were carried out at the Hiruzen Research Institute (Okayama, Japan) using the methods described by Nagao et al (1984) and Itaya et al (1991). Samples for K-Ar analysis were prepared using the procedure described by Briggs et al (1989).…”

Section: Methodsmentioning

confidence: 99%

K‐Ar ages, paleomagnetism, and geochemistry of the South Auckland volcanic field, North Island, New Zealand

Briggs

Okada

Itaya

et al. 1994

New Zealand Journal of Geology and Geophysics

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The South Auckland volcanic field is one of the Pliocene-Quaternary intraplate basaltic fields in northern North Island. It consists of at least 97 monogenetic volcanic centres covering an area of c. 300 km 2 , 38 km south of Auckland. Fifty-nine of the volcanic centres are characterised by mainly magmatic or effusive activity that constructed scoria cones and lava flows, while 38 are mainly phreatomagmatic or explosive that produced tuff rings and maars. Rock types consist of basanites, hawaiites, nepheline hawaiites, transitional basalts, and oZ-tholeiitic basalts, with relatively minor amounts of nephelinites, alkali basalts, Qtholeiitic basalts, and nepheline mugearites. Forty-three new K-Ar ages are presented, which range from 0.51 to 1.59 Ma, and show two peaks of activity at 0.6 and 1.3 Ma. Paleomagnetic determinations at 26 selected sites agree well with the paleomagnetic reversal time scale and support the K-Ar age data. Age data from each of the volcanic fields of Okete, Ngatutura, South Auckland, and Auckland, which constitute the Auckland intraplate basaltic province, show that they have developed within a time span of 0.3-1.1 Ma. After activity ceased in any particular field, a new field then developed 35-38 km to the north. These consistent time/ space patterns indicate the possibility of a mantle source migrating northwards at c. 5 cm/yr. There is no correlation of rock composition with time, which is consistent with observations in the Northland intraplate province, but is not consistent with the formerly invoked rising diapir model.

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“…Muscovites and biotites were separated from the studied samples and dated using K -Ar method following the procedure described in Itaya et al (1991) and Gouzu et al (2006). The analytical results are summarized in Table 1.…”

Section: K-ar Agesmentioning

confidence: 99%

K-Ar ages of biotite and muscovite from Pangong metamorphic complex, Shyok suture zone, India: Implications for the youngest post-collision metamorphic event in Ladakh Himalaya

Thanh

Itaya

Sajeev³

et al. 2009

Journal of Mineralogical and Petrological Sciences

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The garnet -kyanite -staurolite and garnet -biotite -staurolite gneisses were collected from a locality within Lukung area that belongs to the Pangong metamorphic complex in Shyok valley, Ladakh Himalaya. The kyanitefree samples have garnet and staurolite in equilibrium, where garnets show euhedral texture and have flat compositional profile. On the other hand, the kyanite -bearing sample shows equilibrium assemblage of garnetkyanite -staurolite along with muscovite and biotite. In this case, garnet has an inclusion rich core with a distinct grain boundary, which was later overgrown by inclusion free euhedral garnet. Garnet cores are rich in Mn and Ca, while the rims are poor in Mn and rich in Fe and Mg, suggesting two distinct generations of growth. However, the compositional profiles and textural signature of garnets suggests the same stage of P -T evolution for the formation of the inclusion free euhedral garnets in the kyanite -free gneisses and the inclusion free euhedral garnet rims in the kyanite -bearing gneiss. Muscovites from the four samples have consistent K -Ar ages, suggesting the cooling age (~ 10 Ma) of the gneisses. These ages make a constraint on the timing of the youngest post -collision metamorphic event that may be closely related to an activation of the Karakoram fault in Pangong metamorphic complex.

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Argon isotope analysis by a newly developed mass spectrometric system for K-Ar dating.

Cited by 244 publications

References 18 publications

Geology, petrology, and petrogenesis of Little Barrier Island, Hauraki Gulf, New Zealand

Geology, petrology, and petrogenesis of Little Barrier Island, Hauraki Gulf, New Zealand

K‐Ar ages, paleomagnetism, and geochemistry of the South Auckland volcanic field, North Island, New Zealand

K-Ar ages of biotite and muscovite from Pangong metamorphic complex, Shyok suture zone, India: Implications for the youngest post-collision metamorphic event in Ladakh Himalaya

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