K-Ar ages of neogene volcanic rocks from Northeast Japan. 1. the Mitaki and the Takadate formations from Sendai district, Miyagi Prefecture.

浩三, 宇都; 賢, 柴田; 茂, 内海

doi:10.5575/geosoc.95.865

Cited by 17 publications

(15 citation statements)

References 8 publications

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“…Six volcanoes and volcanic fields along the volcanic front of the Miocene NE Japan arc were selected for this study (Figure 1). Previous K‐Ar age data dated magmatic activity at Choshi at 21 Ma [ Seno et al , 1986], the Tomari volcanism at 14 Ma [ Watanabe et al , 1993] and the Mitaki volcanism at 8 Ma [ Uto et al , 1989]. The binary volcanic activities have been identified for Ryozen formations (22 and 15 Ma [ Tsunakawa et al , 1983; Ohki et al , 1993a]) and the Takadate formations (22 and 15 Ma [ Uto et al , 1989]).…”

Section: Geological Background and Samplesmentioning

confidence: 99%

Contribution of slab melting and slab dehydration to magmatism in the NE Japan arc for the last 25 Myr: Constraints from geochemistry

Hanyu

Tatsumi

Nakai

et al. 2006

Geochem Geophys Geosyst

196

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[1] Hf isotope compositions, coupled with Pb-Sr-Nd isotopes and trace element compositions, for the Miocene to the Quaternary volcanic rocks from the NE Japan arc have documented the geochemical evolution in the magma source compositions in association with back-arc opening (23-14 Ma). Clear temporal variation in Hf isotope ratios is demonstrated, from the lowest e Hf (+9) in the early Miocene to the highest e Hf (+14) in the late Miocene and the Quaternary, whereas there are little changes in Sr and Nd isotope composition. Hf isotope ratios are clearly correlated with some trace elemental ratios. The observed temporal variation is attributed to a change in metasomatic agents derived from the subducted slab, which could have been caused by cooling of the mantle wedge during the syn and post stages of the back-arc opening. In the early stage of the back-arc opening, when injection of hot asthenospheric mantle induced high-temperature conditions in the mantle wedge, slab melting contributed to low e Hf coupled with low e Nd , relatively low La/Nb, and high Th/Yb in volcanic rocks. On the other hand, the later stage volcanism, characterized by high e Hf , decoupling of e Hf and e Nd , high and variable La/Nb and Ba/La, is best explained by addition of fluids from subducted sediments and oceanic crust to the mantle wedge.

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Section: Geological Background and Samplesmentioning

confidence: 99%

Contribution of slab melting and slab dehydration to magmatism in the NE Japan arc for the last 25 Myr: Constraints from geochemistry

Hanyu

Tatsumi

Nakai

et al. 2006

Geochem Geophys Geosyst

196

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“…The Takadate Formation, which is distributed in an area to the south of Sendai, composed of basalt‐dacite lava flows, lava domes, and minor pyroclastics belonging to high‐aluminum basaltic series (Abe & Aoki 1969; Oide & Fujita 1975; Kitamura et al 1986). The whole rock K‐Ar data reported from this area split into younger (13, 15 Ma) and older (21, 22 Ma) age groups (Konda & Ueda 1980; Uto et al 1989). The difference of 6 Myr between these two groups has been attributed to either dormancy in the volcanic activities or the shift of volcanic front in NE Japan (Tsunakawa et al 1983; Ohki et al 1993b).…”

Section: Geological Setting and Samplingmentioning

confidence: 99%

New age constraints on counter-clockwise rotation of NE Japan

Baba¹,

Matsuda

Itaya

et al. 2007

Geophysical Journal International

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S U M M A R YThe Miocene basaltic-andesitic lavas and Cretaceous granites were sampled in the Abukuma Terrane of northeast Honshu for geochronological and palaeomagnetic investigations to determine precise timing of counter-clockwise rotation of NE Japan. Characteristic component with unblocking temperature of 560-590 • C is isolated from 26 sites of the Takadate and Ryozen Formations and 12 sites of the Cretaceous granites. Concordant northwesterly palaeomagnetic directions (D = 265 • -331 • ) are observed in the Cretaceous granites of the Abukuma Terrane. The Cretaceous mean-palaeomagnetic direction from this terrane (D = 313.5 • , I = 54.6 • , α 95 = 6.3 • and N = 20) is almost identical to Oligo-Miocene (33-20 Ma) palaeomagnetic direction reported from the Japan Sea side of NE Japan as well as to the Cretaceous palaeomagnetic direction reported from the Kitakami Terrane. This type of behaviour clearly suggests that the Abukuma Terrane underwent a coherent counter-clockwise rotation as a part of NE Japan after 20 Ma. Conventional potassium (K)-Argon (Ar) dating method performed on the plagioclase grains revealed distinctive ages of 14.44 ± 0.88 and 16.52 ± 0.82 Ma for the Takadate Formation (11 sites) and the Ryozen Formation (eight sites), respectively. This type of behaviour indicates that two independent episodes of volcanic activities were probably responsible for the production of igneous rocks in the Takadate and Ryozen areas. Northerly declination is obtained from the Takadate Formation (D = 355.3 • , I = 39.4 • , α 95 = 11.6 • ), while slightly westerly deflected declination appears in the Ryozen Formation (D = 333.5 • , I = 58.0 • and α 95 = 9.6 • ). The here presented results, therefore, suggest that the province of NE Japan was still experiencing a counter-clockwise rotation at 16.5 Ma, however by 14.4 Ma the rotational motion has completely ceased. Compared with the available palaeomagnetic and geochronological data from SW Japan, rotational motion in both provinces of NE and SE Japan has already been ceased by 14 Ma. Thus any additional evidence regarding the complete cessation of rotational motions in NE Japan will provide a key to understand the timing of opening in the Japan Sea.

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“…As a result, the composition of magma sources for the volcanic rocks and the mechanism of magma generation around the NE Japan arc should have changed (Kurasawa and Konda 1986;Nohda et al 1988;Shuto et al 1992bShuto et al , 1993. Despite the dynamic changes in tectonic and volcanic environments around the NE Japan arc, several workers have considered that the volcanic front from the Early to Mid-Miocene was similar in situation to the Quater-Accepted for publication 2 May 1993. nary volcanic front (QVF) (Tsunakawa et al 1983;Uto et al 1989). …”

Section: Introductionmentioning

confidence: 99%

“…1986; Agency of Natural Resources and Energy 1981, 1982b, Suto and lshii 1982Suzuki 1982, Konda and Ueda 1980, Kimura 1983, Usuta and Okamoto 1986, Tsunakawa et a/. 1983, Uto et a/. 1989, Fukudome et a/.…”

Section: Introductionmentioning

confidence: 99%

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Shifting of the volcanic fronts during Early to Late Miocene in the Northeast Japan arc

et al. 1993

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Recent advanced chronological studies for the Tertiary volcanic rocks from the Northeast (NE) Japan arc revealed three volcanic fronts which differed in temporal and spatial distribution. These fronts were (i) the Matsumae-Shizukuishi-Shiogama line of 22-25 Ma which is obliquely across the Quaternary volcanic front (QVF) ; (ii) the Tomari-Shiogama line of 13-16 Ma which exists 30-50 km east of the QVF and (iii) a line of 0-8 Ma which is the same as the QVF. The first shifting of the 22-25 Ma line to the 13-16 Ma one was due to the counterclockwise rotation of the NE Japan arc during 20-12 Ma as proposed by Otofuji et al. (1985), and the second shifting of the 13-16 Ma line to the 0-8 Ma line could have contributed to a decrease in the dip of the slab of the Pacific plate which subducted beneath the NE Japan arc during 13-8 Ma.

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K-Ar ages of neogene volcanic rocks from Northeast Japan. 1. the Mitaki and the Takadate formations from Sendai district, Miyagi Prefecture.

Cited by 17 publications

References 8 publications

Contribution of slab melting and slab dehydration to magmatism in the NE Japan arc for the last 25 Myr: Constraints from geochemistry

Contribution of slab melting and slab dehydration to magmatism in the NE Japan arc for the last 25 Myr: Constraints from geochemistry

New age constraints on counter-clockwise rotation of NE Japan

Shifting of the volcanic fronts during Early to Late Miocene in the Northeast Japan arc

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