Re-examination on K-Ar age of the Kumano Acidic Rocks in Kii Peninsula, Southwest Japan.

朝昭, 角井; 茂, 内海; 裕尚, 新正; 玄, 下田

doi:10.5575/geosoc.104.387

Cited by 39 publications

(24 citation statements)

References 9 publications

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“…At the beginning of studies on ages of the Outer Zone Granites, however, an age of each granite was estimated using data from one locality without investigation of its cooling history (Shibata and Nozawa, 1967). Recent researches (e.g., Murakami et al, 1989;Iwaya and Mimura, 1992;Dai et al, 1993;Hasebe et al, 1993;Tagami and Shimada, 1996;Sumii et al, 1998) re-estimate their emplacement ages carefully, still supporting the contemporaneity of the Outer Zone Granite intrusion.…”

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confidence: 99%

Fission track ages of the Omine Acidic Rocks, Kii Peninsula, Southwest Japan.

Hasebe

Suwargadi

Nishimura³

2000

Geochem. J.

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Fission track (FT) ages of the Omine Acidic Rocks, one of the Tertiary granitic rocks which occurs in the Outer Zone of the Median Tectonic Line, Southwest Japan, are determined in order to assess the timing of intrusion. Nine FT zircon (ZR) ages and one apatite (AP) age are obtained for igneous rocks, and four ZR ages for basement sandstone. Data for each pluton are concordant within a body representing the time of intrusion. The ZR ages from sandstone are concordant with the nearest pluton. The ages of plutons are classified into two groups statistically, suggesting that the Omine Acidic Rocks formed by two intrusive events. The Dorogawa, Tenguyama, Shiratani and Katago-Mukuro Dike are the older group with the weighted mean age of 16.8 ± 0.8 Ma, and the Kose pluton are the younger with an age of 14.2 ± 1.7 Ma. magma intrusion and tectonic framework at the time. Because of their possible complicated histories, the emplacement ages of granites should be estimated after investigation of their cooling histories by means of an age mapping and a combination of several dating techniques. At the beginning of studies on ages of the Outer Zone Granites, however, an age of each granite was estimated using data from one locality without investigation of its cooling history (Shibata and Nozawa, 1967).

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confidence: 99%

Fission track ages of the Omine Acidic Rocks, Kii Peninsula, Southwest Japan.

Hasebe

Suwargadi

Nishimura³

2000

Geochem. J.

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“…The biotite K–Ar ages of Konogi rhyolite, the granite porphyry and the cone sheet are 14.2 ± 0.2 Ma, 14.4 ± 0.1 Ma and 14.3 ± 0.2 Ma, respectively, which coincide with each other within the margin of error (Sumii et al . 1998).…”

Section: Geological Settingmentioning

confidence: 65%

“…The diamonds indicate the experimental errors of the radiometric ages. The radiometric ages of the Kumano Acidic Rocks are after Sumii et al . (1998) and that of the Muro Pyroclastic Flow Deposit is after Uto et al .…”

Section: Resultsmentioning

confidence: 99%

“…The ages of the main geological unit in the neighboring area have been estimated with rather good precision. For example, the biotite K–Ar ages were reported on the Kumano Acidic Rocks as 14.2 ± 0.2 Ma, 14.4 ± 0.1 Ma and 14.3 ± 0.2 Ma (Sumii et al . 1998), and that of the Muro Pyroclastic Flow Deposit was reported as 14.44 ± 0.16 Ma (Uto et al .…”

Section: Geological Settingmentioning

confidence: 99%

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K–Ar ages of the Ohmine Granitic Rocks, south‐west Japan

Sumii

Shinjoe

2003

Island Arc

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The Ohmine Granitic Rocks are a series of granitic rocks that are distributed in a chain stretching along the central axis of the Kii Peninsula. Their precise ages have not been determined, although precise ages have been reported for other geological units of the early to middle Miocene distributed over the peninsula. In this study, biotite K–Ar ages were obtained for the six major granitic plutons of the Ohmine Granitic Rocks: Dorogawa, Shirakura, Kose, Asahi, Tenguyama and Shiratani. Most are aged from 14.8 to 14.6 Ma. Although one pluton is older (15.4 ± 0.2 Ma) and two are younger (14.0 ± 0.2 Ma and 13.4 ± 0.1 Ma), these ages are excluded from the discussion of the mutual correlation among the plutons because some ambiguities exist in their ages. The age of the southernmost unit, the Katago–Mukuro Dykes, was not determined because of its intense alteration, but stratigraphic constraints suggest that it is younger than 16.1 Ma. The majority of the Ohmine Granitic Rocks concentrate within a narrow age window of approximately 14.8–14.6 Ma, although their geochemical/petrographical characteristics suggest that they were generated by multiple magma batches. The results of this study also reveal the simultaneous occurrence of the major activities of the Ohmine Granitic Rocks and the gigantic felsic igneous activities in the Kii Peninsula, such as the Kumano Acidic Rocks and the Muro Pyroclastic Flow Deposit.

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“…1). Radiometric dating shows that the magmatism took place in a short time‐span at 14 ± 1 Ma ( Shibata 1978; Sumii et al 1998 ). Most felsic magmas intruded into the Shimanto belt, a Cretaceous to Miocene subduction complex composed mainly of terrigenous shale and sandstone.…”

Section: Geologymentioning

confidence: 99%

Generation of rhyolite magmas by melting of subducting sediments in Shodo‐Shima island, Southwest Japan, and its bearing on the origin of high‐Mg andesites

Shimoda¹,

Tatsumi²

1999

Island Arc

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Geochemical characteristics of rhyolites from the Miocene Setouchi volcanic belt in the Southwest Japan arc were examined. The following observations may be best explained by the derivation of rhyolite magmas by melting of subducting sediments as follows. (i) Sr‐Nd‐Pb isotope compositions of Setouchi rhyolites are close to those of the local trench‐fill sediments; (ii) major element compositions of rhyolites are identical to those of experimentally produced sediment melts; and (iii) concentrations of incompatible elements in rhyolites are consistent with partial melting of the local trench‐fill sediments in the presence of residual garnet. Furthermore, trace element and isotope signatures of Setouchi high‐Mg andesites can be also rationalized by interaction of such rhyolitic sediment melts with overlying mantle peridotites.

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Re-examination on K-Ar age of the Kumano Acidic Rocks in Kii Peninsula, Southwest Japan.

Cited by 39 publications

References 9 publications

Fission track ages of the Omine Acidic Rocks, Kii Peninsula, Southwest Japan.

Fission track ages of the Omine Acidic Rocks, Kii Peninsula, Southwest Japan.

K–Ar ages of the Ohmine Granitic Rocks, south‐west Japan

Generation of rhyolite magmas by melting of subducting sediments in Shodo‐Shima island, Southwest Japan, and its bearing on the origin of high‐Mg andesites

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