scholarly journals Paleomagnetic Studies on Miocene Sequences of Hokutan and Tottori Groups in Southwest Japan: Implications for Middle Miocene Rotational Movement of Southwest Japan Block Associated with the Japan Sea Opening

10.5772/67960 ◽  
2017 ◽  
Author(s):  
Naoto Ishikawa ◽  
Takashi Suzuki ◽  
Shiro Ishida
Keyword(s):  
Middle Miocene ◽  
Japan Sea ◽  
Southwest Japan ◽  
Rotational Movement ◽  
The Japan Sea

U–Pb ages of Miocene near-trench granitic rocks of the Southwest Japan arc: implications for magmatism related to hot subduction

2019 ◽  
Vol 158 (1) ◽  
pp. 47-71 ◽  
Author(s):  
Hironao Shinjoe ◽  
Yuji Orihashi ◽  
Ryo Anma
Keyword(s):  
Middle Miocene ◽  
Japan Sea ◽  
Wide Distribution ◽  
Granitic Rocks ◽  
Philippine Sea Plate ◽  
Kii Peninsula ◽  
The Japan Sea ◽  
Igneous Activity ◽  
Mariana Arc ◽  
Back Arc

AbstractWe present a new dataset of zircon U–Pb ages that document igneous activity in the SW Japan arc during middle Miocene time and discuss its relationship with the opening of the Japan Sea, Philippine Sea plate migration, and subduction of the young hot lithosphere of the Shikoku Basin. Precursory magmatism, characterized by dike and stock intrusions, started c. 15.6 Ma in both Kyushu and the Kii Peninsula. Most plutonism occurred between 15.5 and 13.5 Ma in an area 600 km long and 150 km wide. No along-arc trend was recognized in the U–Pb ages of igneous activity near the trench. Our data indicate that all near-trench middle Miocene igneous activity occurred immediately after the opening of the Japan Sea ceased, i.e. after 16 Ma, implying that melt extraction and the emplacement of granites in the near-trench region had some influence on the back-arc opening. Our data also imply that the trench–trench–trench-type triple junction between the Japan arc and the Izu–Bonin–Mariana arc must have reached the east side of the Kii Peninsula by 15.6 Ma. The wide distribution of contemporaneous magmatic activity along the arc requires a trench-parallel heat source, such as the subduction of a trench-parallel ridge or a young and highly segmented ridge–fracture zone system in addition to the hot wedge mantle condition related to the opening of Japan Sea.

Neogene deformation of the back-arc shelf of Southwest Japan and its impact on the palaeoenvironments of the Japan Sea

1997 ◽  
Vol 281 (1-2) ◽  
pp. 71-82 ◽  
Author(s):  
Yasuto Itoh ◽  
Takeshi Nakajima ◽  
Atsushi Takemura
Keyword(s):  
Japan Sea ◽  
Southwest Japan ◽  
The Japan Sea ◽  
Back Arc

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

2004 ◽  
Vol 141 (1) ◽  
pp. 1-13 ◽  
Author(s):  
T. IMAOKA ◽  
T. ITAYA
Keyword(s):  
Basaltic Andesite ◽  
Large Scale ◽  
Middle Miocene ◽  
Tectonic Setting ◽  
Japan Sea ◽  
Contact Metamorphism ◽  
Southwest Japan ◽  
Tectonic Event ◽  
Plutonic Complex ◽  
In The Beginning

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 40Ar/36Ar 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.

When was the Japan Sea Opened?: Paleomagnetic Evidence from Southwest Japan

1985 ◽  
pp. 551-566 ◽  
Author(s):  
Yo-ichiro Otofuji ◽  
Akira Hayashida ◽  
Masayuki Torii
Keyword(s):  
Japan Sea ◽  
Southwest Japan ◽  
The Japan Sea

Radiolarian Biostratigraphy from Middle Miocene to Late Pleistocene in the Japan Sea

2017 ◽  
Vol 21 (4) ◽  
pp. 397-421 ◽  
Author(s):  
Shin-Ichi Kamikuri ◽  
Takuya Itaki ◽  
Isao Motoyama ◽  
Kenji M. Matsuzaki
Keyword(s):  
Late Pleistocene ◽  
Middle Miocene ◽  
Japan Sea ◽  
The Japan Sea ◽  
Radiolarian Biostratigraphy
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