Results 221 to 230 of about 3,313 (254)
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Tectonophysics, 1994
Abstract Three distinctive geologic events occurred synchronously during the last 6 m.y. on Kyushu Island, lying at the junction of the Southwest Japan Arc and the Ryukyu Arc. These events included: (1) dextral-fault displacement along a 100 km section of the Median Tectonic Line; (2) formation of a rectangular volcano-tectonic depression 70 km long ...
Hiroki Kamata, Kazuto Kodama
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Abstract Three distinctive geologic events occurred synchronously during the last 6 m.y. on Kyushu Island, lying at the junction of the Southwest Japan Arc and the Ryukyu Arc. These events included: (1) dextral-fault displacement along a 100 km section of the Median Tectonic Line; (2) formation of a rectangular volcano-tectonic depression 70 km long ...
Hiroki Kamata, Kazuto Kodama
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Three-dimensional P- and S-wave velocity structures beneath the Ryukyu arc
Tectonophysics, 2003The three-dimensional (3-D) P- and S-wave velocity structures beneath the Ryukyu arc are determined by seismic wave travel time tomography, using recordings on temporary stations in the sea area as well as those on routine stations. For the inversion, we explicitly define the upper boundary of the Philippine Sea slab.
Masaki Nakamura +4 more
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Detailed volcanic morphology of Daisan-Miyako Knoll in the southern Ryukyu Arc
Marine Geology, 2018Abstract High-resolution bathymetric mapping using an autonomous underwater vehicle and a survey vessel was conducted at Daisan–Miyako Knoll in the southern Ryukyu Arc. This paper presents for the first time the detailed volcanic morphology of a submarine edifice that previously was poorly explored, and discusses its formation process and relation to
Hiroki Minami, Yasuhiko Ohara
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Quaternary volcanic front at the junction of the South-west Japan Arc and the Ryukyu Arc
Journal of Asian Earth Sciences, 1998Abstract The Hohi volcanic zone, a 70 by 40 km volcanic graben on Kyushu Island at the junction of the South-west Japan Arc and the Ryukyu Arc, has been formed since 6 Ma to the present. Quaternary volcanism, producing centers along a NE–SW trending line, the volcanic front, started at about 1.5 Ma.
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Earth and Planetary Science Letters, 2006
New Sr, Nd, and Pb isotopic data for Cenozoic basalts from northwest Kyushu, Japan and the Okinawa Trough, suggest that mantle sources feeding the Ryukyu ‘back-arc’ side volcanoes, represent a mixture of Pacific N-MORB mantle with EM2-rich components, with little or no EM1.
Nguyen Hoang, Kozo Uto
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New Sr, Nd, and Pb isotopic data for Cenozoic basalts from northwest Kyushu, Japan and the Okinawa Trough, suggest that mantle sources feeding the Ryukyu ‘back-arc’ side volcanoes, represent a mixture of Pacific N-MORB mantle with EM2-rich components, with little or no EM1.
Nguyen Hoang, Kozo Uto
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Contributions to Mineralogy and Petrology, 2000
The major and trace element and Pb–Sr–Nd isotopic compositions of Quaternary mafic lavas from the northern Ryukyu arc provide insights into the nature of the mantle wedge and its tectonic evolution. Beneath the volcanic front in the northern part of the arc, the subducted slab of the Philippine Sea Plate bends sharply and steepens at a depth of ∼80 km.
Ryuichi Shinjo +2 more
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The major and trace element and Pb–Sr–Nd isotopic compositions of Quaternary mafic lavas from the northern Ryukyu arc provide insights into the nature of the mantle wedge and its tectonic evolution. Beneath the volcanic front in the northern part of the arc, the subducted slab of the Philippine Sea Plate bends sharply and steepens at a depth of ∼80 km.
Ryuichi Shinjo +2 more
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Exhumation process of the Nago subduction-related metamorphic rocks, Okinawa, Ryukyu island arc
Tectonophysics, 2004Abstract The Kunigami zone in Okinawa is an extension of the Shimanto zone, Japan. The rocks make up the main part of the Nago metamorphic rocks, and such metamorphic rocks are exceptional in the Shimanto zone. The Anne complex, in the older Motobu zone, is also metamorphosed.
Mark Schoonover, Soichi Osozawa
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Miocene sandstone of ‘continental’ origin on Iriomote Island, southwest Ryukyu Arc, Eastern Asia
Journal of Asian Earth Sciences, 2004Abstract We evaluated the major mineral composition of 100 sandstone samples from the Iriomote Formation of the Yaeyama Group located at the southwestern end of the Ryukyu Islands, eastern Asia. These sandstones are feldspathic arenites. Paleocurrents inferred from these sandstones are generally from north to south.
Yu Saitoh, Fujio Masuda
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Opening mode of the Okinawa Trough: paleomagnetic evidence from the South Ryukyu Arc
Tectonophysics, 1990More than 250 samples of volcanics and sedimentary rocks were collected from the South Ryukyu Arc for paleomagnetic study and K-Ar dating. Stable primary components of magnetization were isolated from 18 sites after thermal demagnetization. The mean paleomagnetic direction for 15 Eocene volcanic sites (D = 30.1°, I = 40.3°, α95 = 10.3°) indicates a ...
M. Miki, T. Matsuda, Y. Otofuji
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Oblique Diapirism of the Yakushima Granite in the Ryukyu Arc, Japan
1997Field observations and structural analyses of the orientations of ductile flow fabrics and brittle fractures are used to infer diapiric rise of the Yakushima pluton into epizonal Paleogene sediments of an accretionary prism in Miocene times. Inside the pluton, preferred orientations of orthoclase megacrysts define a weak primary flow fabric.
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