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Cretaceous to Miocene NW Pacific Plate kinematic constraints: Paleomagnetism and Ar-Ar geochronology in the Mineoka Ophiolite Melange (Japan)
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  • Ariuntsetseg Ganbat,
  • Daniel Pastor-Galán,
  • Naoto Hirano,
  • Norihiro Nakamura,
  • Hirochika Sumino,
  • Tatsuki Tsujimori,
  • Yuji Yamaguchi
Ariuntsetseg Ganbat
Tohoku University
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Daniel Pastor-Galán
Center for Northeast Asian Studies 41 Kawauchi Aoba-ku, Sendai Miyagi, 980-8576, Japan

Corresponding Author:[email protected]

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Naoto Hirano
Tohoku University
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Norihiro Nakamura
Institute for Excellence in Higher Education
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Hirochika Sumino
University of Tokyo
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Tatsuki Tsujimori
Tohoku University
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Yuji Yamaguchi
Nippon Koei Ltd
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The Mineoka Ophiolite Melange is located at the intersection of the Pacific, Philippine Sea, Eurasia and North American plates. The origin of the Mineoka ophiolite is disputed and it has been ascribed to a fully subducted plate or part of the Pacific and Philippine Sea plates. In this paper, we present a kinematic reconstruction of the Mineoka Ophiolite Melange and its relation with the Pacific Plate, based on new paleomagnetic data and Ar-Ar geochronology. In addition to standard analyses for paleolatitudes, we performed a Net Tectonic Rotation analysis on sheeted dykes to infer the paleospreading direction that formed the ophiolite. The analysis show that 85–80 Ma MORB pillow lavas erupted at a paleolatitude of N ~16˚, whereas ca. 50 Ma pillow lavas formed at N ~34˚. Net Tectonic Rotation analysis suggests that the spreading direction was NE 60˚. Ar-Ar ages yielded 53–49 Ma for MOR lavas and 41–35 Ma for island arc volcanism. The formation of this ophiolite occurred in the back-arc spreading of the Nemuro-Olyutorsky arcs of the NW Pacific. It infers that the final consumption of Izanagi below Japan instigated a subduction jump and flipped its polarity. Subduction initiated parallel to the ridge, and a piece of the original back-arc crust got trapped near the Japan trench during the northwards motion of the Philippine Sea Plate. The contrasting motion between the Pacific and Philippine Sea plates generated a highly unstable setting followed by a subduction zone that left a small-sized and short-lived plate, surrounded by subduction zones.
May 2021Published in Journal of Geophysical Research: Solid Earth volume 126 issue 5. 10.1029/2020JB021492