Initiation of arc magmatism in an embryonic continental rifting zone of the southernmost part of Okinawa Trough |
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| Authors: | S-L Chung S-L Wang R Shinjo C-S Lee & C-H Chen |
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| Institution: | Department of Geosciences, National Taiwan University, 245 Choushan Road, Taipei 106, Taiwan;Department of Geosciences, National Taiwan University, 245 Choushan Road, Taipei 106, Taiwan;Department of Physics and Earth Sciences, University of the Ryukyus, Okinawa, Japan;Institute of Applied Geophysics, National Taiwan Ocean University, Keelung, Taiwan;Department of Geosciences, National Taiwan University, 245 Choushan Road, Taipei 106, Taiwan |
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| Abstract: | The Okinawa Trough is a young, intracontinental backarc basin that has formed behind the Ryukyu arc–trench system since late Miocene time. In the Southernmost Part of the Okinawa Trough (SPOT), a cluster of active submarine volcanoes delineates a volcanic belt, which is located only ∼100 km above the Wadati–Benioff zone. We report herein new major and trace element data for the SPOT volcanic rocks. These rocks show a compositional range from medium-K andesite to rhyolite. Their geochemical characteristics are similar to those of pre-backarc rifting volcanic rocks from the central Ryukyu arc, and different from those of backarc basin lavas from the Middle Okinawa Trough and the post-backarc rifting Ryukyu arc volcanics. Therefore, despite being topographically contiguous with the rest of the Trough, the SPOT that developed in the Quaternary is not a simple backarc basin but instead an embryonic rift zone in which early arc volcanism occurs as a result of the Ryukyu subduction. |
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