Melting features along the western Ryukyu slab edge (northeast Taiwan): Tomographic evidence - art. no. B12402

Type Article
Date 2004-12
Language English
Author(s) Lin Jing-Yi, Hsu Sk, Sibuet Jean-Claude
Affiliation(s) IFREMER, Ctr Brest, F-29280 Plouzane, France.
Natl Cent Univ, Inst Geophys, Chungli 32054, Taiwan.
Source Journal Of Geophysical Research Solid Earth (0148-0227) (Amer Geophysical Union), 2004-12 , Vol. 109 , N. B12 , P. -
DOI 10.1029/2004JB003260
WOS© Times Cited 92
Keyword(s) Ryukyu slab, Okinawa Trough, seismic tomography, melting features
Abstract [1] Behind the sedimentary Ryukyu arc lies the Okinawa Trough, whose termination is located at the tip of the Ilan plain ( northern Taiwan), just above the Ryukyu slab edge. The present-day active volcanic front is located 80 - 100 km above the Ryukyu slab and extends from Japan to Kueishantao Island, an islet situated 10 km offshore the Ilan plain. Between December 1990 and May 1999, 3370 earthquakes recorded in northern Taiwan by 65 seismic land stations were used to determine the three-dimensional V-p and V-s velocity structures and V-p/V-s ratios. A low V-s but high V-p/V-s sausage-like body, similar to 30 km in diameter, lies within the Eurasian mantle wedge, on top of the western Ryukyu slab extremity, at depths ranging between 20 and 100 km. We suggest that the H2O-rich component formed by dehydration processes from subducting sediments, oceanic crust, and serpentinized mantle above the Ryukyu slab and along the vertical portion of the slab edge might explain the presence of the sausage-like body. A low V-s but high V-p/V-s channel rises obliquely from the sausage-like body at a depth of 40 km in direction of the andesitic Kueishantao Island. We propose that the H2O-rich component and/or melt rise up from the sausage-like body and interfere with the Okinawa Trough back arc basin magmas formed in the upper mantle/lower crust. Then magmas propagate upward within the upper brittle crust through veins and/or narrow conduits.
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