HR: 17:30h
AN: T44A-07    [Abstracts]
TI: Relationship Between the West Philippine Basin and the Early Izu-Bonin-Mariana Arc: Arc Initiation and Ancestry
AU: * Hickey-Vargas, R
EM: hickey@fiu.edu
AF: Department of Earth Sciences, Florida International University, Miami, FL 33199 United States
AU: Savov, I P
EM: savovi@si.edu
AF: Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560 United States
AU: Bizimis, M
EM: bizimis@magnet.fsu.edu
AF: National High Magnetic Field Laboratory and Department of Geosciences, Florida State University, Tallahassee, FL 32310 United States
AB: The early Izu-Bonin-Mariana (IBM) arc formed during the Eocene along a margin of the West Philippine Basin (WPB). At that time, the WPB had at least one active spreading center, the Central Basin Ridge (CBR) and it was rimmed by fragments of older, Early Cretaceous to Paleocene island arc and ocean floor lithosphere. Published models of IBM arc initiation suggest that subsidence and ultimately subduction of old, dense oceanic lithosphere beneath the young oceanic lithosphere near the CBR, which was either an active mid-ocean ridge or a back-arc basin spreading center, triggered melting to form boninite and primitive arc tholeiite. Published ages of rocks from the CBR show that magmatism continued until at least 28 Ma, which implies that CBR and early IBM arc magmatism overlapped for almost 20 Ma. Geochemical data for rocks from the WPB and from surrounding older arcs and basins, including the Amami Plateau, Daito Ridge and Huatung basin, indicate that WPB lithosphere was diverse in composition. This diversity probably influenced the along-strike character of the IBM arc as it evolved from its initiation at 48 Ma to the first episode of arc rifting and opening of the Shikoku and Parece Vela back-arc basins. In contrast, there is little geochemical evidence that the newly subducting plate influenced the composition of magma generated concurrently in the WPB.
DE: 1031 Subduction zone processes (3060, 3613, 8170, 8413)
DE: 1040 Radiogenic isotope geochemistry
DE: 1065 Major and trace element geochemistry
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
DE: 8185 Volcanic arcs
SC: Tectonophysics [T]
MN: Fall Meeting 2005