HR: 0800h
AN: V21D-0642    [Abstracts]
TI: Evolution of magma plumbing systems in the late Cenozoic NE Honshu arc, Japan
AU: * Yoshida, T
EM: tyoshida@mail.tains.tohoku.ac.jp
AF: Institute of Mineralogy, Petrology and Economic Geology, Graduate School of Science, Tohoku University, 6-3 Aramaki-aza-Aoba, Aoba-ku, Sendai, 980-8578 Japan
AU: Acocella, V
EM: acocella@uniroma3.it
AF: Dipartimento Scienze Geologiche, Universita Roma Tre, Largo S.L., Murialdo, Roma, 100146 Italy
AU: Nakajima, J
EM: nakajima@aob.geophys.tohoku.ac.jp
AF: Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, 6-3 Aramaki-aza-Aoba, Aoba-ku, Sendai, 980-8578 Japan
AU: Hasegawa, A
EM: hasegawa@aob.geophys.tohoku.ac.jp
AF: Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, 6-3 Aramaki-aza-Aoba, Aoba-ku, Sendai, 980-8578 Japan
AU: Sato, H
EM: satow@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032 Japan
AU: Nagahashi, Y
EM: nagahashi@sss.fukushima-u.ac.jp
AF: Faculty of Education, Fukushima University, 1 Kanayagawa, Fukushima, 960-1296 Japan
AU: Kimura, J
EM: jkimura@riko.shimane-u.ac.jp
AF: Department of Geoscience, Shimane University, 1060 Nishi-Kawazu-cho, Matsue, 690-8504 Japan
AU: Tanaka, A
EM: akiko-tanaka@aist.go.jp
AF: Geological Survey of Japan, AIST, Tsukuba Central 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AB: NE Honshu, Japan is an island arc associated with the back-arc Japan Sea basin. Recent advances in seismic tomography enable visualization of the crust-mantle structures beneath the NE Honshu arc. Combined with geology and petrology, the seismic images have become valuable tools for revealing the mantle to crustal structures of the arc. The structure of the present mantle to crust inferred from geological and petrological data correlated well with the 3D seismic structures. Intra-crustal thermal structures would have been affected by intensive magma intrusions to form large magma storages beneath the late Miocene to Pliocene calderas in the NE Honshu arc. The remnants of these thermal disturbances are still detectable by seismology. Geological and petrological studies of the late Cenozoic volcanic rocks from the NE Honshu arc have revealed secular variations in the magmatism. These variations are closely related with tectonic evolution of the arc. The island-arc stage in the NE Honshu arc can be subdivided into four substages. These are submarine volcanism (13.5-8Ma), late Miocene caldera-forming (8-5.3Ma), Pliocene caldera-forming (5.3-1.7Ma), and Quaternary stratovolcano-forming (1.7-0Ma) substages. Changes in mode of eruption reflect the intra-crustal stress regime controlled mainly by the plate motion. The reflection experiments (Sato et al., 2002) of the distribution area of the late Cenozoic calderas were confirm the existence of hot, solidified remnant of laccolithic magma reservoir with fluid-saturated top beneath the late Miocene caldera at depth of 3-5 km. The seismic tomography also show that the existence of hot, solidified magma reservoirs beneath the each late Miocene and Pliocene calderas at depths of 3-7 km and 10-15 km, respectively. The site of caldera-forming reservoirs migrated to the back-arc side and depths of the magma reservoirs increased with time from the late Miocene to the Quaternary. And, the magma plumbing systems changed from laccolith associated with piston-cylinder type caldera to vertically elongated stock associated with funnel type caldera. Many Quaternary stratovolcanoes located on the walls of these preexisting calderas.
DE: 7270 Tomography (6982, 8180)
DE: 8035 Pluton emplacement
DE: 8185 Volcanic arcs
DE: 8413 Subduction zone processes (1031, 3060, 3613, 8170)
DE: 8440 Calderas
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005