HR: 1340h
AN: V33C-1526    [Abstracts]
TI: Magnetotelluric imaging of the Miocene Kumano-Omine volcano-plutonic complex in the Kii Peninsula, southwest Japan
AU: * Umeda, K
EM: umeda.koji@jaea.go.jp
AB: The Kumano Acidic Rocks and the Omine Granitic Rocks, which are located in the Kii Peninsula, southwest Japan, is representative of the large igneous complexes in the Middle Miocene. They are adjacent each other within several kilometers and generally extend along the Omine Mountains in an N-S direction. A wide-band magnetotelluric survey was carried out with a 50 km long MT profile running across the Omine Mountains in order to image the deep crustal structure of the Kumano Acidic Rocks and the Omine Granitic Rocks. A body with high resistivity (~1000 ohm) is clearly visible in the subsurface shallower than 20 km, which corresponds to the distribution of the Omine Granitic Rocks and the western part of the Kumano Acidic Rocks. The resistive body extends to about 20 km depth and widens with increasing depth. The model suggests that these two igneous complexes are connected in the subsurface rather than discrete resistive body corresponds to either igneous complex. Radiometric ages, geochemical compositions and other geological data also support that the resistive body represents the fossil of large silicic magma system in relation to the Kumano-Omine volcano-plutonic complex. It has been established that relative uplift took place in the central part of Kii Peninsula after the Miocene. Therefore, the top part of the Omine Mountains on which the Omine Granitic Rocks are distributed has likely undergone more exhumation than the coastal area in which the Kumano Acidic Rocks are located. As a result, the Kumano Acidic Rocks and the Omine Granitic Rocks may correspond to the shallower and the deeper parts respectively, of the Kumano-Omine volcano-plutonic complex.
DE: 5109 Magnetic and electrical properties (0925)
DE: 8035 Pluton emplacement
DE: 8439 Physics and chemistry of magma bodies
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting