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Sueoka, Shigeru; Kobayashi, Yumi*; Fukuda, Shoma; Kohn, B. P.*; Yokoyama, Tatsunori; Sano, Naomi*; Hasebe, Noriko*; Tamura, Akihiro*; Morishita, Tomoaki*; Tagami, Takahiro*
Tectonophysics, 828, p.229231_1 - 229231_17, 2022/04
Times Cited Count：1 Percentile：22.72(Geochemistry & Geophysics)The South Fossa Magna zone, central Japan, has been an active collision zone between the Honshu Arc and the Izu-Bonin Arc since the middle Miocene and provides an excellent setting for reconstructing the earliest stages of continent formation. Multi-system geo-thermochronometry was applied to different domains of the South Fossa Magna zone, together with some previously published data, to reveal mountain formation processes, i.e., vertical crustal movements. Nine granitic samples yielded zircon U-Pb ages of 10.2-5.8 Ma (
= 2), apatite (U-Th)/He (AHe) ages of 42.8-2.6 Ma ( = 7), and apatite fission-track (AFT) ages of 44.1-3.0 Ma ( = 9). Thermal history inversion modeling based on the AHe and AFT data suggested rapid cooling events confined within the study region at 
6-2 Ma. The Kanto Mountains may have undergone a domal uplift in association with their collision with the Tanzawa Block at 5 Ma. However, this uplift may have slowed down following the migration of the plate boundary and late Pliocene termination of the Tanzawa collision. The Minobu Mountains and possibly adjacent mountains may have been uplifted by the motional change of the Philippine Sea plate at 3 Ma. Therefore, the mountain formation in the South Fossa Magna zone was mainly controlled by collisions of the Tanzawa and Izu Blocks and motional change of the Philippine Sea plate. Earlier collisions of the Kushigatayama Block at 13 Ma and Misaka Block at 10 Ma appeared to have had little effect on mountain formation. Together with a 90 deg. clockwise rotation of the Kanto Mountains at 12-6 Ma, these observations suggest that horizontal deformation predominated during the earlier stage of arc-arc collision, and vertical movements due to buoyancy resulting from crustal shortening and thickening developed at a later stage.
Munakata, Masahiro; Tezuka, Hiroko*; Yokoyama, Naomi*; Matsuura, Yasutaka*
no journal, ,
In transport of radiological materials, Exposure scenario and assessment model based on a survey of transportation in Japan, was developed. Using the developed model, regulatory limits on non-fixed surface contamination for the transport was discussed.
Torii, Tatsuo; Kido, Hiroko*; Yokoyama, Naomi*; Kurosawa, Naohiro*; Akita, Manabu*; Nakamura, Yoshitaka*; Morimoto, Takeshi*; Ushio, Tomoo*; Kawasaki, Zenichiro*
no journal, ,
To evaluate the influence to which radon and its decay products cause the thunderstorm activity, a large area diffusion model of radon is constructed for an Australian northern part that is one of the most frequent region of the thunderstorm in the world. The advection and diffusion analysis of radon in the atmosphere was carried out, and it compared it with the measured result of the radon concentration in the region from the dry season to the rainy season.
Sueoka, Shigeru; Kobayashi, Yumi*; Fukuda, Shoma; Kohn, B. P.*; Yokoyama, Tatsunori; Sano, Naomi*; Hasebe, Noriko*; Tamura, Akihiro*; Morishita, Tomoaki*; Tagami, Takahiro*
no journal, ,
Multi-system thermochronometries were applied to the Izu collision zone, an active arc-arc collision zone in the central Japan, in order to reveal the mountain formation process. Nine granitic samples yielded zircon U-Pb ages of 10.2-5.8 Ma (n = 2), apatite (U-Th)/He ages of 42.8-2.6 Ma (n = 7), and apatite fission-track (AFT) ages of 44.1-3.0 Ma (n = 9). Thermal inversion analyses based on the AFT data suggest rapid cooling events at ca 5 Ma and 1 Ma in the collision zone and no such thermal/tectonic effect out of the zone. The Kanto Mountains are thought to be uplifted domally associated with the collision of the Tanzawa Block at ca 5 Ma. The Minobu Mountains and possibly the adjacent mountains could be uplifted by the collision of the Izu Block at ca 1 Ma. Mountain formation in the Izu collision zone is mainly controlled by the collisions of crustal blocks of the Izu-Bonin Arc and motional change of the Philippine Sea plate.
