| Project/Area Number |
02640625
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
鉱物学(含岩石・鉱床学)
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| Research Institution | Toyama University |
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Principal Investigator |
UJIKE Osamu Toyama Univ., Faculty of Science, Aaaoc. Prof., 理学部, 助教授 (10176662)
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| Project Period (FY) |
1990 – 1991
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| Project Status |
Completed (Fiscal Year 1991)
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| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1991: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1990: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Strontium Isotope / Neodymium Isotope / Chubu District / Ueno Basaltic Rocks / On-take Volcano / Ryohaku Mountains / Mt. Kunimi-dake / Tojimbo / 玄武岩 / 同位体組成 / マグマ / マントル |
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| Research Abstract |
(1) The Ueno and On-take basaltic rocks
Ten samples of the Ueno basaltic rocks (2.7-0.9 Ma) have ^<87>Sr/ ^<86>Sr-0.7055-0.7070 and epsilon _<nd>-+3.3-1.1, and show no specific secular variation in isotpic compositions. The Ueno samples are higher in ^<87>Sr/ ^<86>Sr than basaltic rocks from the On-take volcano (<0.8 Ma) which lie within the mantle array on an epsilon _<nd>-^<87>Sr/ ^<86>Sr diagram. Because (1) the Ueno and On-take basaltic rocks were formed in the same area and (2) the difference in their ^<87>Sr/ ^<86>Sr cannot be ascribed to possible contamination by the crust, some episode (arrival of the leading edge of the subducting Philippine Sea plate?) seems to have occurred at 1+alpha Ma in the upper-mantle beneath central Japan.
(2) The Jizo-toge andesitic rocks
The Jizotoge andesitic rocks, formed at -2 Ma nearby the Ueno basaltic rocks, bear epsilon _<nd>-^<87>Sr/ ^<86>Sr relations similar to that of the Ueno basaltic rocks. The epsilon _<nd> and ^<87>Sr/ ^<86>Sr compositions of magmas generated at -2 Ma in this area seem to be insignificantly affected by the crustal material.
(3) Volcanic rocks from the Ryohaku Mountains and Fukui Prefecture
The epsilon _<nd>-^<87>Sr/ ^<86>Sr relations of volcanic rocks from the Ryohaku Mountains (Mts. Gankyoji-yama, Dainichiga-take, Kyoga-take and Bishamon-dake) and Fukui Prefecture (Mt. Kunimi-dake and Tojimbo) are largely similar to that of the Ueno basaltic rocks, but they show a greater scatter trending towards a higher ^<87>Sr/ ^<86>Sr and lower epsilon _<nd> direction.
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