| Project/Area Number |
02640618
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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 | Hokkaido University |
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Principal Investigator |
YUI Shunzo Hokkaido Univ., Fac. Sci., Prof., 理学部, 教授 (10006637)
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| Co-Investigator(Kenkyū-buntansha) |
TUCHIYA T Hokkaido Univ., Fac. sci., Tech. Officer, 理学部, 教務職員 (80088848)
MATSUEDA H Hokkaido Univ., Fac. sci., Assoc. Prof., 理学部, 助教授 (20108921)
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| Project Period (FY) |
1990 – 1992
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| Project Status |
Completed (Fiscal Year 1992)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1992: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1991: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1990: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Keywords | Akaiwa, Otaru / Asari, Otaru / Acid sulfate alteration / Alunite / Miocene mineralization / K-Ar age / Migration of hydrothermal activity / 酸化とfs_2の変化 / トパ-ズ / alunite / natroalunite / 熱水の通路 / ダイアスポア / ズニ石 / 層状明礬石ー石英岩 |
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| Research Abstract |
The Sea of Japan side of the northern part of Japanese Islands forms a geologic province called the Green Tuff region where occur many ore mineralizations including gold-silverveins, kuroko deposits, and base metal veins. Otaru is located at the northern end of the Green Tuff region. Akaiwa district was main target of this project and Asari district, 13 km southeast of Akaiwa was also studied.
Mt. Shimo-akaiwa(279m above the sea) consists of intensely silicified volcanic rock (andesite?) containing alunite sporadically. At sea-shore, a silicified rock is surrounded by zoned alteration, argillic(mainly dickite) zone, illite(sericite)-smectite zone, chlorite zone, and propylite. The silicified rock contains diaspore crystals up to 2mm in size in the pore. In the argillic zone contains pyrophyllite and/or zunyite. This distribution of minerals seems to be resulted from oxidation of sulfur-containing acid hydrothermal solution.
"Breccia pipes" extend vertically. Inverse grading of silicified clast in a pipe suggests that it was formed by vigorous movements of ascending fluid. "Layered parts" are composed of fine-grained powders of quartz and alunite with normal size grading and seem to be formed in small hot lakes.
Geothermometry using homogenization temperature of fluid inclusion, sulfur isotope fractionation between sulfide and sulfate minerals, and mineral stability gave 200-250ﾟC.
Two K-Ar ages, 9.7*0.5 and 10.0*0.5 Ma have been obtaind from Akaiwa, and two, 6.1*0.6 and 4.8*0.4 from Asari, all for alunite. Considering younger ages reported from Toyoha, south of Asari, the hydrothermal activity migrated southwards since the Miocene age.
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