| Project/Area Number |
59470042
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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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 | Akita University |
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Principal Investigator |
ISHIHAWA Yohei professor, Mining College, Akita University, 鉱山学部, 教授 (00113887)
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| Co-Investigator(Kenkyū-buntansha) |
MARUYAMA Takahiko assistant professor, Mining College, Akita University, 鉱山学部, 助教授 (60006682)
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| Project Period (FY) |
1984 – 1986
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| Project Status |
Completed (Fiscal Year 1986)
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| Budget Amount *help |
¥6,600,000 (Direct Cost: ¥6,600,000)
Fiscal Year 1986: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1985: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1984: ¥4,100,000 (Direct Cost: ¥4,100,000)
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| Keywords | Kuroko deposit / Vein-type deposit / Hydrothrmal alteration / Superposed alteration / Uwamuki Kuroko deposit / Kosaka mine / Fukazawa Kuroko deposit / Ezuri Kuroko deposit / 北鹿地域 |
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| Research Abstract |
The Ezuri Kuroko deposit, located nearly at the central part of the Hokuroku district, Akita Prefecture. In the area host volcanic rocks were hydrothermally altered during Kuroko mineralization and vein-type mineralization of the younger stage.
The following two kind of hydrothermal alteration envelopes are reconginized in the volcanic rocks. (1) Hydrothermal alteration related to the kuroko mineralization at the earlier stage. The cenrtal part of the deposit is characterized by the sericite and K-feldspar assemblage. The alteration zones show gently crossed relationships to the formation boundaries with marshroom-like shape. (2) Hydrothermal alteration related to the vein-type mineralization at the later stage. The central part of the deposit is characterized by the pyrophyllite and Mg-chlorite is present around the quratz porphyry intrusion. The alteration zones show steeply cross cutting relationships to the formation boundaries with funnel-like shape.
The latter is superposing upon the former, especially around the Iwagami vein-type deposit. These facts mentioned above suggest that the pyrophyllitization and mineralization of the Iwagami vein-type deposit took place at the near surface of land during the late Miocene hydrothrmal activity with quratz porphyry intrusion. Predominated distribution of the Mg-chlorite is around the quratz porphyry may indicate that the magnesium fixation have been promoted by the hydrothrmal solutions with high ionic activity of magunesium at the later stage.
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