Characterization of Water Conducting Fracture and their Long-term Behavior in Deep Crystalline Rock :

ISHIBASHI Masayuki, ANDO Tomomi, SASAO Eiji, YUGUCHI Takashi, NISHIMOTO Shoji, YOSHIDA Hidekazu

doi:10.5110/jjseg.55.156

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Other Title

深部結晶質岩における割れ目の形成・充填過程と透水性割れ目の地質学的特徴
深部結晶質岩における割れ目の形成・充填過程と透水性割れ目の地質学的特徴 : 土岐花崗岩を例として
シンブケッショウシツガンニオケルワレメノケイセイ・ジュウテンカテイトトウスイセイワレメノチシツガクテキトクチョウ : トキハナオカガンオレイトシテ
Characterization of water conducting fracture and their long-term behavior in deep crystalline rock: A case study of the Toki granite
―土岐花崗岩を例として―
A Case Study of the Toki Granite

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Long-term history of water conducting fracture is key issue to evaluate deep geological environment for geological disposal of high-level radioactive waste. Thus, we carried out study on the geological features and the long-term behavior of water conducting fractures based on the data obtained at －300 m levels in the Mizunami Underground research laboratory (MIU), central Japan.<br> Total 1,670 fractures were described in underground gallery at the －300 m levels. Water conducting fractures occupy about 11 % of all fractures. They are divided into two groups： grout filling fractures and low inflow-rate fractures. The former is filled with calcite without conspicuous host rock alteration around fractures. The letter possessed similar geological character with the sealed fractures which are not acted as flow-path.<br> The geological character of fracture filling and host rock alteration around fractures indicate the history of three stages; a) intrusion and emplacement of host granite, b) fracture filling at hydrothermal event, and opening and/or elongation during exhumation, c) fracture filling at inflow of meteoric water.<br> In conclusion, the present water conducting fractures were formed by opening or elongation of pre-existed fractures, which were filled at the hydrothermal event, at the time of exhumation.

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Journal of the Japan Society of Engineering Geology

Journal of the Japan Society of Engineering Geology 55 (4), 156-165, 2014

Japan Society of Engineering Geology

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