Brief introduction to Tsukinuno bentonites

The deposit is composed of 35 bentonite beds of which 9 are thicker than 1 m. These bentonite beds are large-scale stratified deposits, that occur today in a fold structure, meaning that the same bentonite bed can be found at various depths.

Mine area
Plan figure and cross section of the Tsukinuno bentonite deposit after Kobayashi and Itoh (1992).

Tsukinuno bentonites are composed of mainly Na-montmorillonite, some with significant amounts of quartz. Also other minerals, such as feldspars, illite, calcite and zeolite can be found in these bentonites. Calcite occurs in some of the beds as nodules (or concretions), with sizes up to 10’s of cm.

Bentonite beds were formed during the Middle Miocene (sub-epoch that occurred ~16 to ~12 million years ago) and occur within a brown hard shale rock type (also referred to as mud shale).

Tsukinuno bentonites have been formed by diagenetic alteration from the volcanic ash deposited on the sea floor (see image by KIC below). Also hydrothermal bentonites occur in Japan elsewhere.

For more details please see the selected list of references below.

bentonite formation.jpg

Tsukinuno mine and natural bentonite reports and papers

Ishida, H. (1995). Selected analytical data from Unpubl. PhD Thesis, Waseda University, Tokyo, Japan (in Japanese).

Ito, D., Komine, H., Morodome, S., Sekiguchi, T. & Miura, G. (2017a). Evaluating  the influence  of  cementation  on  the  physical  properties  of  buffer  material  by  measuring  the  swelling  characteristic and hydraulic conductivity of bentonite ore. The 12th Proceedings of the third Japan National Symposium on Environmental Geotechnology. 547-552 (in Japanese).

Ito, D., Komine, H., Morodome, S., Sekiguchi, T. & Miura, G. (2017b). Quantitative evaluation of cementation in buffer material based on swelling pressure characteristic of bentonite raw ore.  The 52nd Geotechnical Research Presentation, 2067-2068 (in Japanese).

Ito, D., Komine, H., Kenkyu,T., Sekiguchi, T. & Miura, G. (2017c). Influence of consolidation of bentonite ore on permeability coefficient measurement by high pressure consolidation experiment. The 72nd Annual Scientific Lecture of the Japan Society of Civil Engineers VII-056, 111-112 (in Japanese).

Ito, M., Okamoto, M., Shibata, M., Sasaki, Y., Danbara, T., Suzuki, K. & Watanabe, T. (1993). Mineral composition analysis of bentonite. PNC Technical Report TN8430 93-003, JAEA, Tokai, Japan (in Japanese).

Ito, M., Okamoto, M., Suzuki, K., Shibata, M. & Sasaki, Y. (1994). Mineral composition analysis of bentonite. J. At. Energy Soc. Japan 36, 1055-1058 (in Japanese).

Jasmund, K. & Lagaly, G. (2013). Tonminerale und Tone: Struktur, Eigenschaften, Anwendungen und Einsatz in Industrie und Umwelt. Springer-Verlag, Berlin, Germany (in German).

Kamei, G., Sato, H. & Shibata, M. (1995). A  Natural Illustration of Long-Term Diffusion of Water in Bentonite. Bentonite Bed which Has Kept in Contact with Groundwater for 29 Years. J. At. Energy Soc. Japan 37, 624-627 (in Japanese).

Kon, Y., Takagi, T., Hirata, T., Mogi, K. & Ito, M. (2009). Geochemistry and geochronology of zircon from bentonite, Tsukinuno Mine, Yamagata, Japan. Abstract in the Proc. 116th Annual Meeting Geol. Soc. Japan. ISSN : 1348-3935 (in Japanese).

PNC (1994). Groundwater chemistry of the Tsukinuno mine. PNC Technical Report TN8420 94-007. JAEA, Tokai, Japan (in Japanese).

Saji, S., Ito, M., Shibata, M., Jintoku, T. & Isogai, T. (2005). Depth Trend of Chemical Characteristics of Bentonite Deposit in Contact with River Water. Sampling and Analytical Results. JNC Technical Note TN8400 2005-017, JAEA, Tokai, Japan (in Japanese with English abstract).

Sato, H. (2011). Quantification of Exchangeable Cations in Interlayer of Tsukinuno Sodium-Montmorillonite. MRS Online Proceeding Library Archive 1193. DOI 10.1557/PROC-1193-529 (NB copy requested from Sato-san)

Takagi, T. (2005).  Bentonite in Japan – Geology and Industries. Open file report of the Geological Survey of Japan, No. 425, pp1-13. AIST, Tsukuba, Japan.

Yamaya, K. (1984). Tsukinuno Mine (description). J. Mining Materials Inst. Japan 100, 978-980 (in Japanese with English abstract).

Yui, M., Sasaki, Y., Shibutani, T. & Sato, H. (1994) An approach to understanding bentonite-water interaction and nuclides migration in bentonite. The Atomic Energy Society of Japan.   Radioactive waste research 1 (1), June, 1994 (in Japanese).