青函トンネルの粘土鉱物 (第1報) : 北海道方について

概要

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The Seikan Tunnel, connecting Honshu with Hakkaido by railway, is the longest undersea tunnel in the world, upon completion it will pass cross the Tsugaru Straits Undersea. The Straits is underlain by volcanic, pyroclastic, and sedimentary rocks (the Fukuyama, Kunnui, Yakumo, and Kuromatsunai formations) of Neogene age. Clay mineralogical investigation was carried out on 70 core samples obtained from the pilot and service tunnels at the Hokkaido side of this tunnel by means of X-ray diffraction technique, thermal analysis, and electron microscopy. Some of the core samples were observed under petrographic microscope. It is found that these core samples contain di-octahedral and tri-octahedral smectites. chlorite, interstratified mineral of chlorite/smectite, and mica clay mineral as clay minerals. Among them, di-octahedral smectite occurs most dominantly and is widely distributed in pyroclastic and sedimentary rocks, whereas tri-octahedral smectites found only in basalt. The lower part (Kn-2) of the Kunnui formation is characterized by the presence of interstratified mineral of chlorite/smectite. This is in good agreement with the results obtained by Yoshimura and Kawahara et al. In addition to clay minerals, zeolites such as clinoptilolite, analcime, and laumontite are found. Regarding zeolites, characteristic distribution enough to classify the formations is not recognized.
日本粘土学会の論文
1982-06-25