Clay mineralogical properties of volcanic ash soils in Hokkaido, Japan
2003
Nizamidin, K. (Rakuno Gakuen Univ., Ebetsu, Hokkaido (Japan)) | Nanzyo, M. | Amano, Y. | Mizuno, T. | Yoshida, H. | Mizuno, N.
Clay mineral composition of volcanic ash soils distributed in Iburi, Oshima-Hiyama, Tokachi, Kushiro-Nemuro and Abashiri subprefecture, Hokkaido, Japan was examined and the following results were obtained. 1) The major parent material of the coarse volcanic ash soils near Mt. Tarumae of Iburi subprefecture is the Ta-a tephra and their clay content and noncrystalline materials content was small. The soils derived from Ta-b tephra, several hundred year old, basically showed properties similar to those from Ta-a tephra although the former contained a small amount of illite and chlorite. The soils derived from Ta-c, d tephras, several thousand years old, showed a high content of noncrystalline materials, chloritized vermiculite and chlorite. The lower horizon soil derived from Ta-d tephra contained more than 20 % of allophane. 2) The volcanic ash soils distributed in the Tokachi subprefecture, far from the Mt. Tarumae, are finetextured and showed a high content of allophane irrespective of the age of tephra. The soils derived from Ta-b tephra sometimes contained a small amount of illite. The soils derived from Me-a tephra contained illite at the level of + - + + . 3) The clay fraction of soils derived from Us-a, b tephras, whose source volcano is Mt. Usu consisted mainly of smectite. The allophane content of these tephras was low. 4) The volcanic ash soils in the Abashiri subprefecture were derived mainly from Ta-a, Me-a, Km-a, and Ma-f and these soils contained a high amount of allophane. The content of chlorite and kaoline minerals was small. 5) The soils derived from older tephras than several thousand years contained illite and chlorite as well as allophane. 6) The low content of 0.1 M HCl-extractable Cu was attributed more to noncrystalline materials than to humus after regression analyses.
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