口永良部島における堆積火山灰の風化と粘土鉱物の生成 (1)
書誌事項
- タイトル別名
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- The Weathering State of Volcanic Ashes and Clay Mineral Formation at Kuchinoerabujima Island
抄録
Kuchinoerabujima is a small volcanic island which is situated at Tokara Islands, southern part of Kyushu, Japan. And the climate of the island, one of the factors affecting weathering, is warm and very wet.<BR>In the island, alteration phenomena of the sedimentary volcanic ashes which belong to augite-hyperthene andesite were observed. And the sequence of changes of the sediments from upper to lower layer was studied mineralogically and chemically, and following results were obtained.<BR>1) At surface layer, amorphous silico-alumina and hydrous sesquioxides as secondary minerals are detected. The amount of those clay-size materials is very little in quantity.<BR>2) In the second layer, the decomposition of plagioclase obviously proceeds and allophane, halloysite and gibbsite are formed. The grain size of those minerals is generally very small except gibbsite, which cementizes the particles of volcanic ashes and grows about 10-20μin size.<BR>3) In the third layer which developes at the part of 2-3 m from the surface (vertical width 0.5-2 m), halloysite, illite, 14Å-mineral and iron hydroxide are found. This layer is very clayey and is dark-brownish in color and also it represents an illuvial zone. The amounts of Si02, Fe203, K20 and Mg0 of the clay separated from this layer are relatively rich compared with the components of the clays obtained from other layers.<BR>4) Under the third layer, allophane and gibbsite are mainly formed when the layer is composed of coarse particles. And as the layer becomes more clayey, halloysite content is more rich. The molar ratio, Si02/Al203, of the clay is about 2.
収録刊行物
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- 粘土科学
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粘土科学 14 (1), 20-33, 1974
一般社団法人 日本粘土学会
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詳細情報 詳細情報について
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- CRID
- 1390282679088813440
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- NII論文ID
- 130004307281
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- ISSN
- 21863563
- 04706455
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- データソース種別
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- JaLC
- CiNii Articles
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- 抄録ライセンスフラグ
- 使用不可