ボーキサイト及礬土頁岩鑛床 -粘土類風化並堆積作用の地史的考察-
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概要
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A colloidal aluminosilicate complex with a given composition becomes a fixed deposit in a certain environment in the weathering crust on the earth's surface, as a non-dispersive isoelectric precipitate, according to the acidity of that environment., The writer proposes that its distribution in nature can be summarized, in a general manner, by "Isosials" or "Equal Silica-Alumina Molecular Ratio Lines"., It is controlled by meteorological factors and hence there is a regular harmony among different climatic zones, the fullest developed being a laterite profile in the tropics., A laterite profile, in the arrangement of its component minerals, resembles the profile of a low temperature hydrothermal alunite deposit., Although the alunitization is caused by the heat from the earth's interior, or is controlled by the energy of an entirely different source, the similarity is due to the fact that the elements of the chemical reactions, above and below the underground water table on the earth's surface, closely resemble each other., It is also quite natural that there is again a striking similarity between the stability fields of those minerals in the hydrothermal syntheses of silicates, as conducted by Noll and others, and the environments of the formation in the above two profiles in nature., In view of its position with regard to the "ISOSLALS" a bauxite is, no doubt, the product of an extreme weathering, hill tops or cliff edges on a level land and a tropical monsoon being the optimum for its formation., Stratigraphically, the bed of a redeposited laterite can be reckoned as an abnormal facies of a basal conglomerate., It is because the laterite is an end product of weathering on a level land., The lenticular rich ore bodies of the bando-ketsugan (aluminous shale) are channel deposits on a lake bottom, being comparable with the U, V and Cu bearing clay lenses in the "Red Beds" in the western US., The bando-ketsugan (aluminous shale) and the Koshitsu-nendo (flint clay) beds, are reworked laterite materials in the Upper Paleozoic age in N., China, S., Manchuria and Korea., They reach 20m in their aggregate thickness in most coal-fields, and are the largest of all known ore beds of kaolinite and aluminous hydroxide in the world., This is due to the fact that this region, in the Upper Paleozoic era, formed an extensive sedimentary basin of an epeirogenic type with the gentlest crustal movement in the world., In contrast, the Mesozoic era, in the same region, witnessed the formation of many local sedimentary basins of an orogenic type., The character of those crustal movements accounts for the distinct types of coal ash and the composition of clay colloids deposited in both basins., That is, the coal ash, in the sedimentary basin of an orogenic type, are characterised by the montmorillonite series or the clay minerals in the juvenile stage of evolution, while those in the sedimentary basin of an epeirogenic type, by the kaolinite series or those in the mature stage of evolution., Further, the laterite materials of the bando-ketsugan are clay minerals in the senile stege, or the ones which have the least chance both of formation and preservation in the region of an orogenic movement., The writer, in the present paper, proposes the term and concept of "Isosials" which, representing a regular arrangement of soil colloids in the generalized soil profile covering the Frigid and Tropical zones, point to the "evolution" of clays., He has also illustrated that the types of coal ashes, when represented by clay minerals in different stages of the evolution, reflect different types of crustal movements to which the coal basins are due.,
- 日本地質学会の論文
- 1950-06-25