Jun-ichi Masui

Chemical and mineralogical studies on volcanic ashes I. Chemical composition of volcanic ashes and their classification

Abstract Air-borne pyroclastic materials originating from various volcanoes were collected in Hokkaido, Tohoku, Kanto, and Kyushu, and were used for a total elemental analysis. It was shown that the silica content of the materials closely correlated with the various contents of Al2O3, Fe2O3+FeO3, Fe3, MgO, CaO, Na2O, TiO2, and MnO, and so serves as useful basis for classifying the materials. On the basis of the silica content of the air-borne pyroclastic materials, the present authors classified the materials as follows; Comparison of the average chemical composition of common Japanese volcanic rocks with the analytical data of the present paper indicated that there is no significant difference in chemical composition between the air-borne pyroclastic materials and the rocks.

Amorphous clay minerals of recent volcanic ash soils in hokkaido (ii)

Abstract In the previous study (1), it was shown that the size-fractions finer than 2 μ of the soil samples were abundant in siliceous amorphous materials. These materials are more siliceous in the specimens of the A horizons than in the C and tend to become more siliceous with increase of particle-size. Discrete amorphous silica is present in all the size-fractions finer than 2 μ and its amount is considerably greater in coarser clay fractions. Since the proportions of coarser clay fractions are greater in the whole clay fractions, it is considered that the amorphous silica of the coarser clay fractions play a significant role in determining the properties of all of the amorphous clay minerals contained. Amorphous silica exists not only in the fractions finer than 2 μ, but also in the fractions coarser than 2 μ, even in the fine sand fractions of the A horizons.

Montmorillonite in a Volcanic Ash Soil

Abstract Many kinds of volcanic ash soil distributed in Japan are usually high in humus content, consequently very dark or nearly black in color, light, loose and very friable. They have also a marked allitic property owing to the relatively large contents of allophane and aluminium hydrous oxide which strongly bind with phosphate ion.

CHEMICAL AND MINERALOGICAL STUDIES OF VOLCANIC ASHES : II.Relationships between Rock Types and Mineralogical Properties of Volcanic Ashes

Abstract The relationships between rock types and mineralogical properties of volcanic ashes were investigated using many volcanic ash samples from different volcanoes. The heavy mineral fraction was dominated by two pyroxenes and ferromagnetic minerals In almost all the felsic and Intermediate volcanic ashes. Therefore, It was difficult to determine the rock types of felsic and intermediate volcanic ashes according to their heavy mineral composition. It was assumed that the presence of a large quantity of hornblende was related to the origins of the volcanic ashes. On the other hand, the predominant mineral in the heavy mineral fraction of mafic volcanic ashes was volcanic glass (refractive index about 1.59), followed by olivine. The refractive indices (γ) of plagioclases and orthopyroxenes were 1.553–1,570 and 1.703–1.715 in the felsic volcanic ashes, 1.558–1.580 and 1.705–1,715 in the intermediate ashes, and 1.565–1.576 and 1.697–1.705 in the mafic ashes, respectively. These results indicate the diffic...

COPPER AND ZINC IN VOLCANIC ASH SOILS

Abstract Recently copper and zinc deficiencies in upland crops have often been found on the volcanic ash soils which occupy about a half of the total area of upland field in Japan. Since it is supposed that much more chemical fertilizer will be used for upland crops under intensive farming in the future, it is likely that the problem of minor element deficiencies in upland crops will become more serious.

Crystalline clay minerals of the soils derived from recent volcanic ashes in Hokkaido, Japan: II. 2:1 Type Clay Minerals

Abstract In the previous study on clay minerals in the soils derived from recent volcanic ashes, it has been shown that expanding layer silicates with more or less interlayer-Al are found in large amounts among crystalline clay minerals, and that chlorite, illite and possibly kaolin minerals are found in small amounts (1). Montmori11onite shows a tendency to be dominant in the soils of the younger group and to be less Alinterlayered, However, vermiculite tends to increase, and both montmorillonite and vermiculite become more Al-interlayered in the soils of the older group. The purpose of the present report is to investigate 2: 1 type clay minerals, chiefly expanding layer silicates.

Clay mineral with random interstra tification in volcanic ash in Japan

Abstract The volcanic ashes derived from recent volcanoes are widely distributed in Japan from Hokkaido to Kyushu. Therefore the study on the weathering of these materials is very important from the pedological standpoint.