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

Abstract

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.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.