Mechanism of the formation of volcanic ashes from Sakurajima Volcano, Japan, and its influences to the environments

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Authors:Oba, Noboru; Tomita, Katsutoshi; Yamamoto, Masahiko; Inoue, Kozo; Nakamura, Toshifumi; Ishii, Toshihiko; Kiyosaki, Seiichi
Author Affiliations:Primary:
Kagoshima Univ., Inst. Earth Sci., Kagoshima, Japan
Other:
Hiroshima Univ., Japan
Shoko Junior High Sch., Japan
Volume Title:Kagoshima Daigaku, Rigakubu Kiyo Chigaku, Seibutsugaku Reports of the Faculty of Science, Kagoshima University: Earth Sciences and Biology
Source:Kagoshima Daigaku, Rigakubu Kiyo Chigaku, Seibutsugaku = Reports of the Faculty of Science, Kagoshima University: Earth Sciences and Biology, Vol.17, p.1-22. Publisher: Kagoshima Daigaku, Rigakubu, Kagoshima, Japan. ISSN: 0385-4019
Publication Date:1984
Note:In English. 11 refs.; illus. incl. 8 tables, 1 plate
Summary:Volcanic ashes erupted out from Sakurajima Volcano, Kagoshima Prefecture, were classified into four types on the basis of the mass colour, constituent minerals, their grain shape, chemical composition and refractive index: black ash, red ash, black ash having characteristics of the former two ashes, and white ash. The black ash which contains irregular shaped-matrix grains came from explosively crushed lavas within the volcanic vent. The red ash is characterized by abundant rounded matrix grains, high Fe2O3 content, wide range of refractive index in matrix glass, and the presence of alpha-cristobalite, gypsum and anhydrite, and may be a mixture of pre-existing and recent volcanic ash. The white ash contains abundant colourless and irregular shaped-grains and vesiculated matrix glass, and was probably blown up in a vesiculated state accompanying adiabatic expansion through a narrow volcanic vent successively and immediately from the magma. The chemical composition data fall in the field of the calc-alkali rock series on the SiO2-total FeO/MgO diagram. They differ from those of volcanic rocks and bombs of Sakurajima Volcano because of the presence of gypsum in the volcanic ashes. [Y.A.]
Subjects:Classification; Composition; Crystals; Differential thermal analysis; Genesis; Grain size; Gypsum; Igneous rocks; Mechanism; Pyroclastics; SEM data; Sulfates; Textures; Volcanic ash; Volcanic rocks; Volcanoes; Volcanology; X-ray data; Asia; Far East; Japan; Kagoshima Japan; Kyushu; Sakura-jima
Abstract Numbers:90M/3545
Record ID:1985086029
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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