那須茶臼岳火山噴出物の全岩主化学組成 ―分析データ114個の総括―
Year: 2016
Type: article
Abstract: Whole-rock major element chemistry for the eruptive products of Nasu-Chausu volcano, northeast Japan is studied based on newly obtained 114 analytical data. The Nasu-Chausu volcano is a small to intermediate scale polygenetic composite volcano with areal dimension of 3×1.5km, which is a young volcano and active since 16ka. The volcanic rocks of Nasu-Chausu volcano are calc-alkaline low- to medium-K andesite. The SiO₂ content ranges from 55 to 65wt.％. The major elemental chemical compositions of eruptive products of the Nasu-Chausu volcano show nearly the same compositional trends on silica variation diagrams, except for those of the Osawa pyroclastic flow deposit (OSFL), eastern lava 2 (LE2), older lava dome (OD), Ozawa debris avalanche deposit (OZDA) and southern lava (SL). The whole-rock major elemental chemical compositions of LE2 and OD are similar and probably the products of the same eruptive episode. It is concluded by the field geological evidences and whole-rock major element chemistry that the eruptive history of lavas of Nasu- Chausu volcano comprises following six stages: Stage 1 (OSFL and related lava), Stage 2 (eastern lava 1 (LE1)), Stage 3 (LE2 and OD), Stage 4 (LS), Stage 5 (eastern lava 3 (LE3), eastern lava 4 (LE4), northern lava (NL), Chausu pyroclastic rocks 1 (CP1), Chausu pyroclastic rocks 2 (CP2) and Chausu pyroclastic rocks 3 (CP3)), and Stage 6 (summit lava dome (SD) and western lava (LW)). The lavas of Stage 5 show unique appearance and are inferred to be clastogenic, probably produced by a kind of Vulcanian to Stromborian eruptions with unique mode.
Authors: Masaki,TAKAHASHI, Yoichi,NAKAJIMA, Maya,YASUI, Tatsuo,KANAMARU, Akira,NAGUMO
Language: Japanese
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7145736053