書誌事項
- タイトル別名
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- Conduit Magma Process of Miyakejima Volcano Inferred from Basaltic Juvenile Materials in the Products of the Small Ash Eruptions during the Continuous Degassing
- ミヤケジマ カザン ノ レンゾク ダツガス ニ トモナウ ショウフンカ フンシュツブツ ニ フクマレル ゲンブガン ホンシチブツ カラ スイソク スル カドウナイ マグマプロセス
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The Miyakejima volcano repeats small ash eruptions from the degassing vent opening inside the A.D. 2000 caldera. The juvenile glassy fragments in the tephra indicate that the basaltic magmas with primitive composition are ascending in the open conduit and degassing at the shallow depth. We examined the representative 12 tephra samples erupted between October 2001 and July 2010, and found the juvenile glassy fragments with basaltic character. Their fresh surfaces and free from alteration or weathering indicate that these glassy grains are juvenile materials. The glassy fragments occupy less than 1 vol.% of the tephra, that mainly consists of the fragments of lavas and pyroclastics derived from the previous edifice. The juvenile fragments consist of volcanic glass with pale-brownish color and euhedral crystals of plagioclase, clinopyroxene and olivine up to several tens micrometers across. Larger crystals of plagioclase and olivines more than 100 micrometers are also contained as microphenocryst. The range of the Fo contents of the olivine microphenocrysts in the glassy fragments is 73-83, which is higher than that of the phenocryst olivine in the basaltic bombs erupted during the August 18, 2000 eruption and similar to that of the olivine phenocrysts derived from the primitive basaltic magma, indicating that the continuous degassing since the A.D. 2000 eruption has been driven by the basaltic magmas with primitive character. The low sulfur and chlorine contents in the groundmass glass indicate the degassing under low pressure.
収録刊行物
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- 火山
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火山 55 (6), 241-250, 2010
特定非営利活動法人 日本火山学会
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詳細情報 詳細情報について
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- CRID
- 1390001204303186816
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- NII論文ID
- 110008441078
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- NII書誌ID
- AN10512786
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- ISSN
- 21897182
- 04534360
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- NDL書誌ID
- 10983783
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- 本文言語コード
- ja
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- データソース種別
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- JaLC
- NDL
- CiNii Articles
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- 使用不可