Eruption mechanisms and mineral textures of the ejecta

喷发机制和喷射物的矿物结构

• 批准号: 18540474
• 负责人: SATO Hiroaki
• 金额: $ 2.48万
• 依托单位: Kobe University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2006
• 资助国家: 日本
• 起止时间: 2006 至 2007
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18540474/
• 关键词: crystal textures; viscosity; plagioclase; crystal size distribution; magma mixing; analogue experiments; water content of eiecta; Asama volcano; 結晶組織; 富士火山; 元素分配; 結晶累帯構造; Einstein-Roscoeの式

(1) Comparative petrological study of volcanic ejecta of Fuji volcano: We examined petrographic features of the 3000ybp Omuroyama flank eruption, AD.864 Jyogan eruption, and AD. 1707 Hoei eruption to understand the relations between the mode of eruptions and crystal textures of the ejecta at Fuji volcano. Compositional zoning of plagioclase phenocryst and microphenocryst tells us the processes of degassing and recharge of hydrous aphyric magmas during the magma uprise and eruptions. The 3000 yr by Omuroyama eruption had subplinian pyroclastic fall deposit which contains limited amount of plagioclase microphenocryst, suggesting only limited time for crystallization of magmas due to degassing of water just before the eruption. The AD.864 eruption products 20-30% of plagioclase phenocryst often with reverse zoning near the rim, indicating magma replenishment of degassed shallow magma by hydrous aphyric magmas just before the effusive eruptions.(2) Analogue experiments of the effect of mag … More ma pocket on the mixing of magmas: This experiment intends to examine the mixing processes of two magmas at low Reynolds number. Previous experiments (e g. Blake and Campbell, 1986) only examined the mixing conditions at high Reynolds number. Presence of a magma pocket increases the instability of laminar annular flow because of the increase of gravitational force against viscous force. It is shown that flow instability occurs when the dimensionless parameter I (=viscous force/gravitational force) is less than 0.1. Analyses of the condition of end member magmas indicate that flow instability occurs in a magma pocket beneath Unzen volcano.(3) Water content and hydration of volcanic ejecta: We examined andesitic-rhyolitic glasses of the AD.1783, AD. 1108, and 13ka bp eruption products of Mama volcano. Water contents are 03-0.7 wt % for AD.1783 and AD.1108 ejecta, whereas they are 15-4 wt% for 13ka ejecta. In back-scattered electron images of 13ka volcanic glasses, we observed clear hydration front in the core of the vesiculated bubble wall glass, suggesting that high water content of the old deposits are affected by secondary hydration of the glass.(4) Viscosity measurement of subliquidus magmas:A Kilauea thoeiite: Crystal phases are mainly augite and plagioclase with minor amount of olivine. The relative viscosity of the crystal-bearing magma is almost well explained by the Einstein-Roscoe-Marsh equation indicating that the effect of anisotropic crystal morphology is counterbalanced by the effect of crystal size dispersion.B: MORB tholeiite: An ODP Leg 206 MORB sample is used for the viscosity measurement. Crystal phases also consist of augite and plagioclase with mirror amount of olivine. The relative viscosity of the crystal-bearing magma is larger than the values of Einstein-Roscoe-Marsh equation by a factor of 3-5, which may be due to the higher aspect ratio of the plagioclase in the MORB charge. Less

（1）富士火山火山喷发物的岩石学比较研究：我们研究了3000ybp大室山侧翼喷发、公元864年城岩喷发和公元1707年丰荣喷发的岩石学特征，以了解喷发模式与晶体结构之间的关系。富士火山喷出物的斜长石斑晶和微斑晶的组成带。告诉我们在岩浆上升和喷发过程中含水非非晶岩浆的脱气和补给过程。大室山喷发的 3000 年有亚普林期火山碎屑沉积物，其中含有有限数量的斜长石微斑晶，这表明由于脱气而使岩浆结晶的时间有限。 AD.864喷发前的水含量为20-30%。斜长石斑晶在边缘附近经常出现反向分带，表明在喷发前，含水非非晶岩浆对脱气的浅层岩浆进行了岩浆补充。(2) 磁囊对岩浆混合影响的模拟实验：本实验旨在检查两种岩浆在低雷诺数下的混合过程（例如 Blake 和 Campbell，1986）仅检查高雷诺数下的混合条件。岩浆囊的存在会增加层流环空流的不稳定性，因为重力对抗粘性力的作用会增加。结果表明，当无量纲参数 I（=粘性力/重力）小于 0.1 时，就会出现流动不稳定。对端元岩浆状况的分析表明，云仙火山下方的岩浆囊中存在流动不稳定。(3)火山喷出物的含水量和水化：我们检查了AD.1783、AD.1108 和 13ka bp 的 Mama 火山喷发产物的含水量为 03-0.7 wt%，而 AD.1783 和 AD.1108 喷射物的含水量为 15-4 wt%。在 13ka 火山玻璃的背散射电子图像中，我们观察到清晰的情况。水化前沿出现在多孔泡壁玻璃的核心，表明老矿床的高含水量受到了玻璃二次水化的影响。(4)液下岩浆的粘度测量：基拉韦厄斜长石：晶相主要为辉石和斜长石含有少量橄榄石的含晶体岩浆的相对粘度几乎可以用爱因斯坦-罗斯科-马什方程很好地解释，表明：各向异性晶体形态的影响被晶体尺寸分散的影响所抵消。B：MORB 拉斑斑斑玄武岩：ODP Leg 206 MORB 样品用于粘度测量，晶相也由辉石和斜长石组成，其中含有大量的橄榄石。含晶体岩浆的粘度比爱因斯坦-罗斯科-马什方程的值大3-5倍，这可能这是由于 MORB 装料中斜长石的长径比较高。

项目成果

富士火山大室山噴出物の岩石学的研究.

富士火山大室山喷射物的岩石学研究。

• 发表时间: 2007
• 作者: Hanyu T.;Tatsumi Y.;Nakai S.;Shibata T.;Yoshida T.;御堂丸直樹・佐藤博明・藤井敏嗣
• 通讯作者: 御堂丸直樹・佐藤博明・藤井敏嗣

FeO*-Al2O3-TiO2- rich rocks of the Tertiary Bana igneous complex, west Cameroon

喀麦隆西部第三纪巴纳火成岩杂岩中富含 FeO*-Al2O3-TiO2 的岩石

• 发表时间: 2008
• 期刊: Resource Geology (in press)
• 作者: Kuepouo;G.;Sato;H.;Tchouankoue;JP;Murata;M
• 通讯作者: M

I atmosphere melting experiments on the basatic Magmas of Oginosen volcanoUniv

荻野泉火山基性岩浆的大气熔化实验大学

• 发表时间: 2007
• 作者: Honma;U;Sato;H
• 通讯作者: H

Juxtaposition of adakite, boninite, high-Ti02 and low-Ti02 basalts in the Devonian southern Altay, Xinjiang, NW China.

新疆阿勒泰地区泥盆系南部埃达克岩、栉长岩、高Ti02和低Ti02玄武岩的并置.

• 发表时间: 2006
• 期刊: Journal of Asian Earth Sciences 28
• 作者: Niu;HC;Sato;H;Zhang HX 他5名
• 通讯作者: Zhang HX 他5名

Petrologial studies on the eruption Products of the Omuroyama flank cone, Fuji volcano

富士火山大室山侧锥喷发产物的岩石学研究

• 发表时间: 2007
• 作者: Midomaru;N.;Sato;H.;and Fujii;T
• 通讯作者: T