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）富士火山火山喷射的比较岩石学研究：我们检查了3000ybp Omuroyama侧面喷发的岩石学特征，AD.864 Jyogan爆发和AD。 1707年，Hoei爆发了解富士火山的喷发方式与弹射器晶体质地之间的关系。斜长石表晶和微晶的组成分区告诉我们在岩浆upise和喷发期间的含水矩阵岩浆的脱气和补给过程。 Omuroyama喷发的3000年具有子层型碎屑秋季沉积物，其中含有有限的斜长石麦微体晶体，这表明由于喷发前的水脱气而导致的岩浆结晶的时间仅限。 AD.864爆发产物经常在边缘附近进行反向分区20-30％，表明岩浆在有效喷发前通过氢磁岩层补充了脱水的浅层岩浆。（2）在杂志上进行混合的效果更多，以使MAGMAS的效果进行了更多的混合： 数字。先前的实验（EG。Blake和Campbell，1986年）仅检查了雷诺数高的混合条件。岩浆口袋的存在会增加层状环流的不稳定性，因为重力增加了抗粘性力。结果表明，当无量纲参数i（=粘性力/重力力）小于0.1时，流动不稳定性发生。对最终成员岩浆状况的分析表明，流动不稳定性发生在未沸腾的火山下方的岩浆袋中。（3）水含量和火山喷射的水合：我们检查了AD.1783的Andesitic-Ryolical玻璃。 1108和妈妈火山的13KA BP喷发产品。 AD.1783和AD.1108弹出的水含量为03-0.7 wt％，而13KA喷射的水含量为15-4 wt％。 In back-scattered electronic 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 thoiite: Crystal phases are mainly augite and plagioclase with minor amount of olivine.爱因斯坦 - 罗斯科山麦克斯方程几乎很好地解释了含晶体的岩浆的相对粘度，表明各向异性晶体形态的效果与晶体尺寸分配的效果相抵消。晶体相也由橄榄石量的橄榄石和斜长石组成。含晶体岩浆的相对粘度大于爱因斯坦 - 罗斯科山麦尔什方程的值3-5，这可能是由于MORB电荷中斜长石的较高长宽比。较少的

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