Experimental Study of Magma Degassing Processes

岩浆脱气过程的实验研究

• 批准号: 06403003
• 负责人: KUSAKABE Minoru
• 金额: $ 13.95万
• 依托单位: Okayama University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (A)
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06403003/
• 关键词: Hydrous silicate glass; Infrared absorption spectroscopy; Molar absorption coefficient; Solubility of water; Magma degassing; Hydrogen isotopic ratio; ガス圧式高温高圧発生装置; 玄武岩メルト; 雲仙岳1991年噴火; 富士火山1707年噴火; 2価鉄濃度; ガラス包有物; H20濃度

(1)Infrared absorption spectroscopy of hydrous glasses of arc lava compositionsHydrous glasses of arc lava compositions (tholeiitic basalt, high-alumina basalt and dacite) were synthesized using a high pressure apparatus. The glasses were precisely analyzed for total water contents with hydrogen manometry, followed by FTIR analysis to obtain molar absorption coefficients of absorption bands at 2.8mum (molecular H_2O and OH stretching), 2.2mum (OH stretching and bending), and 1.9mum (stretching + bending of molecular H_2O).(2)Experimental determination of water solubility in basaltic melts at low pressureWater solubility in silicate melts is the most basic information in understanding the magma ascent and vesiculation. Using a gas-medium internal pressure apparatus, water-saturated basaltic melts of tholeiitic composition were prepared under 1200ﾟC and 10-80 MPa. The quenched glasses were analyzed for water contents to determine the water solubility. The data were combined with the lite … More rature values for higher pressures to obtain an empirical equation describing satisfactorily the water solubility in basaltic melts under a wide range of pressure, i.e., 10-1000 MPa.(3)Magma degassing and hydrogen isotopic variationsMagma degassing processes for the 1991-1992 Mt.Unzen volcano and 1707 Mt.Fuji volcano were considered on the basis of water contents and hydrogen isotopic rations of the glassy rocks. The Unzen magma had lost most of its water before dome formation. Degassing of water from the dome lava and underlying magma was controlled mainly by diffusion, resulting in increase in the D/H ratio as water content decreases. The scoria samples from the 1707 Fuji eruption showed the correlation that the D/H ratio increases as the Fe^<2+>/Fe^<3+> ratio decreases. This correlation was interpreted to indicate that significant loss of hydrogen took place at the time of eruption by reaction of water with Fe^<2+> in the magma. It was shown that the correlation between water contents and hydrogen isotopic variations can be used to evaluate the magma degassing processes. Less

（1）电弧熔岩成分水合玻璃的红外吸收光谱研究采用高压合成装置合成了电弧熔岩成分（拉斑玄武岩、高铝玄武岩和英安岩）水合玻璃。用氢压法精确分析了玻璃的总水含量，然后用FTIR分析获得了2.8 μ m（分子H_2O和OH伸缩）、2.2 μ m（OH伸缩和弯曲）和1.9 μ m（分子H_2O的伸缩+弯曲）吸收带的摩尔吸收系数。（2）低压下玄武岩熔体水溶解度的实验测定硅酸盐熔体的水溶解度是了解岩浆上升和泡状形成的最基本信息。利用气体介质内压装置，在1200 ℃和10-80 MPa条件下制备了水饱和的拉斑玄武岩熔体。分析淬火的玻璃的水含量以确定水溶解度。这些数据与精简版相结合 ...更多信息 较高压力下的温度值，以获得满意地描述在宽压力范围下玄武岩熔体中的水溶解度的经验方程，即，10-1000 MPa。（3）岩浆脱气和氢同位素变化根据玻璃质岩石的水含量和氢同位素比值，讨论了1991-1992年云仙火山和1707年富士山火山的岩浆脱气过程。Unzen岩浆在形成圆顶之前已经失去了大部分的水。水的脱气从圆顶熔岩和下伏岩浆主要由扩散控制，导致增加的D/H比作为水含量减少。1707年富士火山喷发的火山渣样品显示出D/H比值随Fe^<2+>/Fe^<3+>比值的降低而增加的相关性。这种相关性被解释为，在喷发时，由于水与岩浆中的Fe^<2+>反应，氢发生了显著的损失。结果表明，水含量与氢同位素变化之间的相关性可以用来评价岩浆的脱气过程。少

项目成果

S.Yamashita, Y.Tatsumi, and S.Nohda: "Temporal variation in primary magma compositions in the northeast Japan Arc" Island Arc. Vol.5 (in press). (1996)

S.Yamashita、Y.Tatsumi 和 S.Nohda：“日本东北弧原生岩浆成分的时间变化”岛弧。

日下部 実: "水素同位体比から見たマグマの脱水プロセス-雲仙1991年および富士山1707年噴火の例-" 地質学論集. 46. 105-113 (1996)

Minoru Kusakabe：“从氢同位素比率看出的岩浆脱水过程 - 云仙 1991 年和富士山 1707 年喷发的例子”地质评论 46. 105-113 (1996)。

M.Kusakabe: "Magma degassing in view of hydrogen and carbon isotopic ratios,and its consequences" Advances in Mass Spectrometry. 13(in press). (1995)

M.Kusakabe：“考虑到氢和碳同位素比率的岩浆脱气及其后果”质谱学进展。

S.Yamashita, Y.Tatsumi, and S.Nohda: "Temporal variation in primary magma compositions in the northeast Japan Arc." Island Arc. 5(印刷中). (1996)

S. Yamashita、Y. Tatsumi 和 S. Nohda：“日本东北部岛弧 5 中原生岩浆成分的时间变化”（1996 年）。

M.Kusakabe: "Magma degassing in view of hydrogen and carbon isotopic ratios,and its consequences" Advances in Mass Spectrometry. 13. 361-373 (1995)

M.Kusakabe：“考虑到氢和碳同位素比率的岩浆脱气及其后果”质谱学进展。