Effect of pressure on the viscosity of molten iron : experimental study on the viscosity of the outer core

压力对铁水粘度的影响：外芯粘度的实验研究

• 批准号: 08640524
• 负责人: YASUDA Atsushi
• 金额: $ 1.54万
• 依托单位: University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08640524/
• 关键词: viscosity; molten metal; diffusivity; silicate melt; melt structure; viscosity; molten metal; diffusivity; silicate melt; melt structure

The viscosity of the earth's outer core is one of the most important physical property of the earth because it has significant influence on the thermal and material transport in the deep earth. In spite of its importance, it is probably the least well-known property of the earth. The purpose of the present study is to give a constraint on the viscosity of outer core from high pressure experiments. Effect of pressure on the physical property and structure of melt was studied.Water diffusivities in basaltic and rhyolitic melts were determined at 2 and 3 GPa and 1450ﾟC.Contrary to previous studies at low pressures, water diffusivity is not sensitive to the water content at 3 GPa, and the measured total water concentration profiles can be practically fitted by a single constant diffusion coefficient for total water. Water diffusivities are 4.7_x10^<-10>m^2/s in the basaltic melt (0.14-2.3 wt% water) and 1.8_x10^<-10>m^2/s in the rhyolitic melt (1.5-3.1 wt% water) at 3 GPa and 1450ﾟC.On the other hand, water diffusivity at 2 GPa and 1450ﾟC in the basaltic melt depends on the water-concentration ; 1.4_x10^<-10>m^2/s at 0.4 wt% water and 5.6_x10^<-10>m^2/s at 1.6 wt% water. However, this dependence is smaller than that expected from previous studies at lower pressures. Present experimental results suggest that the diffusivity of OH species increases with increasing pressure whereas that of molecular H_2O decreases, and consequently the former becomes comparable to the latter at about 3 GPa.Diffusion of Ni in molten Au was measured up to 3 GPa and it is 2.3+-0.4_x10^<-9>m^2/s at 1 GPa and 1200ﾟC,and 2.3-3.7_x10^<-9>m^2/s at 3 GPa snd 1300ﾟCApplying Sutherland-Einstein equation to the measured diffusivity, viscosity of Au at high pressure was calculated. The resultant viscosity is consistent with viscosities using theoretical estimation such as Andrade's formula.

地球外部芯的粘度是地球最重要的物理特性之一，因为它对地球中的热和材料传输具有重大影响。尽管它很重要，但它可能是地球上最不著名的财产。本研究的目的是从高压实验中对外芯的粘度产生限制。压力对熔体的物理特性和结构的影响是研究的。在2和3 GPA和3 GPA和1450 ﾟC. C.对抗性下，在低压下，水的水分在3 GPA上不敏感，在3 GPA的水中不敏感，在3 GPA的水中不敏感，并且总的水浓度分配在单个不变的水分中，对水的难度不敏感。水的难度为4.7_x10^<-10> m^2/s（0.14-2.3 wt％水）和1.8_x10^<-10> m^2/s，在3 gpa和1450 c.on c.on c.on c.on c.on和1450 gpa的含量（1.5-3.1 wt％水）中（1.5-3.1 wt％水）（1.5-3.1 wt％的水）c.水分； 1.4_x10^<-10> m^2/s在0.4 wt％水和5.6_x10^<-10> m^2/s时1.6 wt％水。但是，这种依赖性比以前在较低压力下的研究所期望的依赖性小。目前的实验结果表明，OH物种的难度随着压力增加而增加，而分子H_2O的压力降低，因此前者与后期大约3 GPA相比。熔融Au中Ni的扩散最多为3 GPA，并且是2.3+-0.4_x10^+-0.4_x10^<-9> M^2/s at 1 gpa和1200 gpa and and 1200 r. 2.3-3.7_x10^<-9> 9> m^2/s在3 GPA SND 1300 ﾟ capplying Sutherland-Einstein方程式达到测得的难度，计算高压下AU的粘度。最终的粘度与使用理论估计（例如安德拉德公式）的粘度一致。