Element partitioning and diffusion in silicate high pressure phases

硅酸盐高压相中的元素分配和扩散

• 批准号: 08454151
• 负责人: KATO Takumi
• 金额: $ 4.8万
• 依托单位: UNIVERSITY OF TSUKUBA
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08454151/
• 关键词: High pressure and high temperature experiments; Materials in the Earth's interior; High pressure phase minerals; 地球内部物性; 地球内部; 高圧鉱物; 岩石物性; 地球化学

Chemical heterogeneity in the Earth's mantle is produced by the magmatic fractionation near the surface and is ultimately erased out by diffusion in minerals in the deep mantle conditions during subduction and convective circulation processes. Rheological properties of the mantle materials are also determined by the diffusion- controlled micro-mechanism. The major constituents of the lower mantle are orthorhombic silicate perovskite and magnesiowustite. Therefore, studies on diffusion of elements in these minerals provide important constraints on the processes in the lower mantle and, thereby, the whole mantle dynamics. However, properties of diffusion of these minerals are poorly known. We have made high pressure and high temperature experiments to observe reaction between MgSiO_3 perovskite and FeO wustite. Mode and extent of the reaction are used to estimate Mg-Fe inter-diffusion coefficients in ferromagnesian silicate perovskite and magnesiowustatite. High pressure and high temperature experiments have been made by an MA8 type high pressure apparatus driven by 3k ton. The most prominent process of the magmatic differentiation near the surface is the formation of the oceanic crust at the mid oceanic ridges. It returns back into the mantle at the subduction zones after some metamorphic and igneous differentiation. The fate of the subducted oceanic crust is an issue under considerable debate. However, it is conceivable that the chemical characteristics of the oceanic crust would be ultimately lost by the mechanical deformation (thinning) in the convective circulation and the diffusive dissolution. The bulk diffusion coefficients and element partitioning relations revealed in the present studies surely give important constraints on the geochemical evolution and mantle convection.

地球地幔中的化学不均匀性是由地表附近的岩浆分馏产生的，并最终通过俯冲和对流循环过程中深地幔条件下矿物的扩散而消除。地幔物质的流变特性也是由扩散控制的微观机制决定的。下地幔的主要成分是斜方晶系的硅酸盐钙钛矿和镁橄榄石。因此，对这些矿物中元素扩散的研究，对下地幔的过程乃至整个地幔动力学都有重要的制约作用。然而，这些矿物的扩散特性知之甚少。我们进行了高压和高温实验，观察了MgSiO_3钙钛矿与FeO方氏体之间的反应。利用反应方式和反应程度估算了镁钙钛矿和镁华铁矿中Mg-Fe互扩散系数。在一台3000吨驱动的MA 8型高压装置上进行了高温高压实验。近地表岩浆分异最显著的过程是洋中脊洋壳的形成。在俯冲带经过变质和火成分异作用后，又返回地幔。俯冲洋壳的命运是一个争论很大的问题。然而，可以想象的是，洋壳的化学特性最终会由于对流环流中的机械变形（减薄）和扩散溶解而丧失。研究揭示的体扩散系数和元素分配关系对地球化学演化和地幔对流具有重要的制约作用。

项目成果

M.Sasaki, M.Kurosawa et al.: "Characterization of a magnatic/meteoric transition Zone at the Kakkonda geothermal system, northeast Japan." Proc.9th Water-Rock Interaction. 483-486 (1998)

M.Sasaki、M.Kurosawa 等人：“日本东北部 Kakkonda 地热系统的磁/流星过渡带的特征。”

K.Takaknashi and T.Kato: "High pr essure melting of Mg2SiO4-(Mg,Ca)2Si2O6" Phys.Chem Minerals. (1997)

K.Takaknashi 和 T.Kato：“Mg2SiO4-(Mg,Ca)2Si2O6 的高压熔化”物理化学矿物。

T.KATO, ET.AL.: "MELTING EXPERIMENTS ON FORSTERiTE-PYROPE SYSTEM AT 8 AND 13.5 GPa" PHySiCS OF THE EARTH AND PLANETARY INTERiORS. 107. 97-102 (1998)

T.KATO, et.al.：“镁橄榄石-镁铝榴石系统在 8 和 13.5 GPa 下的熔化实验”地球和行星内部物理学。

M.Kurosawa et al.: "Design of a new sample chamber for proton microprobe analysis of mineral samples." Nuclear Instr.Meth.Phys.Res.B142. 599-605 (1998)

M.Kurosawa 等人：“设计用于矿物样品质子微探针分析的新型样品室。”

T.KATO ET.AL.: "Melting experiments on the forsterite-pyrope system at 8 and 13.5 GPa" Physics of the Earth and Planetary Interiors,. 107. 97-102 (1998)

T.KATO 等人：“镁橄榄石-镁铝榴石系统在 8 和 13.5 GPa 下的熔化实验”，《地球和行星内部物理学》。