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Determination of interdiffusivity in major rock-forming minerals

主要造岩矿物相互扩散率的测定

基本信息

批准号：
11440161
负责人：
OZAWA Kazuhito
金额：
$ 8.77万
依托单位：
The University of Tokyo (2000-2001)Okayama University (1999)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11440161/
关键词：
diffusion chromite olivene spinel evoporation

项目摘要

In this research project, cation diffusion in olivine and Cr-Al spinel was examined by vacuum evaporation technique. The Fe-Mg interfiffusion and Ni tracer diffusion coefficients in olivine were determined at 1300〜1500℃ with gem-quality San Carlos olivine. The composition dependence and anisotropy were determined by applying a diffusion model with moving boundary. The diffusivity was found to be largest along the c-axis, intermediate along the b-axis, and smallest along the a-axis. At 1400℃, the interfifusion coefficient is estimated to be 8.7x10^<-15>±2.8(m^2/sec) along the c-axis. The anisotropy was also significant at 1500 and 1300℃, but there is a tendency that the diffusivities along a-and b-axis become similar at lower temperatures. Elemental diffusion in Cr-Al spinel was studied on octahedral chromian spinel from the Horokanai ophiolite at 1300〜1500℃. The spinel samples were evaporated incongruently developing outer reaction zone with low iron content and inner diffusion zone. By analyzing the compositional profile, the magnetite component was selectively evaporated through rapid diffusion promoted by point defects derived from reduction of ferric iron to ferrous iron. At 1300 and 1400℃, Al shows marked uphill diffusion, which clearly indicate that the Cr diffusivity is much slower than that of Al.

本研究利用真空蒸镀技术研究了阳离子在橄榄石和铬铝尖晶石中的扩散。采用宝石级圣卡洛斯橄榄石，在1300〜1500℃下测定了橄榄石中铁镁互渗和镍示踪剂扩散系数。通过应用具有移动边界的扩散模型来确定组分依赖性和各向异性。发现扩散率沿c轴沿着最大，沿b轴沿着居中，沿a轴沿着最小。在1400℃时，沿c轴的融合系数估计为8.7 × 10 ^<-15>±2.8（m^2/sec）沿着。各向异性在1500和1300℃也很明显，但在较低温度下，沿沿着a轴和b轴的扩散系数有变得相似的趋势。在1300 ~ 1500℃温度下，对来自幌冈内蛇绿岩的八面体铬尖晶石中的元素扩散进行了研究。尖晶石样品不均匀蒸发，形成低铁含量的外反应区和内扩散区。通过分析成分分布，磁铁矿组分通过由三价铁还原成二价铁的点缺陷促进的快速扩散而选择性地蒸发。在1300和1400℃时，Al的扩散呈明显的上坡扩散，这表明Cr的扩散速度比Al慢得多。