Lattice diffusion coefficients and partition coefficients have been determined for Li, Mg, Al, Sc, Ti, Cr, V, Mn, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Lu, Hf, Ta and U in single crystals of natural magnetite as a function of oxygen fugacity ( f O 2 ) at 1150 °C and 1 bar by equilibration with a synthetic silicate melt reservoir. Most experiments were run for twelve hours, which was sufficient to generate diffusion profiles from 25 to > 1000 µm in length. The results were checked at one condition with two additional experiments at 66.9 and 161 h. The profiles were analysed using scanning laser-ablation inductively-coupled-plasma mass-spectrometry. Diffusion coefficients ( D ) were calculated by fitting data from individual element diffusion profiles to the conventional diffusion equation for one-dimensional diffusion into a semi−infinite slab with constant composition maintained in the melt at the interface. Equilibrium magnetite/melt partition coefficients are given by the ratio of the interface concentrations to those in the melt. Plots of log D as a function of log f O 2 produce V-shaped trends for all the investigated elements, representing two different mechanisms of diffusion that depend on ( f O 2 ) −2/3 and ( f O 2 ) 2/3 . Diffusion coefficients at a given f O 2 generally increase in the order: Cr < Mo ≈ Ta < V < Ti < Al < Hf ≈ Nb < Sc ≈ Zr ≈ Ga < In < Lu ≈ Y < Ni < U ≈ Zn < Mn ≈ Mg < Co < Li < Cu. Thus, Cu contents of magnetites are most susceptible to diffusive reequilibration, whereas the original content of Cr should be best preserved.

中文翻译：

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磁铁矿中微量元素和微量元素的扩散和分配系数与 1150 ºC 下氧逸度的函数关系

已确定 Li、Mg、Al、Sc、Ti、Cr、V、Mn、Co、Ni、Cu、Zn、Ga、Y、Zr、Nb、Mo、In、Lu、Hf、天然磁铁矿单晶中的 Ta 和 U 作为氧逸度 (f O 2 ) 的函数，在 1150 °C 和 1 bar 下通过与合成硅酸盐熔体储层平衡。大多数实验进行了 12 小时，这足以生成长度从 25 到 > 1000 µm 的扩散曲线。在 66.9 和 161 小时的两个额外实验中，在一种条件下检查结果。使用扫描激光烧蚀电感耦合等离子体质谱法分析轮廓。扩散系数 (D) 是通过将来自单个元素扩散曲线的数据拟合到常规扩散方程来计算的，用于一维扩散到半无限板中，在界面处保持恒定的成分。平衡磁铁矿/熔体分配系数由界面浓度与熔体中的浓度之比给出。log D 作为 log f O 2 的函数的图为所有研究的元素产生 V 形趋势，代表取决于 ( f O 2 ) -2/3 和 ( f O 2 ) 2/3 的两种不同的扩散机制. 给定 f O 2 下的扩散系数通常按以下顺序增加： Cr < Mo ≈ Ta < V < Ti < Al < Hf ≈ Nb < Sc ≈ Zr ≈ Ga < In < Lu ≈ Y < Ni < U ≈ Zn < Mn ≈ Mg < Co < Li < Cu。因此，