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Aluminum diffusion in zircon
Chemical Geology ( IF 3.6 ) Pub Date : 2021-09-03 , DOI: 10.1016/j.chemgeo.2021.120510
D.J. Cherniak 1
Affiliation  

Al diffusion under anhydrous 1-atm conditions has been measured in natural zircon. Experiments used a source consisting of AlPO4-ZrSiO4 powder mixtures. Experiments were run in air in crimped Pt capsules. Al profiles were measured with Nuclear Reaction Analysis (NRA) using the reaction 27Al(p, γ)28Si. For diffusion parallel to c, the following Arrhenius relation is determined:

D = 6.24 × 103 exp.(−774 ± 34 kJ mol−1 /RT) m2s−1

Diffusivities normal and parallel to c are similar, indicating little anisotropy of diffusion of Al.

Al diffuses more rapidly than tetravalent cations that substitute on the Si site in zircon, but more slowly than trivalent cations substituting on the Zr site. These slow diffusivities indicate that Al chemical signatures will be quite resistant to diffusional alteration. For example, Al compositions at the center of 50 μm radius zircon grains would be preserved over times greater than the age of the earth at temperatures in excess of 1000 °C.



中文翻译:

锆石中的铝扩散

已在天然锆石中测量了无水 1-atm 条件下的 Al 扩散。实验使用由AlPO 4 -ZrSiO 4粉末混合物组成的源。实验在空气中在卷曲的 Pt 胶囊中进行。使用反应27 Al(p, γ) 28 Si通过核反应分析 (NRA) 测量 Al 分布。对于平行于 c 的扩散,确定以下 Arrhenius 关系:

D = 6.24 × 10 3 exp.(−774 ± 34 kJ mol -1 /RT) m 2 s -1

与 c 垂直和平行的扩散率相似,表明 Al 扩散的各向异性很小。

Al 的扩散比取代锆石 Si 位的四价阳离子更快,但比取代 Zr 位的三价阳离子更慢。这些缓慢的扩散表明铝化学特征对扩散改变具有很强的抵抗力。例如,在超过 1000 °C 的温度下,半径为 50 μm 的锆石晶粒中心的 Al 成分将被保存超过地球年龄的时间。

更新日期:2021-09-16
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