Noble gas diffusivity hindered by low energy sites in amphibole
Noble gas diffusivity hindered by low energy sites in amphibole
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DOI：
10.1016/j.gca.2015.09.024
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发表时间：
2016-01-01
影响因子：
5
通讯作者：
Smye, Andrew J.
中科院分区：
文献类型：
--
作者：
Jackson, Colin R. M.;Shuster, David L.;Smye, Andrew J.
用高能质子辐照样品的逐步脱气分析，实验测定了He和Ne在四个角闪石样品中的扩散动力学，并用Arrhenius关系式进行了拟合。初步的发现是，在具有较高密度的空环位置的角闪石中，He和Ne的扩散系数系统地较低，这表明未被占据的环位起到了迁移惰性气体的陷阱的作用。角闪石中惰性气体扩散系数的环位影响对应用于这些相的40Ar/39Ar热年代学和俯冲带惰性气体再循环的效率具有重要意义。这些发现与闪石中惰性气体溶解度与空置环位浓度之间的相关性(Jackson等人，2013a，2015)一致，但与惰性气体扩散的离子孔隙度模型(Fortier和Giletti，1989；Dahl，1996)不一致。相反，这些发现表明，离子孔隙度的拓扑结构和离子孔隙率的绝对体积在决定稀有气体的扩散速度方面存在竞争。(C)2015爱思唯尔有限公司。保留所有权利。
The diffusion kinetics of He and Ne in four amphibole specimens have been experimentally determined using stepwise degassing analysis of samples previously irradiated with energetic protons, and Arrhenius relationships have been fit to these data. The primary finding is that He and Ne diffusivities are systematically lower in amphiboles that have higher concentrations of unoccupied ring sites, suggesting that unoccupied ring sites act as traps for migrating noble gases. Ring site influence of noble gas diffusivity in amphiboles has substantial implications for 40Ar/39Ar thermochronology applied to these phases and the efficiency of noble gas recycling in subduction zones. These findings are consistent with the correlation between noble gas solubility and the concentration of unoccupied ring sites in amphibole (Jackson et al., 2013a, 2015) but are inconsistent with the ionic porosity model for noble gas diffusion (Fortier and Giletti, 1989; Dahl, 1996). Rather, these findings suggest that the topology of ionic porosity and absolute volume of ionic porosity compete in determining the rate at which noble gases diffuse. (C) 2015 Elsevier Ltd. All rights reserved.