Abstract Bromine diffusion was measured in two natural phonolitic melts: (1) a K2O-rich (~10 wt%) one synthesized from the white pumice phase of the 79 AD eruption of Vesuvius (Italy), and (2) a Na2O-rich (~10 wt%) one corresponding to the most differentiated melt of the 12 000 BC eruption of the Laacher See (Germany). Experiments were performed at 0.5 and 1.0 GPa, 1250 to 1450 °C, at anhydrous and hydrous (2.65 ± 0.35 wt% of dissolved water) conditions. Experiments conducted with the diffusion-couple technique in the piston cylinder were performed with only bromine diffusing and with the simultaneous diffusion of a halogen mixture (F, Cl, Br) to evaluate the interactions between the halogens during diffusion. The diffusion profiles of Br were measured by X-ray fluorescence using synchrotron radiation microprobe (SYXRF), ID18F, at the European Synchrotron Radiation Facility (ESRF, France). Bromine diffusion displays Arrhenian behavior under anhydrous conditions that is similar when it diffuses alone and when it diffuses with F and Cl. The Br diffusion coefficients range between 2 × 10–12 m2/s at 1250 °C and 1.5 × 10–11 m2/s at 1450 °C for the Na-rich melt and between 3 × 10–12 m2/s at 1250 °C and 2.5 × 10–11 m2/s at 1450 °C for the K-rich melt, at 1.0 GPa. Although Br mobility is independent of F and Cl in anhydrous phonolitic melts, its behavior may be dependent on the dominant alkali in the melt, as previously observed for Cl, but not F. For hydrous experiments, although the data are scattered, the Br diffusivity increases slightly with water and the Na/K ratio seems to influence Br diffusivity. Similarly to noble gases, halogen diffusivity at a given temperature in the phonolitic melts appears related to the ionic porosity of the silicate structure. Compared to basaltic melt, Br diffusivities are approximately one order of magnitude lower in the Na-phonolite melt, because of the difference of the pre-exponential factor. Br mobility appears to be decoupled from melt viscosity, considering the results here.

中文翻译：

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音素熔体中的溴扩散。与氟和氯扩散的比较

摘要 在两种天然音质熔体中测量了溴扩散：(1) 富含 K2O (~10 wt%) 的一种，由维苏威火山 (意大利) 公元 79 年喷发的白色浮石相合成，以及 (2) 富含 Na2O (~10 wt%) 一种对应于公元前 12 000 年 Laacher See（德国）喷发的差异最大的熔体。实验在 0.5 和 1.0 GPa、1250 至 1450 °C、无水和含水（溶解水的 2.65 ± 0.35 wt%）条件下进行。在活塞气缸中使用扩散耦合技术进行的实验仅在溴扩散和卤素混合物（F、Cl、Br）的同时扩散的情况下进行，以评估扩散过程中卤素之间的相互作用。使用同步辐射微探针（SYXRF），ID18F，通过X射线荧光测量Br的扩散曲线。在欧洲同步辐射设施（ESRF，法国）。溴扩散在无水条件下表现出类似的 Arrhenian 行为，当它单独扩散时和当它与 F 和 Cl 一起扩散时是相似的。富钠熔体的 Br 扩散系数在 1250 °C 时为 2 × 10-12 m2/s 和 1450 °C 时为 1.5 × 10-11 m2/s，1250 °C 时为 3 × 10-12 m2/s C 和 2.5 × 10–11 m2/s 在 1450 °C 下富钾熔体，1.0 GPa。尽管在无水音质熔体中 Br 的迁移率与 F 和 Cl 无关，但其行为可能取决于熔体中的主要碱，如先前对 Cl 所观察到的，而不是 F。 对于含水实验，尽管数据是分散的，但 Br 扩散系数随水略微增加，Na/K 比似乎影响 Br 扩散率。与惰性气体类似，在给定温度下，音素熔体中的卤素扩散率似乎与硅酸盐结构的离子孔隙率有关。与玄武岩熔体相比，由于指前因子的差异，钠-音沸石熔体中的 Br 扩散率大约低一个数量级。考虑到这里的结果，溴迁移率似乎与熔体粘度无关。