کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8910319 | 1637491 | 2018 | 12 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Chlorine diffusion in rhyolite under low-H2O conditions
دانلود مقاله + سفارش ترجمه
دانلود مقاله ISI انگلیسی
رایگان برای ایرانیان
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
The chlorine diffusivity in rhyolitic melts containing <1.2â¯wt% H2O was determined at 650â¯Â°C-950â¯Â°C and 1.5-11.8â¯MPa. Diffusion experiments were carried out by reacting rhyolitic obsidian with four types of chlorine sources including a pure Cl2 fluid, Cl2â¯+â¯H2O fluid mixture, molten NaCl, and NaCl aqueous solution. In the pure Cl2 experiments, the chlorine diffusivity ranged from 7.7â¯Ãâ¯10â18â¯m2/s (650â¯Â°C) to 8.2â¯Ãâ¯10â16â¯m2/s (950â¯Â°C); it is much lower than previously reported values for rhyolitic melt. The Cl2â¯+â¯H2O fluid mixture experiments revealed that the chlorine diffusivity strongly depends on the water content: it increased by 1-2 orders as the water content of the melt increased to ~1â¯wt%. In the molten NaCl experiments, sodium infiltrated into the melt while potassium diffused out. The chlorine diffusivity was higher than that in the pure Cl2 experiments by a factor of 4-10. A single experiment using NaCl solution as a chlorine source resulted in the highest Cl diffusivity, probably due to the high H2O and sodium contents. The activation energy of chlorine diffusion was 135-202â¯kJ/mol, and it is comparable to the activation energy in more mafic melts. Because the diffusivity of chlorine is much smaller than that of H2O and CO2, a strong diffusive fractionation is expected to occur during magma vesiculation and degassing. Calcium diffusion was observed as a by-product of chlorine diffusion under anhydrous conditions. In the pure Cl2 experiments, calcium diffusivity ranged from 6.2â¯Ãâ¯10â17â¯m2/s (650â¯Â°C) to 3.9â¯Ãâ¯10â14â¯m2/s (950â¯Â°C), and the activation energy was 177â¯Â±â¯15â¯kJ/mol. In molten NaCl experiments, the calcium diffusivity was higher by one order of magnitude, and the activation energy was similar to that for the pure Cl2 experiments.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemical Geology - Volume 483, 20 April 2018, Pages 619-630
Journal: Chemical Geology - Volume 483, 20 April 2018, Pages 619-630
نویسندگان
Shumpei Yoshimura,