Influence of protons on Fe‐Mg interdiffusion in olivine
Influence of protons on Fe‐Mg interdiffusion in olivine
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DOI：
10.1029/2004jb003292
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发表时间：
2004-12
影响因子：
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通讯作者：
S. Hier‐Majumder;I. Anderson;D. Kohlstedt
中科院分区：
文献类型：
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作者：
S. Hier‐Majumder;I. Anderson;D. Kohlstedt
[1]本文报道了在压力为0.1 ~ 6 GPa、温度为1373 ~ 1450 K的水饱和环境中，橄榄石沿着[001]晶向铁镁互扩散系数的实验测量结果。橄榄石中水质子的浓度通过改变水逸度来控制。氧逸度由Ni-NiO固相反应决定，而二氧化硅的活性由斜方辉石的存在控制。在这项工作中，我们报告了扩散率作为温度、压力和水逸度的函数，遵循关系式Fe-Mg = exp [−（Q + PV*）/RT] m2 s −1，其中log（Do）=（−14.8 ± 2.7），r = 0.9 ± 0.3，Q = 220 ± 60 kJ/mol，V* =（16 ± 6）× 10− 6 m3/mol。随着水逸度的增加，扩散率的近似线性增加与八面体阳离子空位相关的质子的掺入形成缺陷复合物是一致的。结果表明，在压力为5GPa，温度为1373 K的条件下，阳离子在水饱和橄榄石中的扩散速度比在无水条件下快了50倍.
[1] We report the experimental measurement of Fe-Mg interdiffusivity in olivine along the [001] crystallographic direction in a water-saturated environment at pressures of 0.1 to 6 GPa and temperatures between 1373 and 1450 K. The concentration of water-derived protons in olivine was controlled by varying the water fugacity. The oxygen fugacity was set by the Ni-NiO solid state reaction, while the activity of silica was controlled by the presence of orthopyroxene. In this work, we report diffusivity as a function of temperature, pressure, and water fugacity following the relation Fe–Mg = exp [−(Q + PV*)/RT] m2s−1, where log(Do) = (−14.8 ± 2.7), r = 0.9 ± 0.3, Q = 220 ± 60 kJ/mol, and V* = (16 ± 6) × 10−6m3/mol. The approximately linear increase in diffusivity with increasing water fugacity is consistent with incorporation of protons associated with octahedral cation vacancies to form defect complexes. Our results indicate that cation diffusion in water-saturated olivine is ∼50 times faster than under water-absent conditions at a pressure of 5 GPa and a temperature of 1373 K.