A dehydroxylation kinetics study of brucite Mg(OH)(2) at elevated pressure and temperature
A dehydroxylation kinetics study of brucite Mg(OH)(2) at elevated pressure and temperature
复制标题
水镁石Mg(OH)(2)在高温高压下的脱羟基动力学研究
DOI：
10.1007/s00269-016-0857-y
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发表时间：
2017
影响因子：
1.4
通讯作者：
Liu Tao
中科院分区：
文献类型：
--
作者：
Liu Chuanjiang;Wang Duojun;Zheng Haifei;Liu Tao
我们使用热液金刚石砧池在 593–633 K 和 668–1655 MPa 的压力和温度范围内，对水饱和条件下的水镁石进行了原位脱羟基动力学研究。使用涉及成核和生长过程的 Avrami 型模型对等温-等压数据进行动力学分析，得出脱羟基速率和反应级数的值，该值与受结构 OH 基团水分子单维扩散限制的反应机制兼容。我们的结果显示负压力对反应速率的依赖性和正温度对 k 的依赖性。水镁石脱羟基产生的活化体积 ΔV 值为 5.03 cm3/mol。根据阿伦尼乌斯关系，在实验 P-T 范围内，该过程的表观活化能 Ea 计算为 146 kJ/mol。据确定，从 4.4 × 10−7 到 10.7 × 10−7 范围内的流体产生速率比地幔蛇纹岩的应变速率大几个数量级，其速度可能快到足以导致岩石的脆性破裂。此外，当水镁石出现在俯冲带的无/低H2O环境中时，产液速率将会提高。
We performed an in situ dehydroxylation kinetics study of brucite under water-saturated conditions in the pressure and temperature ranges of 593–633 K and 668–1655 MPa using a hydrothermal diamond anvil cell. The kinetic analysis of the isothermal–isobaric data using an Avrami-type model involving nucleation and growth processes yields values for the dehydroxylation rate and reaction order compatible with a reaction mechanism limited by the monodimensional diffusion of water molecules from structural OH groups. Our results show a negative pressure dependence on the reaction ratekand a positive temperature dependence on thek. The dehydroxylation of brucite yields an activation volume ∆Vvalue of 5.03 cm3/mol. Following the Arrhenius relationship, the apparent activation energyEaof the process is calculated to be 146 kJ/mol within the experimentalP–Tranges. It is determined that the fluid production rates varying from 4.4 × 10−7to 10.7 × 10−7are a few orders of magnitude greater than the strain rate of the mantle serpentinites, which may be fast enough to result in the brittle fracture of rocks. Moreover, the rate of fluid production will be enhanced when brucite occurs in the non-/low H2O environments of the subduction zone.