Deformation-enhanced reaction in experimentally deformed plagioclase-olivine aggregates
Deformation-enhanced reaction in experimentally deformed plagioclase-olivine aggregates
复制标题
实验变形斜长石-橄榄石聚集体的变形增强反应
DOI：
10.1007/s00410-006-0171-7
复制
发表时间：
2007
影响因子：
3.5
通讯作者：
H. Stünitz
中科院分区：
文献类型：
--
作者：
A. D. Ronde;H. Stünitz
采用静态和剪切变形实验研究了变形对钙长石+橄榄石→cpx + opx +尖晶石±gt净传递反应动力学的影响。实验在干钙长石橄榄石（An92-Fo93）样品上进行，温度为900℃，压力为1000 ~ 1600 MPa。变形（“非流体静力”）和未变形（“静态”）样品在相岩石学、反应速率和反应机制方面进行了比较。从反应环结构看，钙长石+橄榄石反应是扩散控制的。在未变形的样品中，反应开始延迟和反应速率低表明在干燥条件下反应产物成核缓慢，扩散速度慢，即使在700 - 900mpa围压超标时也是如此。在变形的氧化铵样品中，反应速率提高。较高的成核速率主要是由于反应物和生成物的高应力和粘性变形过程共同作用，导致生成物的成核速率增加。结果表明，在没有流体渗透的情况下，粘性变形过程可以单独负责干燥岩石中变质反应的启动和局部化。
The effects of deformation on the kinetics of the net-transfer reaction anorthite + forsterite → cpx + opx + spinel ± gt were studied using static and shear deformation experiments. Experiments were performed on dry anorthite-olivine (An92–Fo93) samples at 900°C and pressures between 1,000 and 1,600 MPa in a Griggs apparatus. Deformed (‘non-hydrostatic’) and undeformed (‘static’) samples are compared in terms of phase petrology, reaction rate and reaction mechanisms. Anorthite + olivine reactions are diffusion-controlled as seen from reaction rim structures. In undeformed samples, delayed reaction onset and low reaction rates demonstrate sluggish nucleation of reaction products and slow rates of diffusion at dry conditions, even at 700–900 MPa confining pressure overstepping. The reaction rate is enhanced in deformed An–Fo samples. The higher rate is mainly attributed to a combination of high stresses and viscous deformation processes of the reactants and products, which cause an increase in the nucleation rate of products. The results imply that viscous deformation processes alone can be responsible for the initiation and localisation of metamorphic reactions in dry rocks in the absence of fluid infiltration.