Dislocation recovery experiment of hydrous olivine as a function of water content and crystallographic orientation

形变实验表明，掺水可以提高位错的迁移率，[100](010)(A型)、[100](001)(E型)和[001](100)(C型)滑移的位错迁移率与水分的依赖程度依次较高。位错迁移率的总含水率指数应为1.2。为了检验这些结果，申请人在前一个项目中进行了位错恢复实验，并获得了以下结果。(1)尽管报道了至少四种组构类型(类型A、B、C和E)，但只有两种位错。A型和E型位错是具有[100]Burgers矢量的刃型位错(a-位错)，而B型和C型织构是具有[001]Burgers矢量的螺旋位错(c-位错)。(2)a-和c-位错的湮没速率常数的激活能和体积是相同的，并且与Si扩散的激活能和体积相当。这些事实表明，这两种位错的运动是扩散控制的。(3)a-位错和c-位错的湮没速率常数的含水量指数分别为0.2±0.4和-0.5±0.2。(1)[100](010)滑移的a-位错的湮没速率常数的不确定性很大。(2)[001](010)滑移的c-位错的湮没速率常数的数据点太少。(3)在任何情况下都不清楚是否真的没有位错。(4)不清楚引起B型和C型组构的c-位错是否相同。为此，本项目将进行以下实验：(1)将用更精确的技术重新研究a-位错湮没速率常数随水分含量变化的数据点。(2)将产生更多关于c-位错湮没速率常数随水分含量变化的数据点。(3)橄榄石单晶将在不同的压力、温度、温度和温度下沿(001)面沿[100]方向剪切。(4)[001](100)滑移c-位错的压力和温度依赖关系以及[001](010)滑移c-位错的水分依赖关系。

Deformation experiments suggested that dislocation mobility should be enhanced by water incorporation, and the water-content dependence of dislocation mobility in the [100](010) (Type-A), [100](001) (Type-E) and [001](100) (Type-C)slips should be higher in this order. The overall water-content exponent of dislocation mobility should be 1.2. In order to examine these results, the applicant conducted dislocation recovery experiment in the preceding project and obtained the following results. (1) In spite of at least four reported fabric types (Type A, B, C and E), there are only two kinds of dislocations. Dislocations for Type A and E fabrics are edge dislocations with a [100] Burgers vector (a-dislocations), whereas those for Type B and C fabrics are screw dislocations with a [001] Burgers vector (c-dislocations).(2) The activation energies and volumes of annihilation-rate constants of a- and c-dislocations are identical, and are also comparable with those of the Si diffusions. These facts suggest that motions of these two dislocations are diffusion-controlled. (3) The water-content exponents of annihilation-rate constants of a- and c-dislocations are 0.2±0.4 and -0.5±0.2, respectively. Namely, their water content dependences are zero with in uncertainty and negative, respectively.Although these striking results were thus obtained, there are insufficient Points.(1) Uncertainties of the annihilation-rate constants of a-dislocations by the [100](010) slip are very large.(2) Data points of the annihilation-rate constants of c-dislocations by the [001](010) slip are too few.(3) It is not clear whether dislocations accounting for Type-E fabric are really absent under any condition.(4) It is not clear whether c-dislocations responsible for Type-B and Type-C fabrics are identical or not. For these reasons, the following experiments will be conducted in this project.(1) Data points of water-content dependence of annihilation-rate constants of a-dislocations will be reinvestigated by means of more precise techniques.(2) More data points will be produced for water-content dependence of annihilation-rate constants of c-dislocations.(3) Olivine single crystals will be sheared in the [100] direction on the (001) plane under various pressure, temperature, strain-rate and water-content conditions to examine their dislocation textures.(4) Pressure and temperature dependence of c-dislocations by the [001](100) slip and water-content dependence of those by the [001](010) slip will be obtained.