The effect of stress/strain-induced texture evolution and grain boundary mobility on reaction rim growth in the wet system MgO-SiO2

在高温下矿物反应过程中，构造力或体积变化所产生的非等静应力会引起岩石的非弹性蠕变，并可能与反应过程相互作用。同时，变质反应可显著改变体流变行为。我们建议在受控的实验室条件下通过结构缺陷来研究矿物反应和塑性变形之间的相互作用。建议的体系CaCO3 - MgCO3允许研究a)方解石和菱镁矿单晶中白云石的生长和b)镁在方解石中与白云石接触的方解石中的溶解。试验将在高达900°C的温度和400 MPa的围压下进行，使用帕特森型变形仪在三轴和扭转条件下施加轴向和剪切应力。据推测，白云石边缘的生长速率以及镁方解石的形成速率取决于诱导结晶缺陷的差应力。这些包括点缺陷，例如空位或间隙，线缺陷（位错）和平面缺陷，例如高角度晶界或孪晶界。主要的缺陷预算和相关的织构和晶界特征分布取决于施加的应力和应变，可以用现代电子显微镜分析。此外，正在进行的反应可能会通过溶质阻力、沉淀硬化、点缺陷浓度增加或主要变形机制的切换来改变骨料的强度。从力学数据和微观结构分析可以推断出流变行为。该项目在一定程度上是前项目6（“在运输控制的矿物反应和差异应力之间的反馈”）的延续和扩展，该项目在第一申请阶段进行了审查。在前人研究的基础上，我们着重定量研究了应力-应变结构缺陷对矿物反应动力学和强度演化的影响。

Non-isostatic stresses created by tectonic forces or volume changes during mineral reactions at high temperature induce inelastic creep of rocks that may interact with the reaction progress. Simultaneously, metamorphic reactions may considerably alter the bulk rheological behaviour. We propose to investigate the interplay between mineral reaction and plastic deformation via structural defects at controlled laboratory conditions. The suggested system CaCO3 – MgCO3 allows to study a) the growth of dolomite from calcite and magnesite single crystals and b) the dissolution of Mg in calcite from calcite in contact with dolomite. Tests will be performed at temperatures up to about 900°C and confining pressures of 400 MPa by applying axial and shear stresses under triaxial and torsion conditions using a Paterson-type deformation apparatus. Presumably, the dolomite rim growth rates as well as the formation rates of magnesian calcite depend on differential stress through induced crystalline defects. These comprise point defects, e.g. vacancies or interstitials, line defects (dislocations), and planar defects as for example high angle grain boundaries or twin boundaries. The predominant defect budget and associated texture and grain boundary character distribution depend on the applied stress and strain, which can be analyzed using modern electron microscopy. In addition, ongoing reactions may change the aggregate strength via solute drag, precipitation hardening, increased point defect concentration, or by a switch in the prevailing deformation mechanism. The rheological behaviour can be deduced from mechanical data combined with microstructure analysis. The project is partly a continuation and extension of the former project 6 (‘feedback between transport controlled mineral reactions und differential stress’) examined during the first application phase. Based on the previous findings we focus on a quantitative examination of the effect of stress-strain induced structural defects on the kinetics of mineral reactions and on the strength evolution.