Microtectonics, deformation mechanisms and rheology of surface reaching salt extrusions

从岩盐 (NaCl) 挤压山流下的盐冰川在许多沉积盆地的演化中发挥了重要作用。这些特殊结构中的石盐比深层地下的石盐软得多，并且通过由小晶粒尺寸和晶界中的微量水激活的溶液沉淀蠕变而变形至非常大的应变。该研究项目的中心目标是通过整合两个不同尺度的分析来量化伊朗和阿曼活性盐挤压中石盐的变形机制。在晶界 (nm) 尺度上，我们将通过高分辨率低温 SEM 中的多种不同方法来研究晶界 (nm) 样品，从而使晶界中的水膜在 77 K 下稳定，通过离子束挖掘进行原位样品制备，以高分辨率观察冷冻流体，并结合 EDX 微化学分析。我们将研究岩盐主动变形的晶界，并通过冷冻扫描电镜 (CRYO-SEM) 进行的实验室实验研究雨水如何渗透盐团。这将使我们能够测试溶液沉淀蠕变中晶界结构的不同模型，这在过去二十年中一直是备受争议的话题。在颗粒 (mm) 尺度上，将通过伽马装饰（蓝色）薄片的透射光显微镜、使用反射紧密显微镜的抛光和化学蚀刻样品的亚晶粒尺寸古深度测量以及使用 EBSD 和氦渗透率测量的定向成像来研究样品。这项研究的结果将构成盐冰川变形机制定量（数值）模型的基础。这些将用于盐构造的地质力学模型。该项目的第二个目标是利用活跃变形的石盐糜棱岩作为碳酸盐岩和硅酸盐岩石中活跃剪切带的模型，这些岩石在大约 15 公里深度的中地壳中变形，无法直接采样。我们将把我们的结果与挖出的中地壳剪切带样本的分析进行比较，以改进解释这些岩石的变形机制和流变学的微构造工具箱。

Salt glaciers which flow downhill from extruded mountains of Halite (NaCl) have played a major role in the evolution of many sedimentary basins. Halite in these extraordinary structures is much softer than Halite in the deep subsurface, and it deforms to very large strains by solutionprecipitation creep activated by the small grainsize and traces of water in the grain boundaries. The central aim of this research project is to quantify the deformation mechanisms of Halite in active salt extrusions in Iran, and Oman, by integrating analyses at two different scales. At the scale of the grain boundaries (nm) samples will be studied by a number of different methods in a high resolution cryogenic SEM, which allows stabilization of the water films in the grain boundaries at 77 K, in situ sample preparation by ion-beam-excavation and observation of the frozen fluid at high resolution, combined with microchemical analysis with EDX. We will study grain boundaries from actively deforming halite, and also investigate how rainwater penetrates the salt mass by laboratory experiments Mowed by CRYO-SEM. This will allow us to test the different models for grain boundary structure in solution-precipitation creep, which have been subject of much controversy for the past twenty years. At the scale of grains (mm) samples will be studied by transmitted light microscopy of gammadecorated (blue) thin sections, subgrain size paleopiezometry of polished and chemically etched samples using reflected tight microscopy and orientation imaging using EBSD and Helium permeability measurements. The results derived from this study will form the basis for a quantitative (numerical) model of deformation mechanisms in salt glaciers. These will be used in geomechanical models of salt tectonics. A secondary aim of the project is to use the actively deforming halite mylonites as a model for active shear zones in carbonate and silicate rocks which are deforming in the middle crust at around 15 km depth, inaccessible for direct sampling. We will compare our results with analyses of samples from exhumed middle crustal shear zones, to improve the microtectonics toolbox for interpretation of deformation mechanisms and rheology of these rocks.