Microtectonics, deformation mechanisms and rheology of surface reaching salt extrusions

盐冰川从岩盐（NaCl）的挤压山脉流下，在许多沉积盆地的演化中发挥了重要作用。这些特殊结构中的岩盐比深层地下的岩盐软得多，并且它通过溶解-沉淀蠕变变形到非常大的应变，所述溶解-沉淀蠕变由小粒度和晶界中的水的痕迹激活。本研究项目的主要目的是通过整合两个不同尺度的分析，量化伊朗和阿曼活动盐挤压体中岩盐的变形机制。在尺度的晶界（nm）的样品将通过一些不同的方法在高分辨率低温扫描电镜，它允许稳定的水膜在晶界在77 K，原位样品制备离子束挖掘和观察的冻结流体在高分辨率，结合微量化学分析与EDX的研究。我们将研究从积极变形岩盐的晶界，并探讨如何雨水渗透的盐质量通过实验室实验切割的CRYO-SEM。这将使我们能够测试在固溶-沉淀蠕变晶界结构的不同模型，这在过去的20年里一直备受争议。在颗粒（mm）尺度下，将通过透射光显微镜对伽马装饰（蓝色）薄切片进行研究，使用反射紧密显微镜对抛光和化学蚀刻样品进行亚晶粒尺寸古压差测量，并使用EBSD和氦渗透率测量进行取向成像。这项研究的结果将形成盐冰川变形机制的定量（数值）模型的基础。这些将用于盐构造的地质力学模型。该项目的第二个目的是利用活动变形的岩盐糜棱岩作为碳酸盐和硅酸盐岩石中活动剪切带的模型，这些岩石在中地壳约15公里深处变形，无法直接取样。我们将把我们的结果与中地壳剪切带的样品分析进行比较，以改进解释这些岩石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.