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Microtectonics, deformation mechanisms and rheology of surface reaching salt extrusions

到达地表盐挤压的微观构造、变形机制和流变学

基本信息

批准号：
22241365
负责人：
Professor Dr. Janos L. Urai (†)
金额：
--
依托单位：
Department of Earth and Ocean Sciences
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2006
资助国家：
德国
起止时间：
2005-12-31 至 2010-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/22241365?language=en
关键词：
Microtectonics deformation mechanisms rheology surface

项目摘要

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.

盐冰川是由盐岩山挤压而成的，在许多沉积盆地的演化中起着重要作用。这些特殊结构中的岩盐比地下深处的岩盐要软得多，并且由于细小的晶粒和晶界中微量的水而激活的溶蚀-沉淀蠕变，使其变形成非常大的应变。本研究项目的中心目标是通过整合两种不同尺度的分析，量化伊朗和阿曼活性盐挤压中岩盐的变形机制。在晶界（nm）尺度上，样品将通过多种不同的方法在高分辨率低温扫描电镜下进行研究，这使得晶界中的水膜在77 K时稳定，通过离子束挖掘和高分辨率冷冻流体观察来原位制备样品，并结合EDX的微化学分析。我们将从主动变形的岩盐中研究晶界，并通过CRYO-SEM进行室内实验，研究雨水如何穿透盐块。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争议的主题。在颗粒（毫米）尺度上，将通过透射光学显微镜对伽玛修饰（蓝色）薄片进行研究，使用反射紧密显微镜对抛光和化学蚀刻样品进行亚颗粒大小古厚度测量，使用EBSD和氦渗透率测量进行定向成像。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使用活跃变形的岩盐糜棱岩作为碳酸盐岩和硅酸盐岩石中活动剪切带的模型，这些剪切带在大约15公里深的中部地壳中变形，无法直接采样。我们将把我们的结果与中地壳剪切带样品的分析结果进行比较，以改进微构造工具箱，以解释这些岩石的变形机制和流变学。