Project Details
Projekt
Microtectonics, deformation mechanisms and rheology of surface reaching salt extrusions
Applicant
Professor Dr. Janos L. Urai (†)
Subject Area
Palaeontology
Term
from 2006 to 2011
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 22241365
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.
DFG Programme
Research Grants
International Connection
France, Iran, Netherlands, United Kingdom
Major Instrumentation
Kryo-FIB-Workstation mit EDX, Kryo-Präparation, Beschichtungseinheit und Kryo-Shuttle (Sonderanfertigung)
Instrumentation Group
5120 Rasterelektronenmikroskope (REM)
