Institute of Geophysics of the CAS, v. v. i.

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Folded fine-grained salt in Neuhof salt mine

Extremely deformed salt layer of fine-grained Upper Werra rock salt (0.3-2 m thick layer) within the Zechstein (Z1) sequence (Neuhof-Ellers mine) represents an instructive case of the initiation of halokinesis (salt mobilization) in a salt deposit. Tight, isoclinal folds verging to the NW and mechanical decoupling of this salt layer from its base suggest markedly different rheological behavior than the surrounding coarse-grained salt of the Z1 sequence. The deformation of this salt layer was attributed to the concomitant solution-precipitation creep and microcracking of halite grains. Microcracking is argued to significantly contribute to the pressure-solution creep and grain boundary sliding dominated deformation by decreasing the grain size of the deformed rock salt and extraction of the stored fluids in fluid inclusion trails by the transgranular microcracks.

 

Microstructure of the gamma-irradiated sample from the Upper Werra salt (Neuhof-Ellers salt mine, Germany). Note the purple colored cores of the grains with fluid inclusion trails surrounded by pale and dark blue mantles. The white lines represent healed microcracks that developed most frequently along the interface of the grain cores and the surrounding pale blue mantles at an angle of ~52° with the adjacent fluid inclusion trail. Scalebar is 0.2 mm.

Publications:

* Závada, P., Desbois, G., Schwedt, A., Lexa, O. & Urai, J. L. (2012). Extreme ductile deformation of fine-grained salt by coupled solution-precipitation creep and microcracking: Microstructural evidence from perennial zechstein sequence (neuhof salt mine, germany), Journal Of Structural Geology 37, 89–104, DOI: 10.1016/j.jsg.2012.01.024.

Team: Prokop Závada

Co-workers: Guillaume Desbois and Janos Urai (GED-RWTH Aachen), Ondrej Lexa (IPSG)