porosity; permeability; rheology; numerical modeling; rock deformation; microstructure
Gilgannon James, Poulet Thomas, Berger Alfons, Barnhoorn Auke, Herwegh Marco (2020), Dynamic Recrystallization Can Produce Porosity in Shear Zones, in Geophysical Research Letters
, 47(7), 1-10.
Akker Ismay Vénice, Kaufmann Josef, Desbois Guillaume, Klaver Jop, Urai Janos L., Berger Alfons, Herwegh Marco (2018), Multiscale porosity changes along the pro- and retrograde deformation path: an example from Alpine slates, in Solid Earth
, 9(5), 1141-1156.
Dielforder Armin, Vollstaedt Hauke, Vennemann Torsten, Berger Alfons, Herwegh Marco (2016), Linking megathrust earthquakes to brittle deformation in a fossil accretionary complex, in Nature Communications
, 6(1), 7504-7504.
(2016), Issue Information, in Tectonics
, 35(10), 2215-2215.
Peters Max, Veveakis Manolis, Poulet Thomas, Karrech Ali, Herwegh Marco, Regenauer-Lieb Klaus (2016), Boudinage as a material instability of elasto-visco-plastic rocks, in Journal of Structural Geology
, 78, 86-102.
Peters Max, Berger Alfons, Herwegh Marco, Regenauer-Lieb Klaus (2016), Strain localization in ductile rocks: A comparison of natural and simulated pinch-and-swell structures, in Tectonophysics
, 680, 140-154.
Sheet-silicate-rich lithologies are highly abundant in the Earth’s upper and middle crust. In a geodynamic context, they represent important rock types because (i) strain often is localized in these rocks due to their low rock strength at low to intermediate temperature conditions and (2) they serve as important fluid sources owing to water release with progressive recrystallization/compaction/metamorphic reaction. Improved knowledge on the interplay between fluid release and deformation is rather crucial to better understand what the rheological effect on the formation and evolution of crustal scale deformation (fold and thrust tectonics, shear zones) in these highly abundant upper to midcrustal rock types is. In the current study, two PhD students investigate both the structural aspect in nature (part A) and the theoretical rheological aspect (part C1). PhD study A establishes the link between dehydration and vein formation as well as the hydro-mechanical consequences in terms of seismic activity in accretionary complexes using the Infrahelvetic Flysch Units (IFU) as key area. PhD study C1 combined a new generation of energy-based elasto-visco-plastic modeling with microstructural processes. In close collaboration with the research group of Prof. Klaus Regenauer-Lieb (Australia), PhD student C1 developed the numerical tool and applied it to the question of strain localization in ductile deforming materials in general and the boudinage of calcite veins in particular. In the prolongation, we ask for an extension of 3 and 5 months for PhD students A and C1, respectively, to finalize their research articles and the PhD theses.After completion of the two theses, we would like to continue the project with two successor PhD studies (part B) and (part C2) within the three years SNF project period. In the case of part B, specific attention will be paid to the deformation processes and associated changes in microstructure and porosity in sheet-silicate-rich host rocks as a function of strain gradients and changing metamorphic conditions in the IFU. The study is based on detailed quantitative investigations at the scale of km down to µm. For this purpose low and high-end analytical techniques in the field of microstructures (e.g., light-microscopy, FEG-SEM; BIB-SEM) and geochemistry (Sr, O, C stable isotopes; EMPA, SIMS) have to be applied. Part B will greatly benefit from the findings of part A allowing an efficient and successful progress. Part C2 represents the continuation of part C1, enabling now the application of the newly developed and benchmarked numerical tool for the unraveling of the so far still unknown rheology of sheet-silicate-rich rock types. Here natural quartz and/or calcite boudins/folds of sheet-silicate-rich host rocks, with very well defined physico-chemical deformation conditions, serve as key samples to be quantitatively characterized (e.g. microstructures, deformation processes, geometries). The obtained physico-chemical conditions, the starting geometries, as well as the flow laws of the deformed quartz and/or calcite layers will serve as input parameters to solve for the unknown rheology of the sheet-silicate-rich matrix. The expected modeling results can be crosschecked with the observed natural structures. If successful, the approach can be applied to temperature ranges of several hundred °C to generate a flow law for sheet-silicate-rich rocks.In this sense, the suggested prolongation represents the logic continuation of the very successful first project period. This interdisciplinary and innovative research project will greatly benefit from collaboration between the different members of the research team at UniBe, UniL and FHZ but also the international collaboration with the colleagues in Sidney. With respect to the latter, joint projects at Sidney to be developed for integration of mineral reactions might be implemented in a later stage into parts B and C2. The suggested research project will have a broad impact in different disciplines of fundamental research as there are the localization of strain in sheet-silicate-rich rocks, the effect of fluid release on permeability and deformation (fracturing, earthquake nucleation) as well as in applied problems (e.g. radioactive waste deposits, CO2 sequestration, shale gas and deep seated geothermal energy).