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The role of sheet silicate-rich rocks during mountain building processes

English title The role of sheet silicate-rich rocks during mountain building processes
Applicant Herwegh-Züger Marco
Number 162340
Funding scheme Project funding (Div. I-III)
Research institution Institut für Geologie Universität Bern
Institution of higher education University of Berne - BE
Main discipline Geology
Start/End 01.01.2016 - 30.09.2020
Approved amount 661'901.00
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All Disciplines (2)

Discipline
Geology
Mineralogy

Keywords (6)

porosity; permeability; rheology; numerical modeling; rock deformation; microstructure

Lay Summary (German)

Lead
Schichtsilikat-reiche Gesteine sind wichtig für gebirgsbildende Prozesse, da sie häufig als mechanische ‚Schmiermittel’ entlang von Bewegungszonen agieren. Dies resultiert zum einen aufgrund der Kristallstruktur der Schichtsilikate. Zum anderen können schichtsilikatreiche Gesteine Wasser aus Porenräumen und der Kristallstruktur frei setzen, was zu erhöhtem Porenfluiddruck und somit zu Materialversagen führen kann. Im Rahmen der vorliegenden Arbeit werden wir diese mechanischen Schwächungsprozesse durch Feldstudien und numerische Modellierungen untersuchen.
Lay summary

Inhalt, Ziele und erste Resultate der ersten Projektperiode

Gesteine des Nordhelvetischen Flysches (Glarner Alpen) wurden als Vertreter eines Paleoakkretionskeiles (Front eines aktiven Gebirges) im Detail untersucht. Basierend auf mikrostrukturellen, geochemischen und mechanischen Betrachtungen kann dokumentiert werden, dass das mikrostrukturelle Umwandlungen und ein damit assoziiertes Freisetzen von Fluiden einen grossen Einfluss auf das seismisch-aseismische Deformationsverhalten hat. Die räumliche und zeitliche Abfolge der beobachteten Deformationsstrukturen korreliert exzellent mit seismischer Aktivität, wie sie heute in aktiven Akkretionskeilen gemessen wird. In der nächsten Projektperiode sollen der Einfluss der Deformation auf die Mikrostrukturen und Deformationsprozesse gelegt werden.

Im Hinblick auf numerische Modellierungen werden elasto-visco-plastische Simulationscodes verwendet in welche thermodynamische Grundprinzipien integriert sind. Es wird die Deformationsart (Boudinage, Faltung, Vorformungslokalisierung) als Funktion der entstehenden Deformationsenergie untersucht. Mit Hilfe dieses Ansatzes und seiner Anwendung auf natürliche Gesteine soll das Fliessverhalten schichtsilikat-reicher Gesteine im Erdinnern entschlüsselt werden.

 

Wissenschaftliche und gesellschaftliche Relevanz

Die neuen Erkenntnisse werden zu einem besseren Verständnis des Deformationsverhaltens mechanischer weicher, schichtsilikat-reicher Gesteine beitragen. Dieses Wissen ist für ein besseres Verständnis von Gebirgsbildungsprozessen, der Entschlüsselung von Erdbebenmechanismen, dem Nutzen von Tiefengeothermie, der Tiefenlagerung von radioaktivem Abfall als auch der Gas-und Ölexploration wichtig.

 

Direct link to Lay Summary Last update: 04.01.2016

Responsible applicant and co-applicants

Employees

Publications

Publication
Dynamic Recrystallization Can Produce Porosity in Shear Zones
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.
Multiscale porosity changes along the pro- and retrograde deformation path: an example from Alpine slates
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.
Linking megathrust earthquakes to brittle deformation in a fossil accretionary complex
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.
Issue Information
(2016), Issue Information, in Tectonics, 35(10), 2215-2215.
Boudinage as a material instability of elasto-visco-plastic rocks
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.
Strain localization in ductile rocks: A comparison of natural and simulated pinch-and-swell structures
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.

Collaboration

Group / person Country
Types of collaboration
University of Lausanne, Prof. Thorsten Vennemann Switzerland (Europe)
- Publication
- Research Infrastructure
QTU, Dr. Christoph Schrank Australia (Oceania)
- Publication
- Research Infrastructure
EMPA; Dr. Josef Kaufmann Switzerland (Europe)
- Publication
- Research Infrastructure
Kyoto University, Prof. Horst Zwingmann Japan (Asia)
- Publication
- Research Infrastructure
RWTH Aachen, Prof. Janos Urai Germany (Europe)
- Publication
- Research Infrastructure
Bern University, Prof. Dr. Thomas Pettke Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
University of New South Wales, Prof. Klaus Regenauer-Lieb Australia (Oceania)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
CSIRO Perth, Dr. Thomas Poulet Australia (Oceania)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Edinburg University, Dr. Florian Fusseis Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Associated projects

Number Title Start Funding scheme
178785 Fluids and new fluid tracers in water under-saturated continental crust: From rifting to tectonic inversion 01.09.2018 Project funding (Div. I-III)
170738 New Ionpolisher for high-end surface preparation of composite materials 01.12.2016 R'EQUIP
169055 Structure and evolution of an antiformal nappe stack (Aar massif, Central Alps): Formation of mechanical anisotropies and their bearing on natural risks 01.10.2016 Project funding (Div. I-III)
144381 The role of sheet silicate-rich rocks during mountain building processes 01.01.2013 Project funding (Div. I-III)
149385 Structure and evolution of an antiformal nappe stack (Aar massif, Central Alps): Formation of mechanical anisotropies and their bearing on natural risks 01.10.2013 Project funding (Div. I-III)
177026 Re-equiping the noble gas laboratory to perform state of the art science, University of Geneva 01.03.2018 R'EQUIP

Abstract

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).
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