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Geosciences
Special Issues
Microstructural Analyses of Fault Rocks
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Microstructural Analyses of Fault Rocks

A special issue of Geosciences (ISSN 2076-3263). This special issue belongs to the section "Structural Geology and Tectonics".

Deadline for manuscript submissions: closed (31 August 2022) | Viewed by 8239

Special Issue Editors

Dr. Martina Kirilova

E-Mail Website
Guest Editor
Institute for Geosciences, Johannes Gutenberg-Universität Mainz, J.-J.-Becher-Weg 21, 55128 Mainz, Germany
Interests: experimental rock deformation; carbonaceous material in fault zones
Dr. Ben Clennell

E-Mail Website
Guest Editor
The Commonwealth Scientific and Industrial Research Organisation (CSIRO), Bentley, WA 6102, Australia
Interests: geology; petrophysics; geophysics

Special Issue Information

Dear Colleagues,

This Special Issue of Geosciences focuses on the feedback between microstructures (such as fabrics, lattice-preferred orientation, grain sizes, pores, fractures, etc.) and deformation mechanisms in fault rocks. The microstructural characteristics of deformed rocks result from the conditions and processes that take place during brittle failure or ductile flow, thus recognizing them helps us to unravel the deformation history. Concurrently, the development of lattice-preferred orientation, grain size reduction, the microstructural organization of weak phases, pores and fractures, and the associated fluid–rock interactions control the rheological and kinematic behavior of fault rocks and can trigger further deformation mechanisms. Hence, characterizing fault rock microstructures can shed profound insights into the large-scale tectonic and thermo-chemical processes that control the evolution of active fault zones.

In this Special Issue, we invite contributions based on microstructural analyses from field observations, laboratory experiments on rocks or rock analogues (i.e. ice), imaging techniques and numerical modeling that aim to constrain deformation mechanisms in fault zones.

Dr. Martina Kirilova
Dr. Ben Clennell
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Geosciences is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • microstructural analyses
  • deformation processes
  • fault rocks
  • rheology
  • kinematics
  • strain localization

Published Papers (3 papers)

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Research

15 pages, 5196 KiB  
Article
The Memory of a Fault Gouge: An Example from the Simplon Fault Zone (Central Alps)
by Valentina Argante, David Colin Tanner, Christian Brandes, Christoph von Hagke and Sumiko Tsukamoto
Geosciences 2022, 12(7), 268; https://doi.org/10.3390/geosciences12070268 - 30 Jun 2022
Cited by 2 | Viewed by 2909
Abstract
Faut gouge forms at the core of the fault as the result of a slip in the upper brittle crust. Therefore, the deformation mechanisms and conditions under which the fault gouge was formed can document the stages of fault movement in the crust. [...] Read more.
Faut gouge forms at the core of the fault as the result of a slip in the upper brittle crust. Therefore, the deformation mechanisms and conditions under which the fault gouge was formed can document the stages of fault movement in the crust. We carried out a microstructural analysis on a fault gouge from a hanging-wall branch fault of the Simplon Fault Zone, a major low-angle normal fault in the European Alps. We use thin-section analysis, together with backscattered electron imaging and X-ray diffractometry (XRD), to show that a multistage history from ductile to brittle deformation within the fault gouge. We argue that this multistage deformation history is the result of continuous exhumation history from high to low temperature, along the Simplon Fault Zone. Because of the predominance of pressure solution and veining, we associated a large part of the deformation in the fault gouge with viscous-frictional behaviour that occurred at the brittle-ductile transition. Phyllosilicates and graphite likely caused fault lubrication that we suggested played a role in localizing slip along this major low-angle normal fault. Full article
(This article belongs to the Special Issue Microstructural Analyses of Fault Rocks)
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18 pages, 5651 KiB  
Article
Ductile Shearing and Focussed Rejuvenation: Records of High-P (eo-)Alpine Metamorphism in the Variscan Lower Crust (Serre Massif, Calabria—Southern Italy)
by Vincenzo Festa, Annamaria Fornelli, Francesca Micheletti, Richard Spiess and Fabrizio Tursi
Geosciences 2022, 12(5), 212; https://doi.org/10.3390/geosciences12050212 - 17 May 2022
Cited by 1 | Viewed by 1672
Abstract
In the present study, we unveil the real significance of mylonitic reworking of the polymetamorphic crystalline basement in the Serre Massif of Calabria (Southern Italy). We use a multidisciplinary approach to comprehend the structural, microstructural and petrologic changes that occurred along a, so [...] Read more.
In the present study, we unveil the real significance of mylonitic reworking of the polymetamorphic crystalline basement in the Serre Massif of Calabria (Southern Italy). We use a multidisciplinary approach to comprehend the structural, microstructural and petrologic changes that occurred along a, so far, not much considered shear zone affecting the Variscan lower crustal rocks. It was never before studied in detail, although some late Cretaceous ages were reported for these mylonites, suggesting that this shear zone is of prime importance. Our observations reveal now that the formation of the new structural fabric within the shear zone was accompanied by changes in mineral assemblages, in a dominant compressive tectonic regime. During this tectono-metamorphic event, high-P mylonitic mineral assemblages were stabilized, consisting of chloritoid, kyanite, staurolite, garnet and paragonite, whereas plagioclase became unstable. Average peak P–T conditions of 1.26–1.1 GPa and 572–626 °C were obtained using THERMOCALC software. These data question (i) that the Serre Massif represents an undisturbed continuous section of the Variscan crust, as generally suggested in the literature, and (ii) highlight the role of (eo-)Alpine high-P tectonics in the Serre Massif, recorded within mylonite zones, where the Variscan basement was completely rejuvenated. Full article
(This article belongs to the Special Issue Microstructural Analyses of Fault Rocks)
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19 pages, 5477 KiB  
Article
Electrical Properties and Anisotropy of Schists and Fault Rocks from New Zealand’s Southern Alps under Confining Pressure
by Emma-Katherine Kluge, Virginia Toy and David Lockner
Geosciences 2022, 12(3), 121; https://doi.org/10.3390/geosciences12030121 - 04 Mar 2022
Cited by 1 | Viewed by 2794
Abstract
Magnetotelluric models spanning the Pacific–Australian Plate boundary in New Zealand’s South Island indicate a localized zone of low electrical resistivity that is spatially coincident with the ductile mid-crustal part of the Alpine Fault Zone (AFZ). We explored the source of this anomaly by [...] Read more.
Magnetotelluric models spanning the Pacific–Australian Plate boundary in New Zealand’s South Island indicate a localized zone of low electrical resistivity that is spatially coincident with the ductile mid-crustal part of the Alpine Fault Zone (AFZ). We explored the source of this anomaly by measuring the electrical properties of samples collected from surface outcrops approaching the AFZ that have accommodated a gradient of systematic strain and deformation conditions. We investigated the effects of tectonite fabric, fluid saturated pore/fracture networks and surface conductivity on the bulk electrical response and the anisotropy of resistivity measured under increasing confining pressures up to 200 MPa. We find that porosity and resistivity increase while porosity and the change in anisotropy of resistivity with confining pressure (δ (ρ‖/ρ⊥)/δ (peff)) decreases approaching the AFZ, indicating the electrical response is controlled by pore fluid conductivity and modified during progressive metamorphism. Conversely, Alpine mylonites exhibit relatively low resistivities at low porosities, and lower δ (ρ‖/ρ⊥)/δ (peff) than the schists. These findings indicate a transition in both the porosity distribution and electrical charge transport processes in rocks that have experienced progressive grain size reduction and mixing of phases during development of mylonitic fabrics due to creep shear strain within the AFZ. Full article
(This article belongs to the Special Issue Microstructural Analyses of Fault Rocks)
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