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Hamers MF, Niemeijer AR, Drury MR. Cathodoluminescence as a tracing technique for quartz precipitation in low velocity shear experiments. Sci Rep 2023; 13:10236. [PMID: 37353517 DOI: 10.1038/s41598-023-37052-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 06/15/2023] [Indexed: 06/25/2023] Open
Abstract
Two simulated gouges (a pure quartz and a quartz-muscovite mixture) were experimentally deformed in a ring shear apparatus at a constant low velocity under hydrothermal conditions favourable for dissolution-precipitation processes. Microstructural analysis using scanning electron microscope cathodoluminescence imaging and cathodoluminescence spectroscopy combined with chemical analysis showed that quartz dissolution and precipitation occurred in both experiments. The starting materials and deformation conditions were chosen so that dissolution-precipitation microstructures could be unambiguously identified from their cathodoluminescence signal. Precipitated quartz was observed as blue luminescent fracture fills and overgrowths with increased Al content relative to the original quartz. In the pure quartz gouge, most of the shear deformation was localized on a boundary-parallel slip surface. Sealing of fractures in a pulverized zone directly adjacent to the slip surface may have helped keeping the deformation localized. In the quartz-muscovite mixture, some evidence was observed of shear-accommodating precipitation of quartz in strain shadows, but predominantly in fractures, elongating the original grains. Precipitation of quartz in fractures implies that the length scale of diffusive mass transfer in frictional-viscous flow is shorter than the length of the quartz domains. Additionally, fracturing might play a more important role than generally assumed. Our results show that cathodoluminescence, especially combined with chemical analysis, is a powerful tool in microstructural analyses of experimentally deformed quartz-bearing material and visualizing quartz precipitation.
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Affiliation(s)
- Maartje F Hamers
- Department of Earth Sciences, Utrecht University, Princetonlaan 8a, 3584 CB, Utrecht, The Netherlands.
| | - André R Niemeijer
- Department of Earth Sciences, Utrecht University, Princetonlaan 8a, 3584 CB, Utrecht, The Netherlands
| | - Martyn R Drury
- Department of Earth Sciences, Utrecht University, Princetonlaan 8a, 3584 CB, Utrecht, The Netherlands
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Forsyth PWF, Hayward KS, Roberts LE, Cox SF, Shaddock DA, Slagmolen BJJ. Large dynamic range, high resolution optical heterodyne readout for high velocity slip events. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:064503. [PMID: 35778025 DOI: 10.1063/5.0082970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 05/13/2022] [Indexed: 06/15/2023]
Abstract
We present a free-space optical displacement sensor for measuring geological slip event displacements within a laboratory setting. This sensor utilizes a fiberized Mach-Zehnder based optical heterodyne system coupled with a digital phase lock loop, providing a large dynamic range (multiple centimeters), high displacement resolution (with an amplitude spectral density of <10-10 m/Hz for frequencies above 100 Hz), and high velocity tracking capabilities (up to 4.96 m/s). This displacement sensor is used to increase the displacement and the time sensitivity for measuring laboratory-scale earthquakes induced in geological samples by using a triaxial compression apparatus. The sensor architecture provides an improved displacement and time resolution for the millisecond-duration slip events, at high containment and loading pressure and high temperatures. Alternatively, the sensor implementation can be used for other non-contact displacement readouts that required high velocity tracking with low noise and large dynamic range sensing. We use 13 high-velocity slip events in Fontainebleau sandstone to show the large dynamic range displacement tracking ability and displacement amplitude spectral densities to demonstrate the optical readout's unique sensing capabilities.
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Affiliation(s)
- Perry W F Forsyth
- ARC Centre of Excellence for Gravitational Wave Discovery, Centre for Gravitational Astrophysics, Research School of Physics, and of Astronomy and Astrophysics, The Australian National University, Canberra, Acton 2601, Australia
| | - Kathryn S Hayward
- Research School of Earth Sciences, The Australian National University, Canberra, Acton 2601, Australia
| | - Lyle E Roberts
- ARC Centre of Excellence for Gravitational Wave Discovery, Centre for Gravitational Astrophysics, Research School of Physics, and of Astronomy and Astrophysics, The Australian National University, Canberra, Acton 2601, Australia
| | - Stephen F Cox
- Research School of Earth Sciences, The Australian National University, Canberra, Acton 2601, Australia
| | - Daniel A Shaddock
- ARC Centre of Excellence for Gravitational Wave Discovery, Centre for Gravitational Astrophysics, Research School of Physics, and of Astronomy and Astrophysics, The Australian National University, Canberra, Acton 2601, Australia
| | - Bram J J Slagmolen
- ARC Centre of Excellence for Gravitational Wave Discovery, Centre for Gravitational Astrophysics, Research School of Physics, and of Astronomy and Astrophysics, The Australian National University, Canberra, Acton 2601, Australia
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Menegon L, Campbell L, Mancktelow N, Camacho A, Wex S, Papa S, Toffol G, Pennacchioni G. The earthquake cycle in the dry lower continental crust: insights from two deeply exhumed terranes (Musgrave Ranges, Australia and Lofoten, Norway). PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2021; 379:20190416. [PMID: 33517876 PMCID: PMC7898122 DOI: 10.1098/rsta.2019.0416] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 09/14/2020] [Indexed: 05/31/2023]
Abstract
This paper discusses the results of field-based geological investigations of exhumed rocks exposed in the Musgrave Ranges (Central Australia) and in Nusfjord (Lofoten, Norway) that preserve evidence for lower continental crustal earthquakes with focal depths of approximately 25-40 km. These studies have established that deformation of the dry lower continental crust is characterized by a cyclic interplay between viscous creep (mylonitization) and brittle, seismic slip associated with the formation of pseudotachylytes (a solidified melt produced during seismic slip along a fault in silicate rocks). Seismic slip triggers rheological weakening and a transition to viscous creep, which may be already active during the immediate post-seismic deformation along faults initially characterized by frictional melting and wall-rock damage. The cyclical interplay between seismic slip and viscous creep implies transient oscillations in stress and strain rate, which are preserved in the shear zone microstructure. In both localities, the spatial distribution of pseudotachylytes is consistent with a local (deep) source for the transient high stresses required to generate earthquakes in the lower crust. This deep source is the result of localized stress amplification in dry and strong materials generated at the contacts with ductile shear zones, producing multiple generations of pseudotachylyte over geological time. This implies that both the short- and the long-term rheological evolution of the dry lower crust typical of continental interiors is controlled by earthquake cycle deformation. This article is part of a discussion meeting issue 'Understanding earthquakes using the geological record'.
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Affiliation(s)
- Luca Menegon
- The Njord Centre, Department of Geoscience, University of Oslo, 1048 Blindern, Norway
- School of Geography, Earth and Environmental Sciences, University of Plymouth, Drake Circus, PL4 8AA Plymouth, UK
| | - Lucy Campbell
- School of Geography, Earth and Environmental Sciences, University of Plymouth, Drake Circus, PL4 8AA Plymouth, UK
| | - Neil Mancktelow
- Department of Earth Sciences, ETH Zurich, 8092 Zurich, Switzerland
| | - Alfredo Camacho
- Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - Sebastian Wex
- Department of Earth Sciences, ETH Zurich, 8092 Zurich, Switzerland
| | - Simone Papa
- Department of Geosciences, University of Padova, Via Gradenigo 6, 35131 Padua, Italy
| | - Giovanni Toffol
- Department of Geosciences, University of Padova, Via Gradenigo 6, 35131 Padua, Italy
| | - Giorgio Pennacchioni
- Department of Geosciences, University of Padova, Via Gradenigo 6, 35131 Padua, Italy
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Acosta M, Passelègue FX, Schubnel A, Violay M. Dynamic weakening during earthquakes controlled by fluid thermodynamics. Nat Commun 2018; 9:3074. [PMID: 30082789 PMCID: PMC6079085 DOI: 10.1038/s41467-018-05603-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 07/12/2018] [Indexed: 11/09/2022] Open
Abstract
Earthquakes result from weakening of faults (transient decrease in friction) during co-seismic slip. Dry faults weaken due to degradation of fault asperities by frictional heating (e.g. flash heating). In the presence of fluids, theoretical models predict faults to weaken by thermal pressurization of fault fluid. However, experimental evidence of rock/fluid interactions during dynamic rupture under realistic stress conditions remains poorly documented. Here we demonstrate that the relative contribution of thermal pressurization and flash heating to fault weakening depends on fluid thermodynamic properties. Our dynamic records of laboratory earthquakes demonstrate that flash heating drives strength loss under dry and low (1 MPa) fluid pressure conditions. Conversely, flash heating is inhibited at high fluid pressure (25 MPa) because water's liquid-supercritical phase transition buffers frictional heat. Our results are supported by flash-heating theory modified for pressurized fluids and by numerical modelling of thermal pressurization. The heat buffer effect has maximum efficiency at mid-crustal depths (~2-5 km), where many anthropogenic earthquakes nucleate.
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Affiliation(s)
- M Acosta
- Laboratory of Experimental Rock Mechanics (LEMR), École Polytechnique Fédérale de Lausanne (EPFL), Station 18, CH-1015, Lausanne, Switzerland.
| | - F X Passelègue
- Laboratory of Experimental Rock Mechanics (LEMR), École Polytechnique Fédérale de Lausanne (EPFL), Station 18, CH-1015, Lausanne, Switzerland.,School of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
| | - A Schubnel
- Laboratoire de Géologie, CNRS UMR 8538, École Normale Supérieure, 75005, Paris, France
| | - M Violay
- Laboratory of Experimental Rock Mechanics (LEMR), École Polytechnique Fédérale de Lausanne (EPFL), Station 18, CH-1015, Lausanne, Switzerland
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