Articles | Volume 11, issue 3
https://doi.org/10.5194/se-11-807-2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/se-11-807-2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
07 May 2020
Research article |
| 07 May 2020
| 07 May 2020
Magnetic properties of pseudotachylytes from western Jämtland, central Swedish Caledonides
Bjarne S. G. Almqvist
CORRESPONDING AUTHOR
Department of Earth Sciences, Geophysics, Villavägen 16, 752 36
Uppsala, Sweden
Hagen Bender
Department of Geological Sciences, Stockholm University, 106 91
Stockholm, Sweden
Amanda Bergman
Department of Geological Sciences, Stockholm University, 106 91
Stockholm, Sweden
Ramböll Sverige AB, Box 17009, Krukmakargatan 21, 104 62
Stockholm, Sweden
Uwe Ring
Department of Geological Sciences, Stockholm University, 106 91
Stockholm, Sweden
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Martijn P. A. van den Ende, Marco M. Scuderi, Frédéric Cappa, and Jean-Paul Ampuero
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The injection of fluids (like wastewater or CO2) into the subsurface could cause earthquakes when existing geological faults inside the reservoir are (re-)activated. To assess the hazard associated with this, previous studies have conducted experiments in which fluids have been injected into centimetre- and decimetre-scale faults. In this work, we analyse and model these experiments. To this end, we propose a new approach through which we extract the model parameters that govern slip on faults.
Berend A. Verberne, Martijn P. A. van den Ende, Jianye Chen, André R. Niemeijer, and Christopher J. Spiers
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In this study, we conducted 3-D numerical simulations of fluid flow in synthetically generated fractures that statistically reflect geometries of naturally occurring fractures. We introduced a non-dimensional characterization scheme to relate fracture permeabilities estimated from the numerical simulations to their geometries in a unique manner. By that, we refined the scaling law for fracture permeability, which can be easily integrated into discrete-fracture-network (DFN) modeling approaches.
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Rock-forming minerals behave elastically, a property that controls their ability to support stress and strain, controls the transmission of seismic waves, and influences subsequent permanent deformation. Minerals are intrinsically anisotropic in their elastic properties; that is, they have directional variations that are related to the crystal lattice. We explore this directionality and present new ways of visualising it. We hope this will enable further advances in understanding deformation.
Mathieu Soret, Philippe Agard, Benoît Ildefonse, Benoît Dubacq, Cécile Prigent, and Claudio Rosenberg
Solid Earth, 10, 1733–1755, https://doi.org/10.5194/se-10-1733-2019, https://doi.org/10.5194/se-10-1733-2019, 2019
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This study sheds light on the mineral-scale mechanisms controlling the progressive deformation of sheared amphibolites from the Oman metamorphic sole during subduction initiation and unravels how strain is localized and accommodated in hydrated mafic rocks at high temperature conditions. Our results indicate how metamorphic reactions and pore-fluid pressures driven by changes in pressure–temperature conditions and/or water activity control the rheology of mafic rocks.
Camille Parlangeau, Alexandre Dimanov, Olivier Lacombe, Simon Hallais, and Jean-Marc Daniel
Solid Earth, 10, 307–316, https://doi.org/10.5194/se-10-307-2019, https://doi.org/10.5194/se-10-307-2019, 2019
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Calcite twinning is a common deformation mechanism that mainly occurs at low temperatures. Twinning activation appears at a critical strength value, which is poorly documented and still debated. Temperature is known to influence twin thickness and shape; however, few studies have been conducted on calcite deformation at low temperatures. The goal of this work is to determine if thickness is mainly due to high temperatures and to establish the validity of a threshold twinning activation value.
Cited articles
Beckholmen, M.: Mylonites and pseudotachylites associated with thrusting of
the Köli Nappes, Tännforsfältet, Central Swedish Caledonides,
Geologiska Föreningen i Stockholm Förhandlingar, 104, 23–32,
1982.
Beckholmen, M.: The deformation sequence in the
Häggsjö-Musvalttjärnen-Rensjönäset area in western
Jämtland, Swedish Caledonides, Geologiska Föreningen i Stockholm
Förhandlingar, 105, 119–130, 1983.
Beckholmen, M.: Structural and Metamorphic Zonation in
Tännforsfältet Western Jämtland, Swedish Caledonides, Univ.
Stockholm, 82 pp., 1984.
Bender, H., Ring, U., Almqvist, B. S. G., Grasemann, B., and Stephens, M. B.:
Metamorphic zonation by out-of-sequence thrusting at back-stepping
subduction zones: Sequential accretion of the Caledonian internides, Central
Sweden, Tectonics, 37, 3545–3576, https://doi.org/10.1029/2018TC005088, 2018.
Bender, H., Glodny, J., and Ring, U.: Absolute timing of Caledonian orogenic wedge assembly, Central Sweden, constrained by Rb-Sr multi-mineral isochron data, Lithos, 344, 339–359, 2019.
Bergman, A.: The Pseudotachylites of Tännforsfältet,Western
Jämtland, Swedish Caledonides, Stockholm University, 75 pp., 2017.
Bergman, S. and Sjöström, H.: Accretion and lateral extension in an
orogenic wedge: Evidence from a segment of the Seve-Köli terrane
boundary, central Scandinavian Caledonides, J. Struct. Geol., 19,
1073–1091, 1997.
Borradaile, G.: Anisotropy of magnetic susceptibility: rock composition
versus strain, Tectonophysics, 138, 327–329, 1987.
Borradaile, G. J. and Henry, B.: Tectonic applications of magnetic
susceptibility and its anisotropy, Earth Sci. Rev., 42, 49–93, 1997.
Borradaile, G. J. and Jackson, M.: Structural geology, petrofabrics and
magnetic fabrics (AMS, AARM, AIRM), J. Struct. Geol., 32, 1519–1551,
https://doi.org/10.1016/j.jsg.2009.09.006, 2010.
Butler, R. F.: Paleomagnetism: Magnetic domains to geologic terranes,
Electron. Ed., 238 pp., 1998.
Cañón-Tapia, E. and Castro, J.: AMS measurements on obsidian from
the Inyo Domes, CA: A comparison of magnetic and mineral preferred
orientation fabrics, J. Volcanol. Geotherm. Res., 134, 169–182, 2004.
Cowan, D. S.: Do faults preserve a record of seismic slip?, A field
geologist's opinion, J. Struct. Geol., 21, 995–1001, 1999.
Dearing, J. A., Dann, R. J. L., Hay, K., Lees, J. A., Loveland, P. J., Maher,
B. A., and O'Grady, K.: Frequency-dependent susceptibility measurements of
environmental materials, Geophys. J. Int., 124, 228–240, 1996.
Di Toro, G. and Pennacchioni, G.: Superheated friction-inducde melts in
zoned pseudotachylytes within the Adamello tonalites (Italian Southern
Alps), J. Struct. Geol., 26, 1783–1801, 2004.
Di Toro, G., Nielsen, S., and Pennacchioni, G.: Earthquake rupture dynamics
frozen in exhumed ancient faults, Nature, 436, 1009–1012,
https://doi.org/10.1038/nature03910, 2005.
Ernst, R. E. and Baragar, W. R. A.: Evidence from magnetic fabric for the
flow pattern of magma in the Mackenzie giant radiating dyke swarm, Nature,
356, 511–513, 1992.
Ferré, E. C., Geissman, J. W., and Zechmeister, M. S.: Magnetic
properties of fault pseudotachylytes in granites, J. Geophys. Res.-Sol. Ea., 117, 1–25, https://doi.org/10.1029/2011JB008762, 2012.
Ferré, E. C., Geissman, J. W., Demory, F., Gattacceca, J., Zechmeister,
M. S., and Hill, M. J.: Coseismic magnetization of fault pseudotachylytes: 1. Thermal demagnetization experiments, J. Geophys. Res.-Sol. Ea., 119,
6113–6135, 2014.
Ferré, E. C., Geissman, J. W., Chauvet, A., Vauchez, A., and Zechmeister,
M. S.: Focal mechanism of prehistoric earthquakes deduced from
pseudotachylyte fabric, Geology, 43, 531–534, https://doi.org/10.1130/G36587.1,
2015.
Fossen, H.: Structural Geology, Cambridge University Press, Cambridge, 463 pp.,
2010.
Fukuchi, T.: Strong ferrimagnetic resonance signal and magnetic
susceptibility of the Nojima pseudotachylyte in Japan and their implication
for coseismic electromagnetic changes, J. Geophys. Res.-Sol. Ea.,
108, 1–8, https://doi.org/10.1029/2002JB002007, 2003.
Gee, D. G., Lobkowicz, M., and Singh, S.: Late Caledonian extension in the
scandinavian Caledonides-the Røragen Detachment revisited,
Tectonophysics, 231, 139–143, https://doi.org/10.1016/0040-1951(94)90126-0, 1994.
Hirt, A. M. and Almqvist, B. S. G.: Unraveling magnetic fabrics, Int. J.
Earth Sci., 101, 613–624, https://doi.org/10.1007/s00531-011-0664-0, 2012.
Hrouda, F.: Models of frequency-dependent susceptibility of rocks and soils
revisited and broadened, Geophys. J. Int., 187, 1259–1269, 2011.
Hunt, C. P., Moskowitz, B. M., and Banarjee, S. K.: Magnetic properties of rocks
and minerals, Rock Physics and Phase Relations, A Handbook of Physical
Constants, AGU Reference Shelf, 3, 189–204, 1995.
Jelinek, V.: Characterization of the magnetic fabric of rocks,
Tectonophysics, 79, 63–67, 1981.
Jelínek, V.: Measuring anisotropy of magnetic susceptibility on a slowly spinning specimen – basic theory, AGICO Print No. 10. (leaflet), 27 pp., 1996.
Kirkpatrick, J. D. and Rowe, C. D.: Disappearing ink: How pseudotachylytes are
lost from the rock record, J. Struct. Geol., 52, 183–198, 2013.
Kirkpatrick, J. D., Dobson, K. J., Mark, D. F., Shipton, Z. K., Brodsky, E. E., and Stuart, F. M.: The depth of pseudotachylyte formation from
detailed thermochronology and constraints on coseismic stress drop
variability, J. Geophys. Res., 117, B06406, doi:10.1029/2011JB008846, 2012.
Lin, A.: Microlite morphology and chemistry in pseudotachylite, from the
Fuyun Fault Zona, China, J. Geol., 102, 317–329, 1994.
Lin, A.: Fossil Earthquakes: The Formation and Preservation of
Pseudotachylytes, Spinger, 348 pp., 2008.
Magloughlin, J. F. and Spray, J. G.: Frictional melting processes and
products in geological materials: introduction and discussion,
Tectonophysics, 204, 197–204, 1992.
Marrett, R. and Allmendinger, R. W.: Kinematic analysis of fault-slip data,
J. Struct. Geol., 12, 973–986, https://doi.org/10.1016/0191-8141(90)90093-E, 1990.
Martín-Hernández, F. and Hirt, A. M.: The anisotropy of magnetic
susceptibility in biotite, muscovite and chlorite single crystals,
Tectonophysics, 367, 13–28, 2003.
Nakamura, N., Hirose, T., and Borradaile, G. J.: Laboratory verification of
submicron magnetite production in pseudotachylytes: Relevance for
paleointensity studies, Earth Planet. Sci. Lett., 201, 13–18,
https://doi.org/10.1016/S0012-821X(02)00704-5, 2002.
Paterson, G. A., Zhao, X., Jackson, M., and Heslop, D.: Measuring, processing,
and analyzing hysteresis data, Geochem. Geophy. Geosy., 19, 1925–1945,
2018.
Rowe, C. D. and Griffith, W. A.: Do faults preserve a record of seismic
slip: A second opinion, J. Struct. Geol., 78, 1–26,
https://doi.org/10.1016/j.jsg.2015.06.006, 2015.
Scott, R. G. and Spray, J. G.: Magnetic
fabric constraints on friction melt flow regimes and ore emplacement
direction within the South Range Breccia Belt, Sudbury Impact Structure,
Tectonophysics, 307, 163–189, https://doi.org/10.1016/S0040-1951(99)00124-9,
1999.
Sibson, R. H.: Generation of pseudotachylyte by ancient seismic faulting,
Geophys. J. Int., 43, 775–794, 1975.
Sibson, R. and Toy, V.: The Habitat of Fault-Generated Pseudotachylyte:
Presence vs. Absence of Friction-Melt, in: Earthquakes: Radiated Energy and the Physics of Faulting, Geophysical Monograph Series 170, American Geophysical Union, doi:10.1029/170GM16, 2006.
Tarling, D. and Hrouda, F.: Magnetic anisotropy of rocks, Springer Science
& Business Media, 217 pp., 1993.
Tauxe, L.: Essentials of paleomagnetism, First Edit., University of
California Press, Berkeley, Los Angeles, London, 489 pp., 2010.
Zhang, L., Haibing, L., Sun, Z., Chou, Y.-M., Cao, Y., and Wang, H.: Metallic
iron formed by melting: A new mechanism for magnetic highs in
pseudotachylyte, Geology, 46, 779–782, 2018.
Short summary
Rocks in fault zones can melt during earthquakes. The geometry and magnetic properties of such earthquake-melted rocks from Jämtland, central Sweden, show that they formed during Caledonian mountain building in the Palaeozoic. The small sample size (~0.2 cm3) used in this study is unconventional in studies of magnetic anisotropy and introduces challenges for interpretations. Nevertheless, the magnetic properties help shed light on the earthquake event and subsequent alteration of the rock.
Rocks in fault zones can melt during earthquakes. The geometry and magnetic properties of such...
