Strong ferrimagnetic resonance signal and magnetic susceptibility of the Nojima pseudotachylyte in Japan and their implication for coseismic electromagnetic changes

Fukuchi, Tatsuro

doi:10.1029/2002jb002007

Cited by 24 publications

(48 citation statements)

References 47 publications

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“…[56] In general, fault pseudotachylytes have a magnetic susceptibility that is significantly higher (up to 250 times) than their immediate host rock [e.g., Nakamura and Nagahama, 2001;Fukuchi, 2003;Ferré et al, 2005;Hirono et al, 2006]. However, this increase, generally attributed to the breakdown of ferromagnesian silicates and subsequent formation of fine-grained magnetite, is not systematic [Zechmeister et al, 2007;Molina Garza et al, 2009].…”

Section: Importance Of Variations In Magnetic Susceptibility In Faultmentioning

confidence: 99%

“…In general, the most common primary ferromagnetic (s.l.) minerals in fault pseudotachylytes are magnetite (Fe 3 O 4 ), and maghemite, (g-Fe 2 O 3 ) [Nakamura and Nagahama, 2001;Fukuchi, 2003;Ferré et al, 2005;Hirono et al, 2006;Zechmeister et al, 2007;Molina Garza et al, 2009]. Post-seismic alteration of these minerals generally leads to formation of more oxidized phases: At Santa Rosa, opaque grains in the pseudotachylyte, identified using optical and electron microscopy, are dominated by euhedral magnetite grains (<5 mm).…”

Section: Ferromagnetic Mineralsmentioning

confidence: 99%

“…A number of reactions, driven by frictional heating, may account for the observed increases of magnetic susceptibility in fault rocks. Two examples of such reactions are: (R 1 ) siderite ⇒ pyrite or pyrrhotite ⇒ magnetite, under low oxygen fugacity [ f O 2 ] (Chelungpu Fault [Tanikawa et al, 2008]); (R 2 ) goethite ⇒ hematite, under higher f O 2 (Nojima Fault [Fukuchi et al, 2005] Fukuchi, 2003;Petrík et al, 2003]. However, other factors such as host rock composition and degree of melting also affect f O 2 and thus the magnetic properties of pseudotachylytes [Henkel and Reimold, 2002;Nakamura and Iyeda, 2005;Zechmeister, 2005;Hirono et al, 2006].…”

Section: Importance Of Variations In Magnetic Susceptibility In Faultmentioning

confidence: 99%

“…These mid-Proterozoic and Caledonian veins, from a few millimeters up to several meters thick, reveal a strong remanent magnetization (Q ratios = 10 to 100), carried by single domain (SD) to pseudo-single domain (PSD) magnetite grains. Fukuchi [2003] and Fukuchi et al [2005] studied pseudotachylytes from the Nojima Fault, Japan, responsible for the devastating 1995 Kobe earthquake (M = 7.2). These veins originated from cataclasis and not from frictional melting [Lin, 2001].…”

Section: Natural Pseudotachylytesmentioning

confidence: 99%

“…[4] Nevertheless, recent investigations on borehole cores through the Nojima Fault, Japan, and the Chelungpu Fault, Taiwan [Fukuchi, 2003;Fukuchi et al, 2005;Hirono et al, 2006] revealed that magnetization acquisition processes could be more complex than a simple TRM and could also include a chemical remanent magnetization (CRM) as a major component of the NRM. Although TRM acquisition is inevitably coseismic due to the quasi instantaneous cooling of the pseudotachylyte melt [Nakamura et al, 2002;Ferré et al, 2005], the timing of CRM acquisition is less well understood.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic properties of fault pseudotachylytes in granites

Ferré¹,

Geissman²,

Zechmeister³

2012

J. Geophys. Res.

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[1] We investigate the petrographic, geochemical and magnetic properties of fault pseudotachylytes formed by frictional melting in granitic rocks from Southern California, the Italian Alps and Kyushyu, Japan. The main magnetic remanence carriers are mixtures of grain sizes of fine grained magnetite. These ferrimagnetic grains record a stable, multicomponent magnetization that consists of one or more of the following: coseismic thermal remanent magnetization, coseismic lightning isothermal remanent magnetization and post-seismic chemical remanent magnetization. Fault pseudotachylytes from the three localities display contrasting magnetic properties, which suggests that oxygen fugacity and host rock composition ultimately control the magnetic assemblage.

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Section: Importance Of Variations In Magnetic Susceptibility In Faultmentioning

confidence: 99%

Section: Ferromagnetic Mineralsmentioning

confidence: 99%

Section: Importance Of Variations In Magnetic Susceptibility In Faultmentioning

confidence: 99%

Section: Natural Pseudotachylytesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Magnetic properties of fault pseudotachylytes in granites

Ferré¹,

Geissman²,

Zechmeister³

2012

J. Geophys. Res.

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Coseismic magnetization of fault pseudotachylytes: 1. Thermal demagnetization experiments

et al. 2014

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Fault pseudotachylytes form by quenching of silicate liquids produced through coseismic frictional melting. Here we show that in natural pseudotachylytes the main carrier of magnetic remanence blocked in during cooling of the frictional melt is fine-grained magnetite. This confirms previous studies on friction melt experiments. Stoichiometric magnetite, produced during earthquakes by the breakdown of ferromagnesian silicates, records the ambient magnetic field during seismic slip. We find that most fault pseudotachylytes exposed in the Santa Rosa Mountains, southern California, a classic pseudotachylyte locality, acquired their natural remanent magnetization (NRM) upon cooling of the frictional melt through the range of magnetization blocking temperatures of the magnetite grains and this primarily constitutes a thermal remanent magnetization. NRM intensities typical of most pseudotachylyte veins range from 1 to 60·10 À4 Am 2 /kg. A few specimens, however, contain magnetizations significantly higher than that caused by the Earth's field as well as magnetization directions that are highly variable over short distances. Other magnetization processes, possibly related to coseismic electric currents, may be involved during the seismogenic process to control NRM acquisition.

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Rock magnetic expression of fluid infiltration in the Yingxiu‐Beichuan fault (Longmen Shan thrust belt, China)

Yang

Duan

et al. 2016

Geochem Geophys Geosyst

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Fluid infiltration within fault zones is an important process in earthquake rupture. Magnetic properties of fault rocks convey essential clues pertaining to physicochemical processes in fault zones. In 2011, two shallow holes (134 and 54 m depth, respectively) were drilled into the Yingxiu-Beichuan fault (Longmen Shan thrust belt, China), which accommodated most of the displacement of the 2008 Mw 7.9 Wenchuan earthquake. Fifty-eight drill core samples, including granitic host rock and various fault rocks, were analyzed rock-magnetically, mineralogically, and geochemically. The magnetic behavior of fault rocks appears to be dominated by paramagnetic clay minerals. Magnetite in trace amounts is identified as the predominant ferrimagnetic fraction in all samples, decreasing from the host rock, via fault breccia to (proto-)cataclasite. Significant mass-losses (10.7-45.6%) are determined for the latter two with the ''isocon'' method. Volatile contents and alteration products (i.e., chlorite) are enriched toward the fault core relative to the host rocks. These observations suggest that magnetite depletion occurred in these fault rocksexhumed from the shallow crust-plumbed by fluid-assisted processes. Chlorite, interpreted to result from hydrothermal activity, occurs throughout almost the entire fault core and shows high coefficients of determination (R 2 > 0.6) with both low and high-field magnetic susceptibility. Close relationships, with R 2 > 0.70, are also observed between both low and high-field magnetic susceptibility and the immobile elements (e.g., TiO 2 , P 2 O 5 , MnO), H 2 O 1 , and the calculated mass-losses of fault rocks. Hence, magnetic properties of fault rocks can serve as proxy indicators of fluid infiltration within shallow fault zones.

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Strong ferrimagnetic resonance signal and magnetic susceptibility of the Nojima pseudotachylyte in Japan and their implication for coseismic electromagnetic changes

Cited by 24 publications

References 47 publications

Magnetic properties of fault pseudotachylytes in granites

Magnetic properties of fault pseudotachylytes in granites

Coseismic magnetization of fault pseudotachylytes: 1. Thermal demagnetization experiments

Rock magnetic expression of fluid infiltration in the Yingxiu‐Beichuan fault (Longmen Shan thrust belt, China)

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