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Introductory notes on shock remanent magnetization and shock demagnetization of igneous rocks

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Summary

Effects of mechanical shocks of about 0.5 msec in duration on the remanent magnetization of igneous rocks are experimentally studied. The remanent magnetization acquired by applying a shock (S) in the presence of a magnetic field (H), which is symbolically expressed asJ R (H+S Ho), is very large compared with the ordinary isothermal remanent magnetization (IRM) acquired in the same magnetic field.J R (H+S Ho) is proportional to the piezo-remanent magnetization,J R (H+P+Po Ho).

The effect of applyingS in advance of an acquisition of IRM is represented symbolically byJ R (S H+ Ho).J R (S H+ Ho) can become much larger than the ordinary IRM, and is proportional to the advance effect of pressure on IRM,J R(P+ P0 H+ H0).

The effect of shockS applied on IRM in non-magnetic space is represented by the shock-demagnetization effect,J R(H+ H0 S), which also is proportional toJ R(H+ H0 P+ P0).

Because, the duration of a shock is very short, a single shock effect cannot achieve the final steady state. The effect ofn-time repeated shocks, is represented byJ 0+ΔJ *(n), whereJ 0 means the immediate effect and ΔJ *(n) represent the resultant effect of repeating, which is of mathematical expression proportional to [1−exp {−α(n−1)}].

Zusammenfassung

Die Effekte des mechanischen Stosses mit der Dauer von etwa 0.5 ms auf der remanenten Magnetisierung wurden experimentell nachgesucht. Das erworbene Remanenz der Magnetisierung nach dem Stoss (S) unter dem magnetischen Feld (H), das hier symbolisch alsJ R(H+ SH0) bezechnet wird, ist sehr stark im Vergleich mit der normalen isothermischen remanenten Magnetisierung (IRM) unter demselben magnetischen Feld.J R(H+ S H0) ist im Verhältnis zur piezoremanenten Magnetisierung,J R(H+ P+ P0 H0).

Der Effekt vom Stoss vor der Erwerbung von IRM wird symbolisch alsJ R(S H+ H0) bezeichnet.J R(S H+ H0) kann viel stärker als die normale IRM werden, im verhältnis zum Effekt des vorausgegebenen Drucks auf IRMJ R(P+ P0 H+ H0).

Der Effekt des Stosses auf IRM im Raum ohne magnetisches Feld wird mit dem Stossentmagnetisierungseffekt dargestellt,J R(H+ H0 S), der auch proportional zuJ R(H+ H0 P+ P0) ist.

Da die Dauer einzelnen Stosses sehr kurz ist, kann der Effekt des einmaligen Stosses den endgültigen stabilen Zustand nicht erreichen. Der Effekt nachn-maligen wiederholten Stossen wird alsJ 0+ΔJ *(n) bezeichnet, wobeiJ 0 den unverzüglichen Effekt bedeutet, und ΔJ *(n) beschreibt den resultanten Effekt der Stosswiederholung, dessen mathematische Darstellung proporational zu [1−exp {−α(n−1)}] ist.

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Authors and Affiliations

  1. Geophysics Research Laboratory, University of Tokyo, Tokyo, Japan

    Takesi Nagata

  2. Department of Earth and Planetary Science, University of Pittsburgh, Pittsburgh, USA

    Takesi Nagata

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  1. Takesi Nagata
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Nagata, T. Introductory notes on shock remanent magnetization and shock demagnetization of igneous rocks. PAGEOPH 89, 159–177 (1971). https://doi.org/10.1007/BF00875213

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  • DOI: https://doi.org/10.1007/BF00875213

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