Magnetic Susceptibility of Magnetite under Hydrostatic Pressure, and Implications for Tectonomagnetism

Nulman, A. A.; Shapiro, V. A.; Maksimovskikh, S. I.; Ivanov, N. A.; Kim, Joon; Carmichael, R. Stephen

doi:10.1007/978-94-010-9825-0_13

Cited by 5 publications

(6 citation statements)

References 9 publications

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“…A comprehensive theory to explain the experimental observations is difficult, however, because the nature of the applied load, be it hydrostatic or uniaxial, and the domain state, composition, size and shape of the studied magnetic minerals, influence the results [ Kean et al , 1976; Martin and Noel , 1988]. For example, magnetization and susceptibility vary less, and are more reversible upon stress release, under hydrostatic loads than under uniaxial loads [ Martin and Noel , 1988; Nulman et al , 1978; Kapicka , 1990].…”

Section: Introductionmentioning

confidence: 99%

Novel high pressure magnetic measurements with application to magnetite

Gilder

LeGoff

Peyronneau

et al. 2002

Geophysical Research Letters

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We report a novel system designed to measure reversible magnetic susceptibility of micron‐sized samples under high pressures in a diamond anvil cell. We find that magnetite reversible hysteresis parameters vary <15% below 0.6 to 1.0 GPa, while at higher pressures significant increases occur in (1) bulk coercivity (Hc) and (2) the ratio of saturation remanent magnetization (Mrs) to saturation magnetization (Ms). The net effect of pressure is to displace magnetite toward a truer single domain state with both higher Mrs/Ms and Hc. Our data, together with the fact that magnetite Curie temperature increases with pressure, suggest that magnetite can account for geomagnetic anomalies related to some subduction zones and potentially to meteorite impact sites on Earth, as well as magnetic signatures observed on some planetary bodies like Mars.

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Section: Introductionmentioning

confidence: 99%

Novel high pressure magnetic measurements with application to magnetite

Gilder

LeGoff

Peyronneau

et al. 2002

Geophysical Research Letters

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“…where A X is the change in susceptibility, H is the applied field, A(NRM) is the change in the remnant and PRM is the acquired pressure remnant moment, Nulman et al (1978) consider the effects of hydrostatic pressure on the susceptibility of magnetite. Much more work has involved the effects of uniaxial stress on the component parts of (1).…”

Section: Stress-strain Effects On the Local Magnetic Fieldmentioning

confidence: 99%

The time-dependence of electromagnetic response functions

Beamish¹

1982

Geophysical Surveys

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Abstract. Dynamic processes within the Earth axe capable of modifying many of its physical properties. This review considers the modification of electrical resistivity mainly by time-changes in the stressfield experienced by crustal materials. Laboratory experiments indicate that certain rock types, whose resistivity is controlled by the volume and geometry of microcracks, can undergo large resistivity variations in response to the typical strain accumulation and release that accompanies major earthquakes. Electromagnetic response functions axe reviewed with regard to their ability to monitor timechanges of resistivity in active regions. Some examples of the different experimental techniques used to investigate precursory changes in response functions prior to earthquakes are noted. The problems and successes of the subsequent correlation and interpretation of the derived response as a function of time are then discussed. Only relatively few controlled and integrated studies of time-dependent electromagnetic response functions exist. Those which are available, however, emphasise that changing stress-differentials occurring before major earthquakes can be monitored using suitable electromagnetic techniques.

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“…Pressure due to hydrostatic loading at 30-40 km may be 1000 MPa or more, whereas differential stresses in the lower crust are generally less than 200 MPa (Fountain, 1989 There have been a variety of studies examining the changes in magnetic susceptibility and remanent magnetization as a function of uniaxial stress and occasionally for hydrostatic pressure. Experiments on the effect of hydrostatic pressure on magnetic susceptibility have given conflicting results (Nulman et al, 1978;Martin, 1980;Kapicka, 1990Kapicka, & 1992. It seems likely from these results that magnetic susceptibility at elevated pressure (0-250 MPa) will be within 10% of the susceptibility measured at room pressure.…”

Section: Introductionmentioning

confidence: 99%

“…Since the magnetic sources reside at depth they are at elevated pressure due to overlying rock units and tectonic forces. Experiments on the effect of hydrostatic pressure on magnetic susceptibility have given conflicting results (Nulman et al, 1978;Martin, 1980;Kapicka, 1990Kapicka, & 1992. Experiments on the effect of hydrostatic pressure on magnetic susceptibility have given conflicting results (Nulman et al, 1978;Martin, 1980;Kapicka, 1990Kapicka, & 1992.…”

Section: Introductionmentioning

confidence: 99%

Effect of hydrostatic pressure on viscous remanent magnetization in magnetite‐bearing specimens

Kelso

Banerjee

1995

Geophysical Research Letters

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Rocks at depth in the crust acquire a viscous (i.e., time‐dependent) magnetization under the pressure‐temperature conditions at which they reside. There have been numerous studies on the effect of temperature on viscous magnetization but little work has been performed on the effect of hydrostatic pressure. We have studied viscous remanent magnetization at 22°C in a 0.1 mT field at 0.1 and 100 MPa for natural and synthetic multidomain magnetite. The viscous remanent magnetization was found to increase nearly linearly with log(time) at both pressures. There was little change in the rate of viscous acquisition between 0.1 and 100 MPa over the multidomain grain size range studied. Thus for rocks buried at depth in the earth the enhancement of magnetic viscosity by thermal fluctuations will dominate over effects due to hydrostatic pressure.

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Magnetic Susceptibility of Magnetite under Hydrostatic Pressure, and Implications for Tectonomagnetism

Cited by 5 publications

References 9 publications

Novel high pressure magnetic measurements with application to magnetite

Novel high pressure magnetic measurements with application to magnetite

The time-dependence of electromagnetic response functions

Effect of hydrostatic pressure on viscous remanent magnetization in magnetite‐bearing specimens

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