Magnetic Susceptibility of Pyrrhotite: Grain Size, Field and Frequency Dependence

Worm, Horst-Ulrich; Clark, David; Dekkers, Mark J.

doi:10.1111/j.1365-246x.1993.tb01472.x

Cited by 85 publications

(65 citation statements)

References 25 publications

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“…6). Pyrrhotite is the main magnetic carrier in the shergottites ) and has been shown to display a magnetic susceptibility that is strongly dependent on grain size and frequency (Worm et al 1993).…”

Section: Frequency Dependence Of Magnetic Susceptibilitymentioning

confidence: 99%

Stony meteorite characterization by non‐destructive measurement of magnetic properties

Smith

Ernst

Samson

et al. 2006

Meteorit & Planetary Scien

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All appendix tables for this article are available online at http://meteoritics.org.Abstract-Four parameters of low-field magnetic susceptibility (bulk value, frequency dependence, degree of anisotropy, and ellipsoid shape) have been determined for 321 stony meteorites from the National Collection of Canada. These parameters provide a basis for rapid, non-destructive, and accurate meteorite classification as each meteorite class tends to have a distinct range of values.Chondrites show a clear trend of increasing bulk susceptibility from LL to L to H to E within the 3.6 to 5.6 logχ (in 10 −9 m 3 /kg) range, reflecting increasing Fe-Ni metal and Fe-Ni sulfide content. Achondrite values range in logχ from 2.4 to 4.7 and primitive achondrites from 4.2 to 5.7. Frequency dependence is observed, using 19,000 Hz and 825 Hz, with variations in strength among meteorite classes and individual specimen dependence ranging from 1-25.6%. Degrees of anisotropy range from 1 to 53% with both oblate and prolate ellipsoids present. The aubrite class is marked by high degrees of anisotropy, low bulk magnetic susceptibility, and prolate fabric. Camel Donga is set apart from other eucrites, marked by higher bulk susceptibility, degree of anisotropy, and magnitude of oblate ellipsoid shape. The Shergotty, Nakhla, and Chassigny (SNC) meteorites show subclass distinction using frequency dependence and Chassigny is set apart with a relatively strong oblate fabric. The presence of both strong oblate and prolate fabrics among and within meteorite classes of chondritic and achondritic material points to a complex, multi-mechanism origin for anisotropy, more so than previously thought, and likely dominated by impact processes in the later stages of stony parent body formation.

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Section: Frequency Dependence Of Magnetic Susceptibilitymentioning

confidence: 99%

Stony meteorite characterization by non‐destructive measurement of magnetic properties

Smith

Ernst

Samson

et al. 2006

Meteorit & Planetary Scien

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“…Other common minerals in nature, like titanomagnetite or pyrrhotite, show a dependence of initial susceptibility vs field with the amount of T i and the grain size, respectively (Jackson et al 1998;Worm et al 1993). In hematite, some authors have hypothesized that the non linear behaviour of susceptibility is related to measurements made in fields higher than the coercivity or outside the Rayleigh zone (Hrouda 2002).…”

Section: Ac Susceptibilitymentioning

confidence: 99%

“…minerals which display an initial field-dependent susceptibility. For example, pyrrhotite, whose field variation of susceptibility is controlled by grain size (Worm 1991;Worm et al 1993;de Wall & Worm 1993;Martín-Hernández et al 2008); titanomagnetite, whose variation of susceptibility is controlled by their T i content (Jackson et al 1998), or hematite, whose controlling factor of susceptibility behaviour is not well understood (Hrouda 2002(Hrouda , 2007Pokornỳ et al 2004). …”

Section: Introductionmentioning

confidence: 99%

Haematite natural crystals: non-linear initial susceptibility at low temperature

Guerrero-Suarez

Martín-Hernández

2016

Geophys. J. Int.

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SUMMARYSeveral works have reported that hematite has non-linear initial susceptibility at room temperature, like pyrrhotite or titanomagnetite, but there is no explanation for the observed behaviours yet. This study sets out to determine which physical property (grainsize, foreign cations content, domain walls displacements) controls the initial susceptibility. The performed measurements include microprobe analysis to determine magnetic phases different to hematite; initial susceptibility (300 K); hysteresis loops, SIRM and backfield curves at 77 K and 300 K to calculate magnetic parameters and minor loops at 77 K, to analyze initial susceptiblity and magnetization behaviours below Morin transition. The magnetic moment study at low temperatura is completed with measurements of Zero Field Cooled-Field Cooled (ZFC-FC) and AC-susceptibility in a range from 5 − 300 K. The minor loops show that the non-linearity of initial susceptibility is closely related to Barkhausen jumps. Because of initial magnetic susceptibility is controlled by domain structure it is difficult to establish a mathematical model to separate magnetic subfabrics in hematite-bearing rocks.

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“…We measured k over the range 400 to 40,000 A/m at 400 Hz and to 80,000 A/m at 800 Hz. Frequency dependence of k introduces issues of complex susceptibility, i.e., resistivity versus true susceptibility, and is discussed elsewhere especially with reference to sulphides minerals (BORRADAILE et al, 1992;JACKSON and WORM, 2001;MULLINS and TITE, 1973;WORM et al, 1993). However, in practical applications, for frequencies <20 kHz the out-of-phase resistivity component is sufficiently negligible in comparison with the in-phase susceptibility component and higher frequencies permit greater precision in measuring k.…”

Section: Susceptibility Measurement Conditions Especially Field-depementioning

confidence: 99%

Induced Magnetization of Magnetite-titanomagnetite in Alternating Fields Ranging from 400 A/m to 80,000 A/m; Low-field Susceptibility (100 – 400 A/m) and Beyond

Borradaile

Stupavsky²,

Metsaranta

2008

Pure appl. geophys.

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For remanence-bearing minerals (RBM) such as magnetite-titanomagnetite, susceptibility to induced magnetism (M) measured in alternating fields (H AC ) is field-dependent. However, for fields B 400 A/m, measured in an AC induction coil instrument (at 19,100 Hz), susceptibility k 0 = M/H AC is sufficiently linear to provide a reproducible rock (or mineral) magnetic characteristic and its anisotropy may be related to arrangements of minerals in rock, or for single mineral grains to their crystalline or shape anisotropy. For any remanence-bearing mineral at higher fields k HF (¼ M/H AC ) is not constant and the term susceptibility is not normally used. This study bridges the responses between traditional low-field susceptibility measurements and those due to high applied fields, for example when studying hysteresis or saturation magnetization of RBM. Where |k HF | is measured in alternating fields that peak significantly above 400 A/m the M(H AC ) relation is forced to follow a hysteresis loop in which |k HF | > k 0 for small |H AC | and where |k HF | decreases to zero for very large fields that achieve saturation magnetization. Hysteresis nonlinearity is due to remanence acquired with one field direction requiring a reverse field for its cancellation. We investigate the transition from initial, traditional ''lowfield'' susceptibility (k 0 ) measurements at 60 A/m, through 24 different fields from 400 A/m to 40,000 A/m (for very high k 0 to 80,000 A/m). This reveals M(H AC ) dependence beyond from conventional k 0 through the range of hysteresis behavior in fields equal to and exceeding that required to achieve saturation magnetization (M S ). We show k HF increases with peak H AC until the peak field is slightly less than saturation magnetization in natural rock samples rich in magnetite (TM 0 ¼ Fe 3 O 4 ) and TM 60 (Fe 2.4 Ti 0.6 O 4 ). All sample suites predominantly contain multidomain grains with subordinate pseudo-single domain and single-domain grains. k/k 0 increases by B 5% for fields up to 2 kA/m. Above 4 kA/m k/ k 0 increases steeply and peaks, usually between 24 kA/m and 30 kA/m where all grains magnetic moments are activated by H AC since this exceeds the coercive force of most grains. For higher peak H AC , k/k 0 declines sharply as increased H AC values more effectively flip M with each field-direction switch, leading to the low gradient at distal portions of the hysteresis loop. For M 0 -TM 60 bearing rocks, susceptibility peaks for fields *12 kA/m and for magnetite rich rocks up to 24 kA/m. These values are approximately 10% of saturation magnetizations (M S ) reported for the pure minerals from hysteresis DC field measurements. Both the field at peak k/k 0 and the peak k/k 0 value appear to be controlled by the dominant domain structure; multidomain behavior has larger k/k 0 peaks at lower H AC . Stacked k/k 0 versus H AC curves for each sample suite (n = 12 to n = 39) were successfully characterized at the 95% level by a polynomial fit that requires the cubic form k/k 0 = a + bH + cH 2 + dH 3 . Thu...

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Magnetic Susceptibility of Pyrrhotite: Grain Size, Field and Frequency Dependence

Cited by 85 publications

References 25 publications

Stony meteorite characterization by non‐destructive measurement of magnetic properties

Stony meteorite characterization by non‐destructive measurement of magnetic properties

Haematite natural crystals: non-linear initial susceptibility at low temperature

Induced Magnetization of Magnetite-titanomagnetite in Alternating Fields Ranging from 400 A/m to 80,000 A/m; Low-field Susceptibility (100 – 400 A/m) and Beyond

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