Magnetic hysteresis properties of greigite (Fe3S4) and a new occurrence in Holocene sediments from Swedish Lappland

Snowball, Ian

doi:10.1016/0031-9201(91)90004-2

Cited by 190 publications

(142 citation statements)

References 24 publications

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“…We therefore tested the measured crystal dimensions against calculations for both shape types. We also used values of shape, size, and coercivity of needle-like grains of greigite reported recently by Snowball [ 1991] for adjusting the diagram to experimental data. The latter was also used as the main criterion to determine whether the coercivity of greigite is dominated by shape or magnetocrystalline anisotropy.…”

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confidence: 99%

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Magnetic domain state and coercivity predictions for biogenic greigite (Fe₃S₄): A comparison of theory with magnetosome observations

Ricci¹,

Kirschvink²

1992

J. Geophys. Res.

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The discovery of bacteria that precipitate greigite within intracellular organelles (magnetosomes) offers new evidence about the origin of greigite in natural environments. Unlike magnetite, only scarce information is available abo~t the. magnetic challl~ristics of greigite. For this reason, and the present inability to grow these microorg~~s ~ pure ~re, It u ~ot known .whether ~r not the magnetosomes in the newly discovered greigiteprea~tatmg bactena ~re of smgle-d~ (SD) sJZe, as are the magnetosomes from magnetite-precipitating bactena. The hypotheSls of natural selection for magnetotactic behavior predicts that the greigite-bearing magnetos~es should also be s~~e magnetic domains. Using previously reported magnetic properties and crystalloglllphic featul7s for gre1g1te, we have calculated the size and shape boundaries expected for SD and superpa~gnetlc (SP~ behavior~ this m!neral. For further characterization ofthe greigite crystals, we analyzed the ~am state at vanous length/Width ratios assuming crystal shapes of parallelepipeds and prolate spheroids. Mag~etlte was used as control for the current theories supporting these calculations. We also present a simple alg~~thm to cal~te the upper size ~t of single-domain glllins. Our resuhs show that the crystals of bacterial greigite characte~ so far are l~ted m the region close to the single-domain superparamagnetic boundary and should have relatlv_ely lo~ .coerCJ.Vlty. If these crystals contribute to the magnetization ci sediments, remanence ~rodu~ by bacterial gre1g1te could be mistaken for large, multidomain magnetite in alternating field demagnetization studies.

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confidence: 99%

“…From (14) we calculate the wall widths when the minimum length is established for various q, and the minima lengths are recalculated with (13) [Snowball, 1991]. The square b…”

mentioning

confidence: 99%

Magnetic domain state and coercivity predictions for biogenic greigite (Fe₃S₄): A comparison of theory with magnetosome observations

Ricci¹,

Kirschvink²

1992

J. Geophys. Res.

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“…However, the samples analyzed display distinctly lower coercivities (H c <23 mT; Fig. 2) than has been reported for natural sedimentary greigites (H c = 41-57 mT; Snowball, 1991). In additional, the low IRM/K ratios of the samples (Fig.…”

Section: Discussionmentioning

confidence: 64%

Rock-Magnetic Properties of Pleistocene Passive Margin sediments: Environmental Change and Diagenesis offshore New Jersey

Urbat¹

1996

Proceedings of the Ocean Drilling Program, 150 Scientific Results

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Downhole changes in the concentration, grain size, and mineralogy of the magnetic components of Holocene through upper Pleistocene continental slope sediments (Ocean Drilling Program Holes 903A and 904A) were analyzed to judge the primary detrital vs. the diagenetic origin of the magnetic signal. Natural remanent magnetization (NRM), magnetic susceptibility (K), anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM), and additional hysteresis measurements were performed for densely sampled intervals (ca. every 15 cm). Single-domain through small pseudosingle-domain magnetite is identified as the dominant remanence carrying mineral. However, relative changes of the rock-magnetic properties on a sample-by-sample basis appear to be more instructive in detecting diagenetic overprints of the signal than are determinations of absolute grain sizes. Major downhole changes in the rock-magnetic properties are dominated by the original detrital signal and clearly record differences of glacial and interglacial modes of deposition. Postdepositional dissolution and the authigenic growth of magnetite modulate the detrital magnetic mineralogy dominantly in well-defined sections, which represent the contact of unconformably deposited sediment packages. This diagenetic alteration of the magnetic signal is restricted to the finer ferrimagnetic fraction and can be detected by analyzing the grain selectivity of the ARM acquisition process. The alteration of the magnetic mineralogy occurred repeatedly during sediment diagenesis.

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“…It is an indicator of magnetic grain size if only one magnetic mineral is present in a sample. It has also been used to indicate the presence of minerals other than magnetite in the sample, such as magnetic iron sulphides, which often occur in a SD state in sediments (e.g., Snowball, 1991;Roberts, 1995).…”

Section: Inter-parametric Ratiosmentioning

confidence: 99%

How does Chinese loess become magnetized?

Zhao

Roberts

2010

Earth and Planetary Science Letters

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Thick loess deposits on the Chinese Loess Plateau provide an outstanding archive of paleoclimate, geomagnetic field and paleoenvironmental changes over at least the last 2.6 Ma. Much work on magnetic polarity reversals, pedogenic magnetic enhancement and climatic change has been carried out over the past 30 years. However, questions about how Chinese loess becomes magnetized remain unanswered. In this thesis, I have sought to address key questions concerning magnetization processes in the Chinese loess. To understand magnetization processes, it is important to understand which magnetic minerals are present and the processes that caused them to be present. Magnetic and other analyses of both loess and paleosol samples indicate that pedogenic superparamagnetic and single domain magnetite and hematite can be present. The mass concentration of hematite can exceed 90% of the magnetic particle assemblage. An eolian dust deposition simulator designed for laboratory redeposition experiments was then used to demonstrate that both a depositional remanent magnetization (DRM) and a post-depositional remanent magnetization (PDRM) can be acquired by Chinese loess. Water content significantly affects the efficiency of PDRM acquisition. No significant PDRM was observed when the water content was below a critical threshold of 40%. Published paleomagnetic data from the Chinese loess indicate the widespread occurrence of inclination error. Detailed paleomagnetic studies of U-channel samples from the last loess/paleosol sequence at Yuanbao were made to assess whether the Chinese loess can accurately record geomagnetic relative paleointensity variations. Three normalized remanence records were determined using conventional normalization as well as the pseudo-Thellier method. Strong coherence among the normalized remanence records indicate that the whole range of magnetic minerals has been affected by pedogenesis. Poor similarity among published normalized remanence records from the Chinese loess, as well as with marine relative paleointensity records indicate that the Chinese loess is not suitable for relative paleointensity determinations. The range of magnetic minerals present and their varying distribution within loess and paleosol sediments indicate that the magnetization is due to a mixture of remanence acquisition mechanisms including DRM, PDRM, chemical remanent magnetization (CRM) and viscous remanent magnetizations, which also indicates complexities in remanence acquisition that will complicate attempts to extract relative paleointensity information. This thesis has provided an improved understanding of the mechanisms of Chinese loess magnetization, and re-emphasizes the importance of pedogenic CRM acquisition.

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Magnetic hysteresis properties of greigite (Fe3S4) and a new occurrence in Holocene sediments from Swedish Lappland

Cited by 190 publications

References 24 publications

Magnetic domain state and coercivity predictions for biogenic greigite (Fe₃S₄): A comparison of theory with magnetosome observations

Magnetic domain state and coercivity predictions for biogenic greigite (Fe₃S₄): A comparison of theory with magnetosome observations

Rock-Magnetic Properties of Pleistocene Passive Margin sediments: Environmental Change and Diagenesis offshore New Jersey

How does Chinese loess become magnetized?

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Magnetic hysteresis properties of greigite (Fe3S4) and a new occurrence in Holocene sediments from Swedish Lappland

Cited by 190 publications

References 24 publications

Magnetic domain state and coercivity predictions for biogenic greigite (Fe3S4): A comparison of theory with magnetosome observations

Magnetic domain state and coercivity predictions for biogenic greigite (Fe3S4): A comparison of theory with magnetosome observations

Rock-Magnetic Properties of Pleistocene Passive Margin sediments: Environmental Change and Diagenesis offshore New Jersey

How does Chinese loess become magnetized?

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Magnetic domain state and coercivity predictions for biogenic greigite (Fe₃S₄): A comparison of theory with magnetosome observations

Magnetic domain state and coercivity predictions for biogenic greigite (Fe₃S₄): A comparison of theory with magnetosome observations