Characteristics of magnetite in submarine basaltic glass

Pick, Thomas; Tauxe, Lisa

doi:10.1111/j.1365-246x.1994.tb00917.x

Cited by 66 publications

(49 citation statements)

References 33 publications

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“…Rock magnetic studies suggest that low-Ti single-domain titanomagnetite carries the remanent magnetization in these samples (Pick & Tauxe 1994). Furthermore, the remanence is acquired on time-scales comparable with laboratory cooling times.…”

Section: (C) Submarine Basaltic Glass Samplesmentioning

confidence: 89%

Long-term variations in palaeointensity

Selkin

Tauxe

2000

Philosophical Transactions of the Royal Society of London. Seri

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356

315

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We compile a dataset of reliable palaeointensity estimates based both on published work and on new data from basaltic glass. The basaltic glass data more than double the number of reliable (Thellier method with pTRM checks) palaeointensity estimates available. Although the new data dramatically improve both spatial and temporal coverage, there is still a strong bias toward the most recent past. The last 0.3 Ma claim over half of the data in our combined database. We therefore divide the data into two groups, the densely sampled last 0.3 Myr and the more sparsely sampled period of time comprising roughly half of the data from 0.3 to 300 Ma. Separating them in this way, it is clear that the dipole moment of the Earth over the past 0.3 Myr (ca. 8 10 22 A m 2 ) is dramatically higher than the average dipole moment over the preceding 300 Myr (ca. 5 10 22 A m 2 ). Inclusion of poor-quality results leads to an overestimate of the average dipole moment. Interestingly, no other signi cant changes in the distribution of dipole moments are evident over the 300 million year span of the data.

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Section: (C) Submarine Basaltic Glass Samplesmentioning

confidence: 89%

Long-term variations in palaeointensity

Selkin

Tauxe

2000

Philosophical Transactions of the Royal Society of London. Seri

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356

315

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“…Superparamagnetic behavior has been documented in otherwise fresh natural basaltic glasses (Pick and Tauxe 1994), and in Fe-rich basaltic glasses quenched in the laboratory (Bowles et al 2011) but is not generally considered to contribute to Möss-bauer spectra of laboratory-quenched glasses. Non-paramagnetic components of Mössbauer spectra, including broad absorptions approximately symmetric about CS = 0 mm/s as well as sextets, are a common feature in such glasses, in many cases comprising a larger fraction of the Fe than documented for VF3 or M544 .…”

Section: Superparamagnetism In Quenched Glassesmentioning

confidence: 98%

Accurate determination of Fe³⁺/∑Fe of andesitic glass by Mössbauer spectroscopy

Zhang

Sølheid

Lange

et al. 2015

American Mineralogist

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To evaluate the accuracy of Fe 3+ and Fe 2+ ratios in silicate glasses determined by Mössbauer spectroscopy, we examine in detail the temperature (47-293 K) of Mössbauer spectra for two andesitic glasses, one quenched at 1 atm, 1400 °C (VF3) and the other at 3.5 GPa, 1600 °C (M544). Variabletemperature Mössbauer spectra of these two glasses are used to characterize the recoilless fraction, f, by two different methods-a relative method (RM) based on the temperature dependence of the ratios of Fe 3+ and Fe 2+ Mössbauer doublets and the second based on the temperature dependence of the center shift (CS) of the doublets. The ratio of the recoilless fractions for Fe 3+ and Fe 2+ , C T , can then be used to adjust the observed area of the Mössbauer doublets into the Fe 3+ /SFe ratio in the sample. We also evaluated the contributions of non-paramagnetic components to the Fe in the glasses by determining the influence of applied magnetic field on sample magnetization. Finally, for the VF3 glass, we determined the Fe 3+ /SFe independently by wet chemical determination of the FeO content combined with careful electron microprobe analyses of total Fe. Recoilless fractions determined with the CS method (CSM) are significantly smaller than those determined with the relative method and suggest larger corrections to room-temperature Fe 3+ /SFe ratios. However, the RM determinations are believed to be more accurate because they depend less on the assumption of the Debye harmonic model and because they produce more nearly temperature-independent estimates of Fe 3+ /SFe ratios. Non-linear responses of sample magnetizations to applied magnetic fields indicate that the glasses contain a small (0.4-1.1% for VF3) superparamagnetic component that is most likely to be nanophase precipitates of (Fe,Mg)Fe 2 O 4 oxide, but corrections for this component have negligible influence on the total Fe 3+ /SFe determined for the glass. For the VF3 glass, the Fe 3+ /SFe produced by uncorrected room-temperature Mössbauer spectroscopy [0.685 ± 0.014 in two standard deviation (2s)] agrees within 3% of that determined by wet chemistry (0.666 ± 0.030 in 2s). The Fe 3+ /SFe corrected for recoilless fraction contributions is 0.634 ± 0.078(2s), which is 7.5% lower than the uncorrected room-temperature ratio, but also agrees within 5% of wet chemical ratio. At least for this andesitic glass, the room-temperature determination of Fe 3+ /SFe is accurate within analytical uncertainty, but room-temperature Mössbauer determinations of Fe 3+ /SFe are always systematically higher compared to recoilless-fraction corrected ratios.

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“…Many factors, including magnetic mineralogy, grain size, and so on, can affect hysteresis properties. Since a sensitive and less time-consuming magnetometer for measuring hysteresis properties became available (Flanders, 1988), it has been increasingly recognized that distorted hysteresis loops, such as potbellied (spreading at the middle of loops) or waspwaisted (constricted at the middle of loops), commonly occur in rocks and sediments (e.g., Jackson, 1990;Borradaile et al, 1993;Pick and Tauxe, 1994;Roberts et al, 1995). These distorted hysteresis loops originate from mixed assemblage of multiple magnetic components with different mineralogy or grain size.…”

Section: Introductionmentioning

confidence: 99%

Variable shape of magnetic hysteresis loops in the Chinese loess-paleosol sequence

Fukuma

Torii

2014

Earth Planet Sp

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Shape of magnetic hysteresis loops of the Chinese loess-paleosol sequence is variable with low-field susceptibility and is weakly constricted in samples with intermediate susceptibility (~1.0 × 10 -6 m 3 /kg). The analyses of the hysteresis loops show that both low-(ferrimagnetic) and high-coercivity (antiferromagnetic) components are present and the ferrimagnetic component dominate the magnetic characteristics. The ratio of ferrimagnetic over antiferromagnetic minerals (S ratio) and the superparamagnetic fraction increase with increasing susceptibility. Neither simple two-component mixtures of ferrimagnetic and antiferromagnetic minerals nor of single-domain and superparamagnetic grains fully explain the constricted hysteresis loops. We interpret the variation of the loop shape with susceptibility in the following way. When the ratio of the ferrimagnetic to antiferromagnetic contribution is relatively low (low susceptibility), the broad loop is controlled by lithogenic ferrimagnetic and antiferromagnetic minerals. For samples with intermediate susceptibility values, constricted shape originates from an addition of a broad loop from the lithogenic fraction and a narrow loop from a pedogenic fraction with high superparamagnetic content. Then with further susceptibility increase, the constricted shape almost disappears and the loop is dominated by the pedogenic fraction. The variation of hysteresis loop shape with susceptibility can be a useful indicator of the degree of pedogenesis for loess-paleosol samples.

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Characteristics of magnetite in submarine basaltic glass

Cited by 66 publications

References 33 publications

Long-term variations in palaeointensity

Long-term variations in palaeointensity

Accurate determination of Fe³⁺/∑Fe of andesitic glass by Mössbauer spectroscopy

Variable shape of magnetic hysteresis loops in the Chinese loess-paleosol sequence

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Characteristics of magnetite in submarine basaltic glass

Cited by 66 publications

References 33 publications

Long-term variations in palaeointensity

Long-term variations in palaeointensity

Accurate determination of Fe3+/∑Fe of andesitic glass by Mössbauer spectroscopy

Variable shape of magnetic hysteresis loops in the Chinese loess-paleosol sequence

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Accurate determination of Fe³⁺/∑Fe of andesitic glass by Mössbauer spectroscopy