The effect of cooling rate on the intensity of weak‐field trm in single‐domain magnetite

Halgedahl, S. L.; Day, Richard L.; Fuller, M.

doi:10.1029/jb085ib07p03690

Cited by 178 publications

(176 citation statements)

References 6 publications

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“…Single domain (SD) theory predicts ∼3-7% change in magnetization per one order of magnitude change in cooling rate, with a slower cooling resulting in stronger magnetization (Dodson and McClelland-Brown, 1980;Halgedahl et al, 1980). This should correlate to the same amount of bias in paleointensity estimates.…”

Section: Introductionmentioning

confidence: 99%

“…The horizontal error bar indicates the plausible range of the cooling rate; see the text for a discussion). The dashed line represents the theoretical paleointensity overestimate (Halgedahl et al, 1980) with respect to the mean VDM calculated from the PINT data.…”

Section: Cooling Rate Effect On Plutonic Paleointensitymentioning

confidence: 99%

“…Using cooling rate estimates for oceanic gabbros (Gee and Meurer, 2002;Coogan et al, 2007), the formula given by Halgedahl et al (1980) for SD magnetite predicts that the cooling rate effect results in a 37-46% paleointensity overestimation in my samples. The present data are generally consistent with this prediction (Fig.…”

Section: Cooling Rate Effect On Plutonic Paleointensitymentioning

confidence: 99%

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Paleointensity estimates from oceanic gabbros: Effects of hydrothermal alteration and cooling rate

Usui

2013

Earth Planet Sp

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Gabbros recovered by previous ocean drillings were investigated in paleointensity and rock magnetic experiments. The young ages of the samples (ca. 0.78-1.3 Ma) enable a direct comparison between the plutonic paleointensity and volcanic data. Microscopic observations revealed two kinds of magnetite: needle-shaped exsolution in plagioclase and aggregate associated with the hydrothermal alteration of olivine. In Shaw paleointensity experiments, some samples revealed reasonable estimates, while some others showed an anomalously low ratio of natural remanent magnetization (NRM) versus thermoremanent magnetization (TRM). First-order reversal curve (FORC) diagrams indicated that the reasonable NRM/TRM were from non-interacting single domain magnetite exsolved in plagioclase, while the anomalously low NRM/TRM were from secondary magnetite associated with olivine. From the paleointensity results, the mean virtual axial dipole moment (VADM) was calculated to be 8.2 ± 2.1 10 22 Am 2 . Volcanic records in the PINT database for 0.78-1.3 Ma revealed a mean virtual dipole moment (VDM) of 6.3 ± 0.73 10 22 Am 2 . The difference between them is consistent with the theoretical prediction of the cooling rate effect on paleointensity. These results indicate that oceanic gabbros are reliable paleointensity recorders.

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Section: Introductionmentioning

confidence: 99%

Section: Cooling Rate Effect On Plutonic Paleointensitymentioning

confidence: 99%

Section: Cooling Rate Effect On Plutonic Paleointensitymentioning

confidence: 99%

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Paleointensity estimates from oceanic gabbros: Effects of hydrothermal alteration and cooling rate

Usui

2013

Earth Planet Sp

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“…Dodson and McClelland-Brown (1980) showed that blocking temperatures of single domain grains are related to the cooling rate and the TRM acquired at different cooling rates in the same field might differ significantly. This will bias the estimation of paleointensity (Halgedahl et al, 1980). In order to obtain the most accurate results, we applied a cooling rate correction for each specimen after the paleointensity experiment.…”

Section: Anisotropy Correctionmentioning

confidence: 99%

Geomagnetic intensity variations for the past 8 kyr: New archaeointensity results from Eastern China

Cai

Tauxe

Deng

et al. 2014

Earth and Planetary Science Letters

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In this study, we have carried out paleointensity experiments on 918 specimens spanning the last ∼7 kyr, including pottery fragments, baked clay and slag, collected from Shandong, Liaoning, Zhejiang and Hebei Provinces in China. Approximately half of the specimens yielded results that passed strict data selection criteria and give high-fidelity paleointensities. The virtual axial dipole moments (VADMs) of our sites range from ∼2 × 10 22 to ∼13 × 10 22 Am 2 . At ∼2250 BCE our results suggest a paleointensity low of ∼2 × 10 22 Am 2 , which increases to a high of ∼13 × 10 22 Am 2 by ∼1300 BCE. This rapid (less than 1000 yrs) six-fold change in the paleointensity may have important implications for the dynamics of core flow at this time. Our data from the last ∼3 kyr are generally in good agreement with the ARCH3k.1 model, but deviate significantly at certain time periods from the CALS3k.4 and CALS10k.1b model, which is likely due to differences in the data used to constrain these models. At ages older than ∼3 ka, where only the CALS10k.1b model is available for comparison, our data deviate significantly from the model. Combining our new results with the published data from China and Japan, we provide greatly improved constraints for the regional model of Eastern Asia. When comparing the variations of geomagnetic field in three global representative areas of Eastern Asia, the Middle East and Southern Europe, a common general trend of sinusoidal variations since ∼8 ka is shown, likely dominated by the dipole component. However, significant disparities are revealed as well, which we attribute to non-dipolar components caused by movement of magnetic flux patches at the core-mantle boundary.

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“…A remanence tensor for anisotropy corrections was calculated from TRMs acquired in six orthogonal positions, or with anhysteretic magnetizations acquired in nine positions. Corrections for cooling rate effects were done assuming a logarithmic relationship between TRM overestimation from ratios of laboratory versus original cooling rates (20), and cooling time from 500°C to 200°C approximations of 0.1 h, 3.7 h, and 6 h for the laboratory-fast, laboratoryslow, and ancient cooling times. In all experiments, the field during "in-field cooling" in the oven was 60 μT.…”

Section: Significancementioning

confidence: 99%

Six centuries of geomagnetic intensity variations recorded by royal Judean stamped jar handles

Ben‐Yosef

Millman

Shaar

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Earth's magnetic field, one of the most enigmatic physical phenomena of the planet, is constantly changing on various time scales, from decades to millennia and longer. The reconstruction of geomagnetic field behavior in periods predating direct observations with modern instrumentation is based on geological and archaeological materials and has the twin challenges of (i) the accuracy of ancient paleomagnetic estimates and (ii) the dating of the archaeological material. Here we address the latter by using a set of storage jar handles (fired clay) stamped by royal seals as part of the ancient administrative system in Judah (Jerusalem and its vicinity). The typology of the stamp impressions, which corresponds to changes in the political entities ruling this area, provides excellent age constraints for the firing event of these artifacts. Together with rigorous paleomagnetic experimental procedures, this study yielded an unparalleled record of the geomagnetic field intensity during the eighth to second centuries BCE. The new record constitutes a substantial advance in our knowledge of past geomagnetic field variations in the southern Levant. Although it demonstrates a relatively stable and gradually declining field during the sixth to second centuries BCE, the new record provides further support for a short interval of extreme high values during the late eighth century BCE. The rate of change during this "geomagnetic spike" [defined as virtual axial dipole moment > 160 ZAm 2 (10 21 Am 2 )] is further constrained by the new data, which indicate an extremely rapid weakening of the field (losing ∼27% of its strength over ca. 30 y).archaeomagnetism | archaeointensity | levantine archaeomagnetic curve | paleosecular variation | archaeomagnetic spikes R econstruction of geomagnetic secular variation during the Holocene has implications for various fields of research, from geophysics and other planetary sciences to biology and archaeology. Such reconstructions are based predominantly on heatimpacted geological and archaeological materials, whose thermal remanent magnetization (TRM) holds information on the geomagnetic field vector at the time of their last cooling. As evidence for fluctuating field behavior, including short (decadal) periods of rapid changes, is constantly growing (1-5), using records with excellent time resolution has become increasingly of interest.To improve the accuracy and precision of age constraints associated with estimates of ancient geomagnetic field strength, the current study exploits a set of archaeological artifacts whose ages are exceptionally well constrained. This set is composed of wellstudied ceramic jars from Judah/Yehud/Judea (Jerusalem and its vicinity), which bear royal stamp impressions on their handles (6-10). The stamped jars were part of the ancient administration of this region for about 600 y, between the late eighth and late second centuries BCE. As the types of stamp impressions changed with time according to the political situation, the jar handles provide an excellent recor...

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The effect of cooling rate on the intensity of weak‐field trm in single‐domain magnetite

Cited by 178 publications

References 6 publications

Paleointensity estimates from oceanic gabbros: Effects of hydrothermal alteration and cooling rate

Paleointensity estimates from oceanic gabbros: Effects of hydrothermal alteration and cooling rate

Geomagnetic intensity variations for the past 8 kyr: New archaeointensity results from Eastern China

Six centuries of geomagnetic intensity variations recorded by royal Judean stamped jar handles

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