Properties of partial thermoremanent magnetization in pseudosingle domain and multidomain magnetite grains

Щербакова, В. В.; Щербаков, В. П.; Heider, Franz

doi:10.1029/1999jb900235

Cited by 118 publications

(140 citation statements)

References 25 publications

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“…7(c)), suggesting that the mineralogical changes primarily affect coarse grains, which have a fairly small contribution to the NRM and TRM intensities, while the main carriers are composed of a mixture of SD-PSD grains which either are not sensitive to the thermal alteration or have already been altered in the natural environment at T > T c before or during the baking of the sediments by the overlying lava. This suggestion is supported as well by the results of the hysteresis parameters measurements (mean M rs /M s = 0.18, mean H cr /H c = 2.74 typical for PSD grain sizes) and by the pTRM tails of the thermomagnetic criterion (Shcherbakova et al, 2000;Shcherbakov et al, 2001). Indeed, as seen in Fig.…”

Section: Paravakar Sectionsupporting

confidence: 74%

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Rock magnetic and paleointensity results from Mesozoic baked contacts of Armenia

et al. 2009

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Samples were obtained from three baked contacts and one lava flow along the upper Turonian-lower Coniacian Tovuz section, two baked contacts along the upper Coniacian-lower Santonian Paravakar section in the northern part of Armenia, and three baked contacts along the Titonian-Valanginian Kafan section in southern Armenia. A total of 130 samples were studied. Updated mean paleomagnetic poles were calculated for the Upper Cretaceous Tovuz-Paravakar sections (65.6• N, 162.2 • E, A 95 = 4.3, paleolatitude = 27.0 ± 3.4• ) and the Upper JurassicLower Cretaceous Kafan section (61.7• N, 158.9• E, A 95 = 4.8• , paleolatitude = 24.7 ± 3.8 • ). Paleointensity determinations could be estimated from two of the upper Cretaceous and three of the Upper Jurassic-Lower Cretaceous baked contacts, corresponding to a 30% success rate. The mean virtual dipole moments obtained were low (1.7-5.5 × 10 22 A m 2 ), which is in agreement with data published by Solodovnikov (1981a, 1983) for the same sections (3.0-4.4 × 10 22 A m 2 ). Our results support the hypothesis of the Mesozoic Dipole Low, even though the overall data are widely dispersed.

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Section: Paravakar Sectionsupporting

confidence: 74%

“…The thermomagnetic criterion (Shcherbakova et al, 2000) was used at the same time. For that, a partial thermoremanent magnetization pTRM(T 1 , T 2 ) was imparted by cooling a specimen first from T c to T 1 in zero field, followed by its cooling in a field from T 1 to T 2 (T 1 > T 2 ).…”

Section: Rock Magnetic Propertiesmentioning

confidence: 99%

Rock magnetic and paleointensity results from Mesozoic baked contacts of Armenia

et al. 2009

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“…This property can be checked for instance by comparing two different kinds of pTRM: a pTRM a (T 1 , T 2 ) acquired when the upper temperature T 1 is reached by cooling from Curie Temperature (T c ), i.e., from above, and a pTRM b (T 1 , T 2 ) when T 1 is reached by heating from T room , i.e., from below (Vinogradov and Markov, 1989;Shcherbakova et al, 2000). If the pTRMs are independent of the thermal history of the rock sample, then…”

Section: The Paleointensity Methods and Its Limitationsmentioning

confidence: 99%

“…6, consists of a direct verification of the Thellier law of independence of pTRM, which implies that any pTRM(T 1 , T 2 ), with T 1 > T 2 , must be entirely destroyed when heated in a zero field strictly in the interval T 2 -T 1 . From an experimental study on synthetic powders of magnetite and hematite of various sizes, Shcherbakova et al (2000) defined the A parameter by…”

Section: Bol'shakov and Shcherbakova's Ptrm-tail Testmentioning

confidence: 99%

Controlled atmosphere vibrating thermo-magnetometer (CatVTM): a new device to optimize the absolute paleointensity determinations

2009

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The laboratory of paleomagnetism of Montpellier (France) has developed a new one-axis vibrating thermal magnetometer dedicated to the study of physical properties of natural rocks remanence. Among its key characteristics, this apparatus allows both measurement of the magnetization moment on the interval from room temperature to 700• C with a precision of 2 × 10 −9 A m 2 and acquisition of a total or a partial thermo-remanent magnetization using a steady field from −100 up to 100 μT. Another point that is worth noting is that one can apply a controlled atmosphere by means of argon flux to prevent oxidation of the studied sample during heating. We report here a technical description of this new instrument and review some specific applications in absolute paleointensity surveys.

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“…Partial TRM (pTRM) checks were made at every one or two temperature steps for all specimens while the pTRM-tail check (Shcherbakova et al, 2000;Riisager and Riisager, 2001) was conducted on one specimen (DX01-15-1). The heating and cooling were carried out in air in about two hours (hold time at maximum temperatures were 15-20 minutes) using TDS-1 (Natsuhara Giken) or MMTD-18 (Magnetic Measurements) electric furnaces.…”

Section: Thellier Methodsmentioning

confidence: 99%

Paleomagnetism of the Datong monogenetic volcanoes in China: paleodirection and paleointensity during the middle to early Brunhes Chron

et al. 2007

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Paleomagnetic measurements were conducted on Datong volcanic rocks from China, which are thought to have formed in the mid to early Brunhes Chron. Meaningful site-mean paleodirections were obtained from 21 sites which are considered to represent 17 independent cooling units. They give a mean VGP (virtual geomagnetic pole) position of (76.5• N, 7.9• E) with A 95 =7.7 • (N=17), which is statistically distinct from geographic north. This dataset also yields an ASD (angular standard deviation) of 17.2• around the mean VGP position. Because the paleodirections form two clusters, the samples may record the paleomagnetic field during two different short periods and therefore may not average out paleosecular variation. Paleointensity measurements were conducted using three different methods. The DHT and LTD-DHT Shaw methods, the Thellier method, and the microwave Thellier method were applied to 119, 29 and 73 specimens respectively, and they give 66, 16 and 12 successful results (success rates are 55, 55 and 16%). From the LTD-DHT Shaw dataset, eight acceptable site-mean paleointensities are obtained. They give an average VDM (virtual dipole moment) of 3.79±1.94×10 22 A m 2 . This is 56% lower than the average VDM of 5.91±1.74×10 22 A m 2 (N=14) calculated from the selected Thellier data from the latest paleointensity database using the same criteria. One possible reason for this difference might be systematic overestimations of paleointensities by the Thellier method on volcanic rocks.

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Properties of partial thermoremanent magnetization in pseudosingle domain and multidomain magnetite grains

Abstract: Abstract. An experimental study was carried out to investigate the thermal demagnetization properties of partial thermoremanent magnetization (pTRM) .

Cited by 118 publications

References 25 publications

Rock magnetic and paleointensity results from Mesozoic baked contacts of Armenia

Rock magnetic and paleointensity results from Mesozoic baked contacts of Armenia

Controlled atmosphere vibrating thermo-magnetometer (CatVTM): a new device to optimize the absolute paleointensity determinations

Paleomagnetism of the Datong monogenetic volcanoes in China: paleodirection and paleointensity during the middle to early Brunhes Chron

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