Evidence of Single-Domain Magnetite in the Michikamau Anorthosite

1971 ◽  
Vol 8 (3) ◽  
pp. 361-370 ◽  
Author(s):  
G. S. Murthy ◽  
M. E. Evans ◽  
D. I. Gough
Keyword(s):  
Remanent Magnetization ◽  
Theoretical Models ◽  
Natural Remanent Magnetization ◽  
Single Domain ◽  
Isothermal Remanent Magnetization ◽  
Mineral Separation ◽  
Domain Configuration ◽  
Plagioclase Felspar ◽  
Magnetite Particles ◽  
Theoretical Evidence

The Michikamau anorthosite possesses very stable natural remanent magnetization, some of which resists alternating fields up to 1800 Oe. The rock contains two types of opaque grains, fine opaque needles of order 10 × 0.5 μ in the plagioclase felspar, and large equidimensional magnetite particles. Ore microscope studies suggest, but do not establish, that the needles are composed of magnetite. Saturation isothermal remanence and thermal demagnetization studies indicate magnetite as the carrier of remanent magnetization. In order to distinguish the effects of the large grains from those of the needles, mineral separation was used to show that an artificial specimen of essentially pure plagioclase had very similar isothermal remanent magnetization properties to the whole rock. Both indicated magnetite as the magnetic mineral. Thermoremanent properties of the separated mineral fractions indicated magnetite as the dominant magnetic constituent but showed some evidence of laboratory-produced hematite. Theoretical models of grains elongated along [111] and [110] axes are used to show that magnetite needles can exist in stable single-domain configuration in the size and shape ranges of the needles observed in the Michikamau anorthosite. There is thus considerable experimental and theoretical evidence for the conclusion that the stable remanent magnetization of the Michikamau anorthosite is carried by fine single–domain needles of magnetite in the plagioclase felspar.

Direct determination of the natural remanent magnetization effect in a hole drilled in layered ground from magnetic field and susceptibility logs

Geophysics ◽  
1992 ◽  
Vol 57 (7) ◽  
pp. 872-884 ◽  
Author(s):  
Guy Desvignes ◽  
Véronique Barthes ◽  
Alain Tabbagh
Keyword(s):  
Magnetic Field ◽  
Remanent Magnetization ◽  
Direct Determination ◽  
Theoretical Models ◽  
Natural Remanent Magnetization ◽  
Case Examples ◽  
Joint Interpretation ◽  
The Fourier Transform ◽  
Layered Ground

A new method as presented, allows the joint interpretation of both electromagnetic (EM) and magnetic logs in layered ground, based on the fact that the susceptibility responses for these two measurements are linear. Thus we can make use of the classical properties of the Fourier transform to extract from these two signals the magnetic field due to remanent magnetization. Theoretical models show that for a sufficient sample step this remanent magnetization can be recovered, even if the Koenigsberger ratio is of the order of 0.2 and if the thickness of the magnetized layer is of the order of 1 m. The results for two case examples in a sedimentary context are also shown. Despite the difficulties due to experimental procedures, we show that the amplitude of the extracted information is significant in these two cases, even if its variations are somewhat structureless and cannot be easily explained by the geology.

Magnetic characteristics of Luna 16 and 20 samples

1977 ◽  
Vol 284 (1319) ◽  
pp. 151-156 ◽  
Keyword(s):  
Grain Size ◽  
Iron Content ◽  
Remanent Magnetization ◽  
Natural Remanent Magnetization ◽  
Magnetic Behaviour ◽  
Heavy Fraction ◽  
Magnetic Characteristics ◽  
Iron Particles ◽  
Isothermal Remanent Magnetization ◽  
Rock Fragments

The natural remanent magnetization of rock fragments L2015,3,1 and L2015,3,11 was found to be < 3.5 x 10 -7 and < 40 x 10 -6 G cm 3 g -1 respectively. The former sample, from isothermal remanent magnetization (i.r.m.) measurements, contained very little iron, while the latter sample had a much higher iron content and exhibited i.r.m. characteristics similar to breccia samples from Apollo missions. Susceptibility and i.r.m. measurements have shown that Luna 16 fines contain about four times as much iron as Luna 20 samples and that the light fractions from the density separations contain about twice as much iron as the heavy fraction. Like the Apollo fines, the magnetic behaviour of Luna 16 and 20 fines is dominated by small iron particles, most of which are superparamagnetic and of grain size less than about 13 nm.

scholarly journals Application of the pseudo-Thellier technique to a paleomagnetic record from lake El Trébol (Patagonia, Argentina)

2008 ◽  
Vol 47 (4) ◽  
pp. 319-327
Author(s):  
C. S. G. Gogorza ◽  
S. Torcida ◽  
A. M. Sinito ◽  
M. A. E. Chaparro
Keyword(s):  
Magnetic Susceptibility ◽  
Error Estimates ◽  
Sediment Core ◽  
Standard Method ◽  
Remanent Magnetization ◽  
Reasonable Agreement ◽  
Natural Remanent Magnetization ◽  
Isothermal Remanent Magnetization ◽  
Low Field ◽  
Relative Paleointensity

The pseudo-Thellier technique was applied to obtain relative paleointensity determinations using a sediment core from Lake El Tre?bol (Patagonia, Argentina). Measurements of intensity of natural remanent magnetization left (NRMleft) after AF demagnetization versus intensity of anhysteric remanent magnetization gained (ARMgained) at the same peak were carried out on a set of samples. Two versions of a jackknife resampling scheme were used to get error estimates on the paleointensity. The pseudo-Thellier paleointensity records were compared with the authors previous results where the remanent magne- tization at 20mT (NRM20mT) has been normalized using the anhysteric remanent magnetization at 20mT (ARM20mT), the satu- ration of the isothermal remanent magnetization at 20mT (SIRM20mT) and the low field magnetic susceptibility (k) (Gogorza et al., 2006). The pseudo-Thellier record shows a reasonable agreement with the standard method of normalization (NRM20mT/ ARM20mT).

Preliminary absolute paleointensity estimation from a single volcanic-glass grain extracted from an unwelded pyroclastic flow

2020 ◽  
Author(s):  
Yuhji Yamamoto ◽  
Hiromi Takeda ◽  
Masahiko Sato ◽  
Hiroshi Kawabata
Keyword(s):  
Pyroclastic Flow ◽  
Remanent Magnetization ◽  
Volcanic Glass ◽  
Volcanic Eruptions ◽  
Natural Remanent Magnetization ◽  
Primary Component ◽  
Pyroclastic Flows ◽  
Isothermal Remanent Magnetization ◽  
Inflection Points ◽  
Stable Characteristic

&lt;p&gt;Many pyroclastic flows are distributed around Japan. They usually involve volcanic-glass grains. These grains are considered to form at the timing of volcanic eruptions and are expected to have magnetic inclusions consisting of tiny single (titano)magnetites with recording the paleomagnetic field. We have extracted single volcanic-glass grains of pumice-type with a diameter of 0.60-0.84 mm from an unwelded part of the Ito pyroclastic flow deposits (A-Ito, 26-29 ka; Machida and Arai, 2003), Kyusyu, Japan. A series of rock- and paleomagnetic measurements have been made on the grains.&lt;/p&gt;&lt;p&gt;Sixty-seven out of 88 grains had detectable intensities of natural remanent magnetization. Some of such grains were further investigated. Results of low-temperature magnetometry exhibited inflection points at 105-120 K, suggesting magnetite as a main remenence carrier. Stepwise alternating field demagnetization revealed an existence of stable characteristic remanence (ChRM) which was interpreted to be a primary component.&amp;#160;&lt;/p&gt;&lt;p&gt;Tsunakawa-Shaw method (Tsunakawa and Shaw, 1994; Yamamoto et al., 2003), one of the latest absolute paleointensity (API) techniques to date, was applied to selected grains having stable ChRMs. On the application we newly included measurements related to an isothermal remanent magnetization (IRM). Four successful results were obtained by an adoption of IRM corrections, giving an average API value of about 25 &amp;#956;T. This corresponds to a virtual axial dipole moment (VADM) of about 50 ZAm&lt;sup&gt;2&lt;/sup&gt;, which is consistent with the contemporaneous VADM of the sedimentary record (PISO-1500; Channell et al., 2009).&amp;#160;&lt;/p&gt;

Magnetic Properties of Coring Samples from Aceh Basin West Off Sumatera Island

2014 ◽  
Vol 896 ◽  
pp. 434-439
Author(s):  
Eddy Z. Gaffar
Keyword(s):  
Remanent Magnetization ◽  
Natural Remanent Magnetization ◽  
Magnetic Polarity ◽  
Isothermal Remanent Magnetization ◽  
Reverse Polarity ◽  
Geologic Time ◽  
The Third ◽  
Geologic Time Scale ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Three oriented core samples was taken by Japanese MIRAI Research Vessel in Aceh Basin west of the Sumatera Island. 927 small box samples from 3 coring samples was measure. Core bottom ages of three cores are in the last glacial maximum (around 19 kyBP). We measured Natural Remanent Magnetization (NRM), NRM after Alternating Field Demagnetization up to 800 Oe. Measurement of NRM have done by 2G Enterprice Squid, Isothermal Remanent Magnetization (IRM) and Anhysteretic Remanent Magnetization (ARM) on Paleomagnetic Laboratory of Geological Survey of Japan. Result of NRM after Alternating Field Demagnetization shows that there are reverse polarizaty magnetizations. This reverse polarity seems not usual since in Geologic Time Scale 1989 showed that the first reversal polarity was between Brunches Normal Epoch and Jaramillo Epoch beginning at 0.75 Ma There are some possibility of reverse polarity events contained in the three cores mentioned above. The first possibility is the result of the tsunami so that the sediment that settles on the Aceh Basin was a sediment that remain turbid flows that enable magnetic recording on magnetic sediment did not follow directions when he formed so that it seems a polarity reverse polarity when only superficial. The second possibility is indeed occurs under reverse polarity at age 700.000 years. Research in Argentina, South America show that between 11 thousand to two thousand years ago there was an excursion from the magnetic polarity produces some reverse polarity at the time (Nami, 1999). The third possibility was circular variation magnetic.

scholarly journals ARCHAEOMAGNETIC STUDIES IN KILNS FROM N. GREECE

2017 ◽  
Vol 43 (4) ◽  
pp. 1888 ◽  
Author(s):  
E. Aidona ◽  
D. Kondopoulou ◽  
M. Alexandrou ◽  
N. Ioannidis
Keyword(s):  
Magnetic Field ◽  
Remanent Magnetization ◽  
Natural Remanent Magnetization ◽  
Archaeological Sites ◽  
Isothermal Remanent Magnetization ◽  
Thermomagnetic Analysis ◽  
Intensity Measurements ◽  
Magnetic Carriers ◽  
Characteristic Component

Archaeomagnetism combines the magnetic properties of baked materials with Archaeology. The archaeomagnetic method can be applied to any kind of permanent - in situ or displaced- burnt structures, such as kilns, ovens, hearths, burnt floors, tiles, bricks and pottery fragments, the latter for intensity measurements only. In this study we present the latest archaeomagnetic results from archaeological sites which are distributed in N. Greece (Polymylos, Sani, Thesssaloniki). The Natural Remanent Magnetization (NRM) and the magnetic susceptibility of the samples have been initially measured. The samples have been subjected to magnetic cleaning (AF and Thermal demagnetizations) and this procedure revealed the characteristic component of the ancient magnetic field. Rock magnetic experiments such as acquisition of the Isothermal Remanent Magnetization (IRM) and thermomagnetic analysis have been performed in pilot samples in order to identify the main magnetic carriers. Finally the secular variation curves for Greece and the SCHA.DIF.3K model were used in order to date these archaeological structures. This dating improved or modified the estimated archaeological ages.

V. The remanent magnetization of unstable Keuper Marls

1957 ◽  
Vol 250 (974) ◽  
pp. 130-143 ◽  
Keyword(s):  
Geomagnetic Field ◽  
Remanent Magnetization ◽  
Laboratory Experiments ◽  
Natural Remanent Magnetization ◽  
Single Domain ◽  
Dipole Field ◽  
Main Field ◽  
Axial Dipole ◽  
Geocentric Axial Dipole ◽  
Three Components

Measurements of the directions and intensities of magnetization of Keuper Marls from Sidmouth are described. The natural remanent magnetization of these rocks is shown to be unstable in the geomagnetic field. Certain laboratory experiments are described which show the natural remanent magnetization to consist of three components, a primary component created on, or soon after, deposition, in the same direction as that of the natural remanent magnetization of Keuper Sandstones and Marls described by Clegg, Almond & Stubbs (1954); a secondary component in the direction of a geocentric axial dipole field in Britain acquired since the last reversal of the main field and a temporary component built up by the geomagnetic field between collection and measurement. The temporary and secondary components are believed to be isothermal remanent magnetizations and to be due to the red haematite cement. Application of Néel’s theory of the magnetization of small single-domain particles shows that haematite grains of less than 0·15 μ in diameter will be magnetically unstable. The temporary and secondary components of magnetization are explained in terms of Néel’s theory. A suggested test of stability is described.

scholarly journals Natural and Induced Magnetization in the Bobolink, Dolichonyx Oryzivorus (Aves: Icteridae)

1986 ◽  
Vol 125 (1) ◽  
pp. 49-56 ◽  
Author(s):  
Robert C. Beason ◽  
William J. Brennan
Keyword(s):  
Remanent Magnetization ◽  
Natural Remanent Magnetization ◽  
Single Domain ◽  
7 Tesla ◽  
Magnetic Characteristics ◽  
Passerculus Sandwichensis ◽  
Dolichonyx Oryzivorus ◽  
Savannah Sparrow ◽  
Histochemical Tests ◽  
The Relationship

The magnetic characteristics of the heads from 28 bobolinks [Icteridae: Dolichonyx oryzivorus (L.)] were analysed using remanence magnetometers. The natural remanent magnetization of 12 freshly preserved heads averaged 3.20xl0−7 electromagnetic units (e.m.u.) (l e.m.u. = 103Am−1) and was oriented horizontally from side to side. An electromagnet was used to induce magnetization with external field strengths of up to O.7 Tesla (T). The average saturation isothermal remanent magnetization (sIRM) for 23 bobolink heads was 2.49×10−5e.m.u. Because the IRM was attained partially below 0.1 T and totally below 0.3 T, we believe that the magnetic material in the bobolink is at least partially single domain magnetite. The relationship between the IRM acquisition and alternating field (a.f.) demagnetization curves indicates that the single or pseudo-single domain grains of magnetite interact. Similar results were obtained on one savannah sparrow (Emberizidae: Passerculus sandwichensis) head and one indigo bunting (Emberizidae: Passerine cyanea) head. When some bobolink heads were subdivided, most or all of the magnetization was concentrated in the area from the nasal cavity to the orbit. Light microscopy and histochemical tests confirm the localization of inorganic iron in this region.

Investigations of Some Magnetic and Mineralogical Properties of the Laschamp and Olby Flows, France

1971 ◽  
Vol 1 (4) ◽  
pp. 511-521 ◽  
Author(s):  
John Whitney ◽  
H. P. Johnson ◽  
Shaul Levi ◽  
Bernard W. Evans
Keyword(s):  
Magnetic Field ◽  
High Temperatures ◽  
Geomagnetic Field ◽  
Remanent Magnetization ◽  
Single Domain ◽  
Field Reversal ◽  
Ambient Magnetic Field ◽  
Mineralogical Properties ◽  
Magnetite Particles

Rock-magnetic, paleomagnetic and petrologic properties of samples from the Laschamp and Olby basalt formations in France were studied to aid in determining the validity of the Laschamp geomagnetic field reversal reported by Bonhommet and Babkine. The Laschamp flow contains ilmenomagnetite, with partial alteration of the magnetite to hematite. Ilmenomagnetite in the Olby flow has largely recrystallized at high temperatures to a composite mozaic intergrowth of pseudobrookite, titanohematite and magnesioferrite, with rare residual magnetite and lamellae of ilmenite. The remanent magnetization is stable and resides primarily in single-domain magnetite particles. Our results indicate that the magnetizations of the Laschamp and Olby flows faithfully record the direction of the ambient magnetic field in which they cooled.

Introduction of Fine Engineered Domain Configuration into Potassium Niobate Single Crystals

2007 ◽  
Vol 350 ◽  
pp. 89-92
Author(s):  
Keisuke Yokoh ◽  
Tomomitsu Muraishi ◽  
Song Min Nam ◽  
Hirofumi Kakemoto ◽  
Takaaki Tsurumi ◽  
...  
Keyword(s):  
Electric Field ◽  
Single Crystals ◽  
Room Temperature ◽  
Single Domain ◽  
Potassium Niobate ◽  
Field Exposure ◽  
Domain State ◽  
Domain Configuration ◽  
Dc Electric Field ◽  
Direction Of Polarization

To induce fine engineered domain configurations into potassium niobate (KNbO3) single crystals, two kinds of methods were performed, i.e., (1) high DC electric field exposure along the opposite direction of polarization of KNbO3 single-domain crystals at room temperature, and (2) introduction of randomly oriented fine domain configuration by heat treatment at 700 °C and then high DC electric field exposure along [001]c direction of KNbO3 multidomain crystals at room temperature. When the method (1) was performed, finally, the poled KNbO3 crystals became to single-domain state again through the formation of multidomain state. On the other hand, the KNbO3 multidomain crystals were obtained by using the method (2), and an enhancement of piezoelectric-related properties was observed.

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