scholarly journals Magnetic properties of rocks of the Kapuskasing uplift (Ontario, Canada) and origin of long-wavelength magnetic anomalies

2010 ◽  
Vol 183 (2) ◽  
pp. 645-658 ◽  
Author(s):  
David J. Dunlop ◽  
Özden Özdemir ◽  
Vincenzo Costanzo-Alvarez
Keyword(s):  
Magnetic Properties ◽  
Magnetic Anomalies ◽  
Long Wavelength

Magnetic anomalies, chemical and magnetic properties at wide temperature range (15–1000 K) in LiSrxFe5-xO8 (x = 0, 0.025, 0.05)

2021 ◽  
Vol 859 ◽  
pp. 158290
Author(s):  
S. Udhayakumar ◽  
G. Jagadish Kumar ◽  
E. Senthil Kumar ◽  
M. Navaneethan ◽  
K. Kamala Bharathi
Keyword(s):  
Magnetic Properties ◽  
Wide Temperature Range ◽  
Magnetic Anomalies ◽  
Temperature Range

The sub-surface shape of part of the Loch Ailsh Intrusion, Assynt, as deduced from magnetic anomalies across the contact, with a note on traverses across the Loch Borralan Complex

1965 ◽  
Vol 102 (1) ◽  
pp. 46-58 ◽  
Author(s):  
Ian Parsons
Keyword(s):  
Magnetic Properties ◽  
Magnetic Anomalies ◽  
Surface Shape ◽  
Large Magnitude ◽  
Southern Margin

AbstractLocal magnetic anomalies of large magnitude are found over the marginal ultrabasic rocks of the Loch Ailsh intrusion. An intrepretation of these anomalies based on the measured magnetic properties of the pyroxenites shows that they are not reconcilable with a low-angle structure as required by the hypothesis that the intrusion is a stratified laccolite, and suggests that they form a steeply dipping sheet at the syenite-limestone contact. Similar anomalies occur along the southern margin of the Loch Borralan complex, suggesting steeply dipping marginal ultrabasic rocks.

Interpretation of Long Wavelength Magnetic Anomalies

1981 ◽  
pp. 231-255 ◽  
Author(s):  
Paolo Gasparini ◽  
Marta S. M. Mantovani ◽  
Wladimir Shukowsky
Keyword(s):  
Magnetic Anomalies ◽  
Long Wavelength

The distribution of surface magnetization in the English River and Kenora subprovinces of the Archean shield in Manitoba and Ontario

1979 ◽  
Vol 16 (9) ◽  
pp. 1764-1777 ◽  
Author(s):  
D. H. Hall ◽  
R. L. Coles ◽  
J. M. Hall
Keyword(s):  
High Surface ◽  
Magnetic Anomalies ◽  
Ambient Temperatures ◽  
Long Wavelength ◽  
Red Lake ◽  
Surface Magnetization ◽  
The Vertical Distribution ◽  
Granite Suite ◽  
Opaque Minerals ◽  
Distribution Of Magnetization

Surface magnetizations (induced and remanent) have been measured from almost 600 oriented cores collected over an area of 50 000 km2 covering portions of the Kenora, English River, and Red Lake subprovinces of the western Archean shield, between latitudes 49 and 51 °and longitudes 93 and 96°. These surface magnetizations reflect major geological provinces in the area, and throw light on the vertical distribution of magnetization and on the associated long wavelength magnetic anomalies. A major belt of high surface magnetization lies over the granodiorite–granite suite in the southern part of the English River subprovince and a major belt of low magnetization over the metasedimentary gneiss belt in the northern part of the subprovince. Remanent magnetization is prevalent, but is very unstable, apparently due to viscous remanence, and subparallel to the present-day geomagnetic field. This fact is of importance because rocks of this type, if deeply buried and at ambient temperatures above surface values, may lead to rather large intensities of magnetization. The magnetization is almost entirely due to magnetite, and titanomagnetite is only rarely encountered. The prevalent opaque minerals are magnetite, ilmenite, pyrite, pyrrhotite, and hematite.

Joint inversion of gravity and magnetic anomalies of eastern Canada

1998 ◽  
Vol 35 (7) ◽  
pp. 832-853 ◽  
Author(s):  
Ying Zheng ◽  
Jafar Arkani-Hamed
Keyword(s):  
Surface Topography ◽  
Joint Inversion ◽  
Gravity Anomalies ◽  
Magnetic Anomalies ◽  
Eastern Canada ◽  
Entire Area ◽  
Long Wavelength ◽  
Degree Correlation ◽  
Crustal Model ◽  
Density Perturbations

The power spectra and degree correlation of the surface topography and free-air gravity anomalies of eastern Canada show that the gravity anomalies are subdivided into three parts. The short-wavelength components (30-170 km, shorter than 30 km are not well resolved) largely arise from density perturbations in the crust and to a lesser extent from the surface topography and Moho undulation, whereas the contribution of intracrustal sources to the intermediate-wavelength components (170-385 km) is comparable with that of the topography. The long-wavelength components (385-1536 km) are overcompensated at the Moho. We present a crustal model for the intermediate- and long-wavelength components which takes into account the surface topography, density perturbations in the crust, and Moho undulation with a certain degree of isostatic compensation. The general characteristics of this model resemble the crustal structure revealed from seismic measurements. The reduced-to-pole magnetic anomalies of eastern Canada show no pronounced correlation with the topography and with the vertical gradient of the gravity anomalies, suggesting that the source bodies are within the crust and Poisson's relationship does not hold over the entire area. Assuming that the magnetic anomalies arise from induced magnetization, lateral variations of magnetic susceptibility of the crust are determined while taking into account the effects of the surface topography and the Moho undulation of our crustal model. The intermediate- and long-wavelength components of the susceptibility contrasts delineate major collision zones as low-susceptibility regions. We interpret this in terms of thermal demagnetization of the high-magnetic crustal roots beneath the collision zones.

scholarly journals Magnetic Properties and Redox State of Impact Glasses: A Review and New Case Studies from Siberia

Geosciences ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 225
Author(s):  
Pierre Rochette ◽  
Natalia S. Bezaeva ◽  
Andrei Kosterov ◽  
Jérôme Gattacceca ◽  
Victor L. Masaitis ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Oxidation State ◽  
Redox State ◽  
Magnetic Anomalies ◽  
Formation Processes ◽  
X Ray ◽  
Ferromagnetic Component ◽  
High Velocity Impacts ◽  
Superparamagnetic State

High velocity impacts produce melts that solidify as ejected or in-situ glasses. We provide a review of their peculiar magnetic properties, as well as a new detailed study of four glasses from Siberia: El’gygytgyn, Popigai, urengoites, and South-Ural glass (on a total of 24 different craters or strewn-fields). Two types of behavior appear: 1) purely paramagnetic with ferromagnetic impurities at most of the order of 10 ppm; this corresponds to the five tektite strewn-fields (including the new one from Belize), urengoites, and Darwin glass. Oxidation state, based in particular on X-ray spectroscopy, is mostly restricted to Fe2+; 2) variable and up to strong ferromagnetic component, up to the 1 wt % range, mostly due to substituted magnetite often in superparamagnetic state. Accordingly, bulk oxidation state is intermediate between Fe2+ and Fe3+, although metallic iron, hematite, and pyrrhotite are sometimes encountered. Various applications of these magnetic properties are reviewed in the field of paleomagnetism, magnetic anomalies, recognition of glass origin, and formation processes.

Magnetic properties of unrusted steel drums from laboratory and field‐magnetic measurements

Geophysics ◽  
1996 ◽  
Vol 61 (5) ◽  
pp. 1325-1335 ◽  
Author(s):  
Dhananjay Ravat
Keyword(s):  
Magnetic Properties ◽  
Magnetic Measurements ◽  
Magnetic Anomalies ◽  
Point Of View ◽  
Small Samples ◽  
Environmental Investigation ◽  
Bulk Magnetization ◽  
Steel Drums ◽  
Study Laboratory ◽  
Better Than

Laboratory‐derived magnetic properties from samples of steel drums appear to be lower than bulk magnetic properties required to produce observed magnetic anomalies over the same drums. The origin of this discrepancy is perhaps in the shape demagnetization experienced by samples used in the laboratory study. Laboratory observations of magnetic susceptibility in different directions suggest that the demagnetization mechanism may have significantly attenuated the laboratory‐derived magnetization values from small samples of drums. Field observations and computer modeling indicate that even though the effect of demagnetization is important for drum‐shaped objects, demagnetization is less pronounced in the shape of the drum than in the samples cut for laboratory measurements. Therefore, laboratory‐derived magnetizations from samples of steel drums cannot be used to model magnetic anomalies of steel drums. If laboratory‐derived magnetizations were used to model steel drums, the models would underestimate the resulting magnetic anomalies considerably and, in turn, would overestimate the number of buried drums at an environmental investigation site. Apparent bulk magnetization values for unrusted vertically oriented 55 and 30 gallon drums have been calculated (i.e., the values corrected for the effect of shape demagnetization of the drums). These range from ∼90 to ∼125 SI units (∼7 to ∼10 cgs units) for volume susceptibility and from ∼325 to ∼2750 A/m (∼0.325 to [Formula: see text]) for remanent magnetization (based on eight 55 gallon and four 30 gallon drums). Further deviations in these values could arise from the type and thickness of the steel and variations in manufacturing conditions affecting magnetizations. From the point of view of modeling the drums, at most source‐to‐observation distances applicable to environmental investigations, the equivalent source method is able to approximate the observed anomalies of steel drums better than the 3-D modeling method. With two years of rusting, magnetic anomalies of some of the drums have reduced, while in other drums, they have slightly increased. The overall magnetic changes caused by rusting appear to be more complex than anticipated, at least in the initial phase of rusting.

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