Paleomagnetism of the 1180 Ma Grenvillian Umfraville gabbro, Ontario

1978 ◽  
Vol 15 (6) ◽  
pp. 956-962 ◽  
Author(s):  
D. T. A. Symons
Keyword(s):  
Remanent Magnetization ◽  
Pole Position ◽  
Paleomagnetic Data ◽  
Grenville Province ◽  
Thermal Demagnetization ◽  
Before And After ◽  
Primary Origin

The 1180 ± 20 Ma Umfraville gabbro is a slightly metamorphosed stock in the Grenville Province. It was sampled at 17 sites (183 specimens). After alternating field and thermal demagnetization the gabbro retains the same very stable remanent magnetization of primary origin both before and after screening. The screened AF direction from 10 sites (96 specimens) gives a pole position of 166°E, 11°S (δp = 7°, δm = 10°). This position is ≈ 13° southeast of that originally reported for the gabbro by Hood. This pole position either does not fit or necessitates modifications to the four hypotheses that have been invoked to explain Grenville paleomagnetic data.

New paleomagnetic data for the Triassic Guichon batholith of south-central British Columbia and their bearing on Terrane I tectonics

1983 ◽  
Vol 20 (8) ◽  
pp. 1340-1344 ◽  
Author(s):  
D. T. A. Symons
Keyword(s):  
British Columbia ◽  
Late Cretaceous ◽  
Vertical Axis ◽  
Pole Position ◽  
Primary Component ◽  
Paleomagnetic Data ◽  
Clockwise Rotation ◽  
North American Cordillera ◽  
Thermal Demagnetization ◽  
South Central

The 198 Ma Guichon batholith outcrops in the southern end of the Intermontane Belt or composite Terrane I of the western North American Cordillera. Thermal demagnetization of specimens from 19 sites at 200, 450, and 560 °C isolates a stable primary component at 560 °C in 13 sites, giving a pole position of 347°W, 52°N (δp = 5°, δm = 9°). These data support earlier results obtained by the author that indicate the batholith has undergone a clockwise rotation about a vertical axis of ~43 ± 7°. They also show that the batholith has undergone northward motion of 13 ± 6°, which supports recent arguments that the terrane underwent 14 ± 2° of northward translation between Late Cretaceous and pre-Miocene time.

Paleomagnetism of the Callander Complex and the Cambrian apparent polar wander path for North America

1991 ◽  
Vol 28 (3) ◽  
pp. 355-363 ◽  
Author(s):  
D. T. A. Symons ◽  
A. D. Chiasson
Keyword(s):  
Remanent Magnetization ◽  
Pole Position ◽  
Canadian Shield ◽  
Complete Spectrum ◽  
Isothermal Remanent Magnetization ◽  
Alkaline Complex ◽  
Grenville Province ◽  
Polar Wander ◽  
The Core ◽  
Apparent Polar Wander Path

The 7 km2 circular Callander alkaline complex was emplaced into anorthositic and granitic gneisses of the Grenville Province in the Canadian Shield about 575 ± 5 Ma ago at the start of the Cambrian. The complex has not been subsequently metamorphosed or tilted. Detailed alternating-field and thermal step demagnetization of 252 specimens from 29 sites led to the identification of a characteristic A magnetization component with a direction of D = 82.2°, I = 82.7° (α95 = 3.1°, k = 83, N = 26 sites) in 5 sites of mesocratic to leucocratic syenite from the core of the complex, in 5 sites of fenitized host rock from its aureole, and in 16 sites of lamprophyre from radiating dikes. Isothermal remanent-magnetization tests show that the A component is retained by both magnetite and hematite in a complete spectrum of domain sizes. A reversals test suggests and a contact test shows the A component to be primary. Its pole position at 46.3°S, 121.4°E(dp = 5.9°, dm = 6.1°) does not fall on published but poorly defined Cambrian apparent polar wander paths, leading to speculation on an alternative Cambrian path.

scholarly journals Tracing of traffic-related pollution using magnetic properties of topsoils in Daejeon, Korea

2020 ◽  
Vol 79 (20) ◽  
Author(s):  
Seungwoo Lee ◽  
Seoyeon Kim ◽  
Hyeji Kim ◽  
Youlee Seo ◽  
Yeoncheol Ha ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Susceptibility ◽  
Remanent Magnetization ◽  
Coarse Grained ◽  
Morphological Observation ◽  
Exhaust Emission ◽  
Thermal Demagnetization ◽  
Main Street ◽  
Traffic Related Pollution ◽  
The Difference

Abstract The present study was designed to explore the possibility of roadside pollution screening using magnetic properties of topsoil samples in Daejeon, South Korea. Low-field magnetic susceptibility, frequency dependence of magnetic susceptibility, susceptibility of anhysteretic remanent magnetization, isothermal remanent magnetization (IRM) acquisition and demagnetization, back-field IRM treatment, and thermal demagnetization of composite IRM were determined for roadside topsoil samples. Magnetic susceptibility measured on 238 samples from the upper 5 cm of the topsoils ranged from 8.6 to 82.5 × 10–5 SI with a mean of 28.3 ± 10.8 × 10–5 SI. The proximal zone, 55 m wide area situated on either side of the main street, exhibited an enhancement of magnetic susceptibility. In areas distant from the main street, low magnetic susceptibility (< 50 × 10–5 SI) was observed. The topsoil samples exhibited significant susceptibility contrasts, suggesting that two dimensional magnetic mapping was effective in identifying traffic-related pollution. A few magnetic hotspots with intensities of magnetic susceptibility near or over 50 × 10–5 SI might reflect the difference in topographic elevation and surface morphology. Among various IRM-related parameters, remanence of coercivity was most significant statistically. In most samples, IRM component analysis provided dual coercivity components. Thermal demagnetization of composite IRM and morphological observation of magnetic separates suggest angular magnetite produced by vehicle non-exhaust emissions spherical magnetite derived from exhaust emission to be the dominant contributors to the magnetic signal. It is likely that lower- and higher-coercivity components represent the presence of coarse-grained angular magnetite and fine-grained spherical magnetite, respectively.

Palaeomagnetic dating of hydrothermal alteration in the Woodford Shale, Oklahoma, USA

2019 ◽  
Vol 156 (12) ◽  
pp. 2043-2052
Author(s):  
Jennifer Roberts ◽  
Gerhard Heij ◽  
R. Douglas Elmore
Keyword(s):  
Hydrothermal Alteration ◽  
Remanent Magnetization ◽  
Vitrinite Reflectance ◽  
Pole Position ◽  
Potassium Feldspar ◽  
Hydrothermal Fluids ◽  
Late Permian ◽  
Ouachita Mountains ◽  
Woodford Shale ◽  
Southern Oklahoma

AbstractAn oriented Woodford Shale core from the eastern Ardmore Basin was sampled to test if the shale was an open or closed system to hydrothermal fluids, and to determine the timing of alteration. Mineralized fractures are ubiquitous in the core, and the shale exhibits a complex paragenesis with multiple hydrothermal minerals, including biotite, magnesite, norsethite, gorceixite and potassium feldspar present in and around the fractures. These minerals suggest that the Woodford Shale was an open system during part of its diagenetic history. Vitrinite reflectance (Ro) measurements indicate values of ∼1.81 % (∼230 °C). Palaeomagnetic analysis reveals a characteristic remanent magnetization (ChRM) with south-southeasterly declinations and shallow inclinations that resides in magnetite. This ChRM is interpreted to be either a chemical remanent magnetization (CRM) or a thermochemical remanent magnetization (TCRM) that was acquired at 245 ± 10 Ma during Late Permian time based on the pole position (51.0° N, 115.6° E). Because the palaeomagnetic specimens show evidence of extensive hydrothermal alteration, the CRM/TCRM is interpreted to date the migration of hydrothermal fluids through the shale. The agreement in timing with other studies that report hydrothermal alteration in southern Oklahoma and the Ouachita Mountains in Late Permian time, suggest that there were post-collisional fluid-flow events which accessed reservoirs of warm fluids.

Paleomagnetism of drill cores from Labrador offshore wells

1982 ◽  
Vol 19 (11) ◽  
pp. 2210-2214
Author(s):  
Raymund R. Pätzold ◽  
Ernst R. Deutsch
Keyword(s):  
Thermal Treatment ◽  
Early Cretaceous ◽  
Pole Position ◽  
Magnetic Intensity ◽  
Thermal Demagnetization ◽  
Initial Susceptibility ◽  
Normal Polarity ◽  
Short Core ◽  
Basaltic Material ◽  
Drill Cores

Values of the remanent magnetic intensity and inclination, initial susceptibility, and Koenigsberger ratios were obtained from basaltic material in four short core sections from three wells (Bjarni H81, two sections; Leif M48; Herjolf M92) drilled off Labrador. Published K–Ar dates are latest Jurassic to Early Cretaceous. Alternating-field (AF) demagnetization to 600 Oe (60 mT) and thermal demagnetization to 400 °C yielded stable, comparable remanent inclinations mostly of normal polarity for the Bjarni and Leif samples and revealed a change from reversed to normal polarity in the Bjarni well. Virtual pole position loci calculated from the paleoinclinations after AF and thermal treatment agree with published Early Cretaceous pole positions in the case of one Bjarni core, but the fit is poorer in the case of the second Bjarni core and the Leif core. These are the first paleomagnetic results from offshore Labrador.

Paleomagnetism of the Great Slave Supergroup, Northwest Territories, Canada: the Tochatwi Formation

1976 ◽  
Vol 13 (4) ◽  
pp. 555-562 ◽  
Author(s):  
M. E. Evans ◽  
D. K. Bingham
Keyword(s):  
Northwest Territories ◽  
North American ◽  
Pole Position ◽  
The Other ◽  
Thermal Demagnetization ◽  
Fine Grained ◽  
I 11 ◽  
Two Phases ◽  
Geological Work ◽  
Magnetic Vectors

The Tochatwi Formation comprises some 800 m of fine-grained red to buff sandstone in the upper part of the Great Slave Supergroup. Recent geological work indicates an age of 1700 m.y., but this is not yet known with certainty. Results from 29 sampling sites stratigraphically covering the Tochatwi Formation are presented. Standard paleomagnetic techniques indicate that post-folding remagnetization is common, and this is confirmed by analysis of the magnetic vectors removed as partial thermal demagnetization proceeds. Two phases of remagnetization are recognized, one of which can be attributed to nearby Mackenzie-age intrusions. The other phase is equivalent to a remagnetization observed by other workers in Kahochella Group strata at localities 70 km away. As yet, the source of this remagnetization event cannot be identified. Eight sampling sites have escaped total remagnetization and an earlier, pre-folding remanence has been isolated from these (D = 030, I = −11, k = 14, α95 = 15°). The corresponding pole position (144W, 18S) is remote from those deduced from North American rocks of similar age, and possible explanations of this problem are discussed.

Age of the Firesand River carbonatite complex from paleomagnetism

1989 ◽  
Vol 26 (11) ◽  
pp. 2401-2405 ◽  
Author(s):  
D. T. A. Symons
Keyword(s):  
Remanent Magnetization ◽  
Pole Position ◽  
Blocking Temperature ◽  
Isothermal Remanent Magnetization ◽  
Carbonatite Complex ◽  
Polar Wander ◽  
Partial Contact ◽  
Apparent Polar Wander Path ◽  
Temperature Spectra ◽  
Middle Proterozoic

The 2.3 km diameter Firesand River complex intrudes Archean volcanics and granites of the Wawa Subprovince in the Superior Province about 8 km east of Wawa, Ontario. It has given differing Middle Proterozoic K–Ar biotite ages of 1018 ± 50 and 1097 Ma. Alternating-field and thermal step demagnetization of specimens from three calcific carbonatite sites, five ferruginous dolomitic carbonatite sites, and one lamprophyre dike site isolated a stable mean direction of 290°, 33 °(α95 = 12°). Isothermal remanent magnetization tests indicate the remanence is held by single-to pseudosingle-domain magnetite and hematite in the carbonatite. The dike remanence is Keweenawan in age, thereby confirming its genetic relationship to the complex, and it gives a positive partial contact test with its host rock, indicating no postintrusive remagnetization. The blocking-temperature spectra indicate that postintrusive uplift has not exceeded about 4 km. The pole position for the complex is 183°E, 27°N (dp = 8°, dm = 13°). This pole lies directly on the well-dated Keweenawan apparent polar wander path, giving an age of 1090 ± 10 Ma, in agreement with the older K–Ar age. It also confirms geologic and aeromagnetic evidence that the complex has not been tectonically tilted since emplacement.

Additional Paleomagnetic Data on the Baffin Diabase Dikes and a Revised Franklin Pole

1973 ◽  
Vol 10 (4) ◽  
pp. 576-581 ◽  
Author(s):  
W. F. Fahrig ◽  
E. J. Schwarz
Keyword(s):  
Coastal Area ◽  
Remanent Magnetization ◽  
Magnetic Mineral ◽  
Paleomagnetic Data ◽  
Published Data ◽  
Baffin Island ◽  
Thermomagnetic Curves ◽  
Representative Material

Paleomagnetic data were obtained from eleven additional sites on Baffin diabase dike intrusions (part of the Franklin diabases). The rock at four sites was found to be normally magnetized, at six sites reversely magnetized, and at one site the rock contained no primary remanent magnetization that could be isolated by alternating field (a.f.) demagnetization. Baffin Island is divisible into several zones within which the Baffin dikes are either normally or reversely magnetized. This may indicate that more than one reversal is represented. The ten sites yield a pole at 168 °E, 6 °N, α95 = 5°, and when combined with previously published data (total 46 sites) yield a revised Franklin diabase pole at 166 °E, 6 °N, α95 = 4°. At least 10 of the 11 new sites apparently lie outside the zone from within which Baffin dikes have yielded anomalous remanent magnetization directions. Thermomagnetic curves for representative material of the Baffin dikes indicate that the magnetic mineral of these rocks is almost pure magnetite. It does not explain the anomalous magnetization of the Franklin dikes that occur along the northeast coastal area.

Paleomagnetism of Steel Mountain and Indian Head anorthosites from western Newfoundland

1976 ◽  
Vol 13 (1) ◽  
pp. 75-83 ◽  
Author(s):  
G. S. Murthy ◽  
K. V. Rao
Keyword(s):  
Northern Hemisphere ◽  
Remanent Magnetization ◽  
Canadian Shield ◽  
Relative Rotation ◽  
Southeastern Part ◽  
Lower Paleozoic ◽  
Grenville Province ◽  
Grenville Orogeny ◽  
Paleomagnetic Pole

As part of studies of anorthosites from the northern hemisphere, the paleomagnetism of two anorthosite inliers at Indian Head and Steel Mountain in western Newfoundland is described. The six sites at Indian Head retain a stable remanent magnetization and yield a paleomagnetic pole at 8 °S, 157½° E(δp = 15°, δm = 20°). This is close to poles for anorthositic and other rock units from within the Grenville Province that represent magnetization of age 1000 m. y., suggesting that there is no relative rotation between western Newfoundland and the southeastern part of the Canadian Shield, at least since the time of the Grenville orogeny. The ten sites at Steel Mountain also retain a stable magnetization, which yields a paleomagnetic pole at 22½° S, 41 °W (δp = 8°, δm = 14°). This position is closer to lower Paleozoic poles from Newfoundland and thus probably represents a lower Paleozoic magnetization.

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