New Paleomagnetic Results from the Upper Belt – Purcell Supergroup of Alberta

1975 ◽  
Vol 12 (1) ◽  
pp. 52-61 ◽  
Author(s):  
M. E. Evans ◽  
D. K. Bingham ◽  
E. W. McMurry
Keyword(s):  
Pole Position ◽  
Canadian Shield ◽  
Considerable Potential ◽  
Paleomagnetic Pole ◽  
Belt Supergroup ◽  
Order Of Magnitude ◽  
Global Time ◽  
Geomagnetic Polarity ◽  
Apparent Conflict

Stable remanent directions have been obtained from fifteen sites located in the Purcell, Shepard and Kintla Formations of the upper Belt – Purcell Supergroup. The geomagnetic polarity sequence revealed by these and other studies suggests that the frequency of reversals was probably an order of magnitude lower than that observed over the last few million years. The polarity transitions have considerable potential as regional, and possibly, global, time lines for geological correlation.The paleomagnetic pole obtained (142 °W, 17 °S, dp = 4°, dm = 7°) agrees well with other results from the Belt Supergroup. It falls in a cluster of poles derived from various geological provinces of the Canadian Shield, which may imply that the shield was an integral unit as early as 1400 m.y. ago. However, the constancy of the pole position obtained from Belt rocks thought by some workers to be as young as 1100 m.y. conflicts with the large northward polar excursion (the Logan Loop) derived from other provinces. Possible explanations of this apparent conflict are discussed.

Paleomagnetism of the Franklin Diabases

1971 ◽  
Vol 8 (4) ◽  
pp. 455-467 ◽  
Author(s):  
W. F. Fahrig ◽  
E. Irving ◽  
G. D. Jackson
Keyword(s):  
Pole Position ◽  
Canadian Shield ◽  
Baffin Bay ◽  
Late Proterozoic ◽  
Paleomagnetic Pole ◽  
Early Tertiary ◽  
Davis Strait

Diabase intrusions, which have a probable mean age of 675 m.y., occur in a giant arc across the northern part of the Canadian Shield. They have a paleomagnetic pole position of 167° E, 8° N (α95 = 5°), and at least one reversal. The paleomagnetic results indicate that the northern Canadian Shield was near the equator at the time of intrusion, and this is in agreement with evidence of warm conditions of deposition found in erosional remnants of related late Proterozoic sediments. Some of the diabase, near the shores of Davis Strait, may have been partially remagnetized during the opening of Baffin Bay in the early Tertiary.

Paleomagnetic evidence for the extent of Mackenzie igneous events

1969 ◽  
Vol 6 (4) ◽  
pp. 679-688 ◽  
Author(s):  
W. F. Fahrig ◽  
D. L. Jones
Keyword(s):  
Volcanic Rocks ◽  
Pole Position ◽  
Canadian Shield ◽  
Paleomagnetic Data ◽  
Paleomagnetic Pole ◽  
Great Slave Lake ◽  
The Mean ◽  
Coppermine River ◽  
Age Determinations ◽  
Middle Proterozoic

North-northwesterly striking Mackenzie diabase dikes of middle-Proterozoic (Helikian) age are profuse in the western part of the Canadian Shield. Published paleomagnetic data on dikes of this trend in Mackenzie District, on the Muskox Intrusion, the Coppermine River volcanic rocks, and the Sudbury dikes suggest that they are all products of closely related igneous events. This paper presents paleomagnetic data that suggest that the intrusion of extensive diabase sheets in the East Arm of Great Slave Lake, and of dikes as far to the northeast as Melville Peninsula and as far to the southeast as Manitoba, were also parts of these events. The mean paleomagnetic pole position for the Mackenzie dikes and for related intrusive and extrusive rocks is [Formula: see text], 171 °W with [Formula: see text]. Radioactive age determinations, some of which are unpublished, indicate an age of about 1200 m.y. for the formation of these rocks. It is suggested that for convenience all of these apparently related intrusive and extrusive igneous episodes be referred to as Mackenzie igneous events.

Paleomagnetism of the Michael Gabbro and Possible Evidence of the Rotation of Makkovik Subprovince

1972 ◽  
Vol 9 (10) ◽  
pp. 1287-1296 ◽  
Author(s):  
W. F. Fahrig ◽  
A. Larochelle
Keyword(s):  
North America ◽  
Remanent Magnetization ◽  
Pole Position ◽  
Canadian Shield ◽  
Main Body ◽  
Central Coast ◽  
Tectonic Event ◽  
South Central ◽  
Paleomagnetic Pole ◽  
Paleomagnetic Study

The Michael gabbro forms a belt of thick, predominantly southerly-dipping sheets which extends 200 km inland from the south-central coast of Labrador. The intrusions lie largely within the Makkovik subprovince, have a radioisotopic age of 1500 m.y., and are reversely magnetized with a paleomagnetic pole position of 163 °E, 10 °N. The paleomagnetic results indicate that most of the rocks internal to this belt have not been deformed since the intrusions acquired a stable remanent magnetization, presumably at the time of cooling 1500 m.y. ago. However, the Michael pole position differs significantly from those of rocks of similar age elsewhere in North America. This suggests rotation of the block containing the Michael intrusions relative to these other rocks. The Aillik dikes which also lie within the Makkovik sub-province have a radioisotopic age of about 1100 m.y. and a pole position consistent with that of rocks of similar age elsewhere in the Canadian Shield. The postulated Michael rotation must then have taken place between 1500 and 1100 m.y. ago.The rock at two of the most southerly sites sampled for paleomagnetic study proved to be magnetically unstable and the rock at a third such site, though stably magnetized has a magnetization significantly different from the main body of Michael gabbro intrusions. These three sites may indicate a post-consolidation thermal and tectonic event and their position may help define the Grenville Front in this region.

Cambro-Ordovician paleomagnetic pole position and rubidium-strontium total rock isochron for charnockitic rocks from Mirnyy Station, East Antarctica

1972 ◽  
Vol 16 (3) ◽  
pp. 433-438 ◽  
Author(s):  
D MCQUEEN ◽  
C SCHARNBERGER ◽  
L SCHARON ◽  
M HALPERN
Keyword(s):  
Pole Position ◽  
East Antarctica ◽  
Paleomagnetic Pole

CALCULATION OF THE MAGNETIZATION OF UPLIFTS FROM COMBINING TOPOGRAPHIC AND MAGNETIC SURVEYS

Geophysics ◽  
1967 ◽  
Vol 32 (4) ◽  
pp. 678-707 ◽  
Author(s):  
M. L. Richards ◽  
V. Vacquier ◽  
G. D. Van Voorhis
Keyword(s):  
Pacific Ocean ◽  
Horizontal Plane ◽  
Large Scale ◽  
Geomagnetic Latitude ◽  
Pole Position ◽  
Present Position ◽  
Paleomagnetic Pole ◽  
The Pacific ◽  
Geomagnetic Pole ◽  
The Pacific Ocean

The direction and magnitude of the magnetization of a uniformly magnetized structure can be computed by combining topographic and magnetic surveys. The previously reported method has been extended to include more than one structure, each possessing its particular magnetization. Also, the bottom of the structure need not be a horizontal plane but can be an arbitrary surface. The method was applied to 21 seamounts, one laccolith and two Aleutian volcanoes. Four of the seamounts were found to be reversely magnetized. The virtual paleomagnetic pole positions for 16 Pacific Ocean seamounts, representing three widely separated locations, are significantly different from the present geomagnetic pole position but near Mesozoic virtual pole positions from Australia. For two locations, radiometric age determinations give an average date for their formation in the Cretaceous. The apparent 30 degree shift in geomagnetic latitude of the seamounts is interpreted as the result of large scale movements of the Pacific Ocean floor or, alternatively, as the result of the paleomagnetic equator being north of its present position in the Pacific during the growth of the seamounts.

Paleomagnetism of the Mealy Mountain Anorthosite Suite and of the Shabogamo Gabbro, Labrador, Canada

1974 ◽  
Vol 11 (1) ◽  
pp. 18-29 ◽  
Author(s):  
W. F. Fahrig ◽  
K. W. Christie ◽  
E. J. Schwarz
Keyword(s):  
Pole Position ◽  
Canadian Shield ◽  
The South ◽  
Clockwise Rotation ◽  
End Points ◽  
Stable Component ◽  
Sample Area ◽  
Initial Magnetization ◽  
East Component ◽  
Middle Proterozoic

Two stable, ancient, N.R.M. components were isolated by a.f. demagnetization of samples from 29 sites in the Helikian (Middle Proterozoic) anorthosite and adamellite suites of the Mealy Mountains. The directions of the two components are chiefly to the northwest, 20° upward (northwest component) and to the east, 65 °downward (east component). The northwest direction is thought to be the primary igneous T.R.M. and no reversely magnetized sites with this direction were encountered in the Mealy suite. The 11 sites from which the northwesterly component was isolated yielded a mean pole at 179 °W, 8 °N, α95 = 12°. This is some distance away from poles derived from rocks of comparable age from elsewhere in the Canadian Shield and may reflect a 50° clockwise rotation of this section of the Grenville Orogen relative to the Superior after the initial magnetization of the Mealy rocks. Evidence of a second stable component was found in 14 sites (east component); 11 of these are reversely magnetized and three are normally magnetized. The 14 sites with easterly (and reversed easterly) magnetization yielded a combined pole for this component at 182 °W, 38 °S, α95 = 9°. This pole position suggests that the east component was acquired after the rotation of this part of the Grenville Orogen. The cores from 3 sites exhibited two clear end-points during a.f. demagnetization and thus contain both the northwest and the east component.The Helikian Shabogamo Gabbro at the south end of the Labrador Trough was sampled at 13 sites on a line extending 80 km north from the Grenville Front. After a.f. cleaning these sites yielded a pole at 171 °W, 10 °N, α95 = 12°. This pole lies about 20° northwest of poles for rocks of similar age in the Superior Orogen so it is suggested that the rocks of the sample area, though lying a bit north of the line generally accepted as the 'Grenville Front', have been rotated clockwise (about 20°) since intrusion of the gabbro.

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.

Paleomagnetism of igneous rocks from the Belcher Islands, Northwest Territories, Canada

1980 ◽  
Vol 17 (7) ◽  
pp. 807-822 ◽  
Author(s):  
P. W. Schmidt
Keyword(s):  
North America ◽  
Northwest Territories ◽  
Igneous Rock ◽  
Pole Position ◽  
Igneous Rocks ◽  
Hudson Bay ◽  
Plate Model ◽  
Polar Wander ◽  
Apparent Polar Wander Path ◽  
Paleomagnetic Pole

Paleomagnetic results from igneous rock units on the Belcher Islands, Hudson Bay, are described. Fold tests for all units studied, as well as a contact test for the intrusive bodies, indicate that both primary (initial), and secondary (post-folding) magnetizations are present.The paleomagnetic pole position from primary directions of the oldest unit studied, the Eskimo volcanics, is situated at 40°S, 002°E (A95 = 12°) and is similar to that derived from equivalent volcanics on the mainland. The younger volcanic unit studied, the Flaherty volcanics, yielded a pole position from primary directions at 0°, 244°E (A95 = 7°). The Haig intrusions, associated with these younger volcanics, yields an almost identical pole position at 1°N, 247°E (A95 = 6°), being derived from directions which are shown to be not only pre–folding but also date from initial cooling. The Eskimo volcanics, which have been more deeply buried than the Flaherty (upper) volcanics, carry substantial components of secondary (post-folding) magnetization which yield a pole position at 19°N, 243°E (A95 = 15°), about 20° north of the pole positions derived from the youngest units.It is argued that the apparent polar wander path (APWP) constructed for the Belcher Islands is representative of the mainland Ungava Craton. Comparison with the equivalent APWP from elsewhere in North America shows that the two APWP's are at variance. Although a two-plate model could be advanced, perhaps a more conservative interpretation is to extend the existing North American APWP eastward to include the Belcher–Ungava APWP, that is, to favour a one-plate model.

Comparison of MAGSAT and low-level aeromagnetic data over the Canadian Shield: implications for GRM

1985 ◽  
Vol 22 (9) ◽  
pp. 1241-1247 ◽  
Author(s):  
J. Arkani-Hamed ◽  
D. W. Strangway ◽  
D. J. Teskey ◽  
P. J. Hood
Keyword(s):  
Magnetic Anomaly ◽  
Canadian Shield ◽  
Geological Mapping ◽  
Aeromagnetic Data ◽  
Research Mission ◽  
Geological Features ◽  
Order Of Magnitude ◽  
Band Limited ◽  
Anomaly Map ◽  
The One

Band-limited magnetic anomalies over the Canadian Shield, for wavelengths of ~500–2200 km, derived from the magnetometer satellite (MAGSAT) data correlate peak for peak with the corresponding anomalies derived from the aeromagnetic data. This suggests that the anomalies detected by MAGSAT are physically meaningful. A new potential field satellite, Geopotential Research Mission (GRM), has been proposed to fly at about 160 km altitude. The magnetic anomaly map that can be derived from the GRM data is expected to have a resolution about an order of magnitude higher than the one derived from MAGSAT data. A magnetic anomaly map of the Canadian Shield, which is expected to derive from the GRM data, is shown based on the aeromagnetic data. The map delineates many major geological features quite clearly and illustrates the importance of the GRM mission for global geological mapping.

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