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
Geophysics ◽  
1967 ◽  
Vol 32 (4) ◽  
pp. 678-707 ◽  
Author(s):  
M. L. Richards ◽  
V. Vacquier ◽  
G. D. Van Voorhis

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.


1975 ◽  
Vol 12 (1) ◽  
pp. 52-61 ◽  
Author(s):  
M. E. Evans ◽  
D. K. Bingham ◽  
E. W. McMurry

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.


1980 ◽  
Vol 17 (7) ◽  
pp. 807-822 ◽  
Author(s):  
P. W. Schmidt

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.


Geotectonics ◽  
2021 ◽  
Vol 55 (2) ◽  
pp. 179-193
Author(s):  
V. Yu. Vodovozov ◽  
G. L. Leitchenkov ◽  
M. S. Egorov ◽  
N. A. Gonzhurov ◽  
E. V. Mikhalsky

1983 ◽  
Vol 20 (2) ◽  
pp. 275-289 ◽  
Author(s):  
K. W. Christie ◽  
W. F. Fahrig

Northern Baffin Island is intersected by spectacular swarms of predominantly northwesterly trending diabase dykes. Cross-cutting relationships, K–Ar ages, and paleomagnetic contact tests indicate that these dykes represent at least two major episodes of Hadrynian igneous activity. The Borden dykes were emplaced during the earlier of these episodes. They are about 950 Ma old and have a paleomagnetic pole position of 153.3°E, 26.7°S, δm = 8.6e, δp = 6.1°. The later episode saw the emplacement of the previously defined Franklin dykes, which are about 750 Ma old. The newly defined Borden pole lies at the southern extremity of the Grenville Loop and has an age consistent with poles of similar position that were derived from rocks of the Grenville Province.All of the dykes probably reflect tension acting in an east-northeast–west-southwest direction. The directions of thick northwest trending dykes, which form a considerable angle to that expected from east-northeast tension, are thought to have been controlled by earlier (circa 1200 Ma) fractures of the Borden fault zones. The two main surges of magma may coincide with two -periods of Hadrynian uplift in the Boothia Peninsula area to the west.


1971 ◽  
Vol 8 (4) ◽  
pp. 455-467 ◽  
Author(s):  
W. F. Fahrig ◽  
E. Irving ◽  
G. D. Jackson

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.


1969 ◽  
Vol 6 (4) ◽  
pp. 679-688 ◽  
Author(s):  
W. F. Fahrig ◽  
D. L. Jones

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.


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