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.

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.

A detailed 40Ar/39Ar age study of an Abitibi dike from the Canadian Superior Province

1979 ◽  
Vol 16 (5) ◽  
pp. 1060-1070 ◽  
Author(s):  
J. A. Hanes ◽  
Derek York
Keyword(s):  
Canadian Shield ◽  
Superior Province ◽  
Low Grade ◽  
Polar Wander ◽  
Mafic Mineral ◽  
Fine Grained ◽  
Apparent Polar Wander Path ◽  
Step Heating ◽  
Apparent Age ◽  
Hydrothermal Event

40Ar/39Ar step-heating analyses were performed on 11 felsic and mafic mineral separates from a 90 m wide Precambrian diabase dike of the Abitibi swarm in the Superior Province of the Canadian Shield. Deuterically altered minerals from the dike interior define a primary age of 2150 ± 25 Ma. Updated ages, obtained from felsic separates within 30, and mafic within 1.5 m of the dike border, are evidence of a previously undetected 'Hudsonian' (1.7–1.8 Ga) hydrothermal event in the area. It is possible to distinguish the deuteric from the later hydrothermal alteration by both dating and petrographic methods. The data from this study demonstrate the successful application of 40Ar/39Ar dating to early Proterozoic dikes which have suffered low grade metamorphism. The ages support a north to south sense of motion of the Track 5 apparent polar wander path (APWP). A monotonic decrease in apparent age of felsic spectra indicates reactor induced recoil effects which are correlated with the fine-grained saussurite in the feldspar.

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.

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.

Geophysical characteristics of the continental crust along the Lithoprobe Eastern Canadian Shield Onshore–Offshore Transect (ECSOOT): a review

2002 ◽  
Vol 39 (5) ◽  
pp. 569-587 ◽  
Author(s):  
Jeremy Hall ◽  
Keith E Louden ◽  
Thomas Funck ◽  
Sharon Deemer
Keyword(s):  
Normal Incidence ◽  
Shear Zones ◽  
Canadian Shield ◽  
P Wave ◽  
Seismic Profiles ◽  
Grenville Province ◽  
Core Zone ◽  
The Core ◽  
Geodynamic Processes ◽  
Archean Crust

The Eastern Canadian Shield Onshore–Offshore Transect (ECSOOT) of the Lithoprobe program included 1200 km of normal-incidence seismic profiles and seven wide-angle seismic profiles across Archean and Proterozoic rocks of Labrador, northern Quebec, and the surrounding marine areas. Archean crust is 33–44 km thick. P-wave velocity increases downwards from 6.0 to 6.9 km/s. There is moderate crustal reflectivity, but the reflection Moho is unclear. Archean crust that stabilized in the Proterozoic is similar except for greater reflectivity and a well-defined Moho. Proterozoic crust has similar or greater thickness, variable lower crustal velocities, and strong crustal reflectivity. Geodynamic processes of Paleoproterozoic growth of the Canadian Shield are similar to those observed in modern collisional orogens. The suturing of the Archean Core Zone and Superior provinces involved whole-crustal shearing (top to west) in the Core Zone, linked to thin-skinned deformation in the New Quebec Orogen. The Torngat Orogen sutures the Nain Province to the Core Zone and reveals a crustal root, in which Moho descends to 55 km. It formed by transpression and survived because of the lack of postorogenic heating. Accretion of the Makkovik Province to the Nain Province involves delamination at the Moho and distributed strain in the juvenile arcs. Delamination within the lower crust characterizes the accretion of Labradorian crust in the southeastern Grenville Province. Thinning of the crust northwards across the Grenville Front is accentuated by Mesozoic extension that reactivates Proterozoic shear zones. The intrusion of the Mesoproterozoic Nain Plutonic Suite is attributed to a mantle plume ponding at the base of the crust.

Paleomagnetism of the Keweenawan Chipman Lake and Seabrook Lake carbonatite complexes, Ontario

1992 ◽  
Vol 29 (6) ◽  
pp. 1215-1223 ◽  
Author(s):  
D. T. A. Symons
Keyword(s):  
Magnetic Field ◽  
Remanent Magnetization ◽  
Pole Position ◽  
Alteration Zone ◽  
Contact Aureole ◽  
Isothermal Remanent Magnetization ◽  
Abitibi Subprovince ◽  
Normal Polarity ◽  
Reversed Polarity ◽  
Host Rocks

The Chipman Lake complex crops out as a series of carbonatite and related alkalic mafic dikes in the Wabigoon Subprovince of the Superior Province, whereas the Seabrook Lake complex crops out as an alkalic syenite – carbonatite stock in the Abitibi Subprovince. Paleomagnetic analysis was done on specimens from 23 and 19 sites located in and around the Chipman Lake and Seabrook Lake complexes, respectively, using detailed alternating-field and thermal step demagnetization and isothermal remanent magnetization tests. Contact tests with adjacent Archean host rocks show that both complexes retain a primary characteristic remanence (ChRM). The Chipman Lake's ChRM is retained in 11 dikes with normal polarity and one dike with reversed polarity and at one site with normal polarity and one site with reversed polarity from the fenite alteration zone. Its ChRM gives a pole position at 186°E, 38°N (dp = 7°, dm = 11°), which corresponds to a Keweenawan age of 1098 ± 10 Ma, suggesting that younger K–Ar amphibole ages do not date emplacement. The ChRM of the host rock, the Chipman Lake diorite stock, gives a pole at 49°E, 51°N (dp = 8°, dm = 13°), showing that it is not part of the Keweenawan complex but may be a 2.45 Ga Matachewan intrusive. The Seabrook Lake complex's ChRM is found at six normal polarity sites from within the complex and at four normal and three reversed polarity sites from within the fenitized Archean granite and Matachewan diabase of the contact aureole. It gives a pole position at 180°E, 46°N (dp = 11°, dm = 17°), which corresponds to a Keweenawan age of 1103 ± 10 Ma, agreeing with K/Ar biotite ages. The paleomagnetic data indicate that no significant motion on the Kapuskasing Structural Zone occurred after emplacement of the complexes excluding minor vertical uplift of less than about 4 km, and that there were multiple polarity transitions of a symmetric Earth's magnetic field during Keweenawan time.

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.

Paleomagnetism of the Lac St-Jean anorthosite and related rocks, Grenville Province, Quebec

1983 ◽  
Vol 20 (2) ◽  
pp. 246-258 ◽  
Author(s):  
K. L. Buchan ◽  
W. F. Fahrig ◽  
G. N. Freda ◽  
R. A. Frith
Keyword(s):  
North American ◽  
Regional Metamorphism ◽  
The Other ◽  
Central Portion ◽  
Grenville Province ◽  
Polar Wander ◽  
Thermal Demagnetization ◽  
The North ◽  
Apparent Polar Wander Path ◽  
Normal Polarity

Alternating field and thermal demagnetization study of the Lac St-Jean anorthosite and related rock units in the central portion of the exposed Grenville Province reveals two components of magnetization, one of reversed and the other of normal polarity. Both components are thought to have been acquired during the last regional metamorphism, which was sufficiently intense in this area (mostly amphibolite grade) to reset any earlier magnetization. Corresponding paleopoles at 193°W, 8°S (dm = 7.3°, dp = 4.6°) and 213°W, 19°S (dm = 10.5°, dp = 8.5°) lie along the 950–900 Ma segment of the recently calibrated Grenville track of the North American apparent polar wander path, a track that has thus far been defined largely by results from rock units of the western Grenville.

Malley diabase dykes of the Slave craton, Canadian Shield: U–Pb age, paleomagnetism, and implications for continental reconstructions in the early Paleoproterozoic1Geological Survey of Canada Contribution 20110114.

2012 ◽  
Vol 49 (2) ◽  
pp. 435-454 ◽  
Author(s):  
Kenneth L. Buchan ◽  
Anthony N. LeCheminant ◽  
Otto van Breemen
Keyword(s):  
Relative Orientation ◽  
Canadian Shield ◽  
Dyke Swarm ◽  
Slave Craton ◽  
Polar Wander ◽  
Thermal Demagnetization ◽  
Contact Test ◽  
Apparent Polar Wander Path ◽  
Close Proximity ◽  
Superior Craton

The NE-trending Malley dyke swarm, dated herein at 2231 ± 2 Ma (U–Pb baddeleyite), extends from the central Slave craton to the vicinity of the Kilohigok basin, and may continue farther to the northeast as the geochemically similar Brichta dyke swarm, having been offset sinistrally along the prominent Bathurst fault. It carries a characteristic high unblocking temperature paleomagnetic component of single polarity directed up SE (mean direction: D = 138.3°, I = –53.8°), with corresponding paleopole at 50.8°S, 50.0°W. Lower unblocking temperature components, in some cases directed down SE, similar to ca 1.75 Ga post-Hudsonian overprints, are easily removed using combined alternating field (AF) thermal demagnetization, but difficult to remove using AF cleaning alone. The characteristic remanence has not been demonstrated primary, but is significantly older than 2.03 Ga, the age of Lac de Gras dykes, based on a baked contact test at a Lac de Gras – Malley dyke intersection. In addition, an E- to ESE-trending dyke carries a down WNW remanence, typical of 2.19 Ga Dogrib dykes near Yellowknife, suggesting that regional overprinting has not affected the study area since Dogrib emplacement, and that the Malley remanence was acquired at or shortly after Malley emplacement. Comparing Malley and Lac de Gras paleopoles with the 2.22–2.00 Ga Superior craton apparent polar wander path indicates that the two cratons were (i) not in their present relative orientation at 2.23 or 2.03 Ga, and (ii) likely not drifting in close proximity to one another as parts of a single (super)continent throughout the 2.23–2.03 Ga interval.

Paleomagnetic Results from the Jurassic Topley Intrusions near Endako, British Columbia

1973 ◽  
Vol 10 (7) ◽  
pp. 1099-1108 ◽  
Author(s):  
D. T. A. Symons
Keyword(s):  
British Columbia ◽  
Lower Cretaceous ◽  
Remanent Magnetization ◽  
Upper Jurassic ◽  
Pole Position ◽  
Upper Triassic ◽  
Polar Wander ◽  
Quartz Monzonite ◽  
Reversed Polarity ◽  
North American Craton

The Upper Jurassic Topley Intrusions intrude rocks of the tectonically stable Interior Plateau in central British Columbia. A stable primary remanent magnetization of both normal and reversed polarity was isolated after a.f. demagnetization in 19 of 22 sites (109 cores; 208 specimens) representing several of the plutonic units present in this sialic complex of quartz monzonite affinity near Endako, B.C. The unit mean remanence directions support some petrological correlations suggested by Carr, Bright, and White et al., but do not support others. The pole position derived from 13 sites representing 6 plutonic units with a K–Ar radiomelric age of 139 ± 4 m.y. (White et al.) is 128.6 °E, 70.0 °N(δm = 14.4°; δp = 11.4°). This position indicates a smooth polar wander path during the Jurassic between the well defined Upper Triassic and Lower Cretaceous pole positions. It also indicates that the northern Interior Plateau has not been tectonically rotated or translated since emplacement relative to the stable North American craton.

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