Borden dykes of Baffin Island, Northwest Territories: a Franklin U-Pb baddeleyite age and a paleomagnetic reinterpretation

1999 ◽  
Vol 36 (1) ◽  
pp. 65-73 ◽  
Author(s):  
Sally J Pehrsson ◽  
Kenneth L Buchan
Keyword(s):  
Northwest Territories ◽  
Remanent Magnetization ◽  
Paleomagnetic Data ◽  
Dyke Swarm ◽  
Baffin Island ◽  
Normal Faulting ◽  
Polar Wander ◽  
Baffin Bay ◽  
The North ◽  
Chemical Remanent Magnetization

U-Pb baddeleyite geochronology for two Borden diabase dykes of northern Baffin Island gives an intrusion age of ca. 720 Ma, coeval with the age established elsewhere for the Franklin igneous event. Thus, the Borden dykes belong to the Franklin dyke swarm, rather than forming a separate swarm that intruded at ca. 950-900 Ma, as has been suggested previously on the basis of paleomagnetism and K-Ar ages. As a result, the paleopole from the Borden dykes can no longer be utilized to help constrain the ca. 1050-850 Ma Grenville Loop of the North American polar wander path. Reevaluation of paleomagnetic data for the dykes of northern Baffin Island suggests that Borden dyke magnetizations resulted from superposition of a steeply directed component of chemical remanent magnetization on normal and reversed primary Franklin components. The overprint direction is consistent with a Cretaceous-Tertiary age and is likely related to normal faulting and graben development during the opening of Baffin Bay.

Paleomagnetism and U–Pb geochronology of the Clarence Head dykes, Arctic Canada: orthogonal emplacement of mafic dykes in a large igneous province

2009 ◽  
Vol 46 (3) ◽  
pp. 155-167 ◽  
Author(s):  
Steven W. Denyszyn ◽  
Don W. Davis ◽  
Henry C. Halls
Keyword(s):  
Remanent Magnetization ◽  
High Arctic ◽  
Large Igneous Province ◽  
Dyke Swarm ◽  
Canadian High Arctic ◽  
The North ◽  
Igneous Province ◽  
The Difference ◽  
Age Range ◽  
Chemical Remanent Magnetization

The north–south-trending Clarence Head dyke swarm, located on Devon and Ellesmere Islands in the Canadian High Arctic, has a trend orthogonal to that of the Neoproterozoic Franklin swarm that surrounds it. The Clarence Head dykes are dated by the U–Pb method on baddeleyite to between 716 ± 1 and 713 ± 1 Ma, ages apparently younger than, but within the published age range of, the Franklin dykes. Alpha recoil in baddeleyite is considered as a possible explanation for the difference in ages, but a comparison of the U–Pb ages of grains of equal size from both swarms suggests that recoil distances in baddeleyite are lower than those in zircon and that the Clarence Head dykes are indeed a distinctly younger event within the period of Franklin magmatism. The Clarence Head dykes represent a large swarm tangential to, and cogenetic with, a giant radiating dyke swarm ∼800 km from the indicated source. The preferred mechanism for the emplacement of the Clarence Head dykes is the exploitation of concentric zones of extension around a depleting and collapsing plume source. While the paleomagnetism of most Clarence Head dykes agrees with that of the Franklin dykes, two dykes have anomalous remanence directions, interpreted to be a chemical remanent magnetization carried by pyrrhotite. The pyrrhotite was likely deposited from fluids mobilized southward from the Devonian Ellesmerian Orogeny to the north that used the interiors of the dykes as conduits and precipitated pyrrhotite en route.

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

1976 ◽  
Vol 13 (4) ◽  
pp. 563-578 ◽  
Author(s):  
D. K. Bingham ◽  
M. E. Evans
Keyword(s):  
Northwest Territories ◽  
North American ◽  
Geomagnetic Field ◽  
Pole Position ◽  
The West ◽  
Stratigraphic Sequence ◽  
Polar Wander ◽  
Early Proterozoic ◽  
The North ◽  
Polarity Reversals

Paleomagnetic results from 55 sampling sites throughout the Stark Formation are reported. The known stratigraphic sequence of these sites enables the behaviour of the geomagnetic field in these remote times (1750 m.y.) to be elucidated. Two polarity reversals are identified and these represent potentially useful correlative features in strata devoid of index fossils. One of these is investigated in detail and indicates that behaviour of the geomagnetic field during polarity reversals was essentially the same in the early Proterozoic as it has been over the last few million years. The pole position (145°W, 15°S, dp = 3.5, dm = 6.9) lies far to the west of that anticipated from earlier results, implying further complexity of the North American polar wander curve. Possible alternatives to this added complexity are discussed.

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.

scholarly journals A re-assessesment of the shallow paleomagnetic inclinations of the Western Cyclades, Greece

2017 ◽  
Vol 47 (2) ◽  
pp. 498
Author(s):  
K.E. Bradley ◽  
E. Vassilakis ◽  
B.P. Weiss ◽  
L.H. Royden
Keyword(s):  
Middle Miocene ◽  
Volcanic Rocks ◽  
Aegean Sea ◽  
Convincing Evidence ◽  
Normal Faults ◽  
Polar Wander ◽  
The North ◽  
Stable Chemical ◽  
Field Geometry ◽  
Chemical Remanent Magnetization

Consistently shallow paleomagnetic inclinations measured in Early to Middle Miocene lacustrine and dacitic volcanic rocks of the Kymi-Aliveri basin have been cited as evidence for an anomalous geomagnetic field geometry or northward drift of the Aegean Sea region. We present new paleomagnetic data from the lacustrine beds that are instead not anomalously shallow and consistent with deposition near their present-day latitude as predicted by global apparent polar wander paths. Anomalously shallow inclinations and easterly declinations reported from the Oxylithos volcanics are an artifact of an inappropriate tilt correction. The excessively shallow paleomagnetic inclinations reported from the deformed Middle Miocene plutons on Mykonos and Naxos are consistent with reorientation of an original thermoremanent magnetization acquired during cooling below 580°C by subsequent ductile strain at temperatures of 400-500°C. Magnetization overprints observed in these rocks may reflect the acquisition of a stable chemical remanent magnetization lying parallel to the transposed high-temperature magnetization as the result of low-temperature (<350°C) maghemitization. We therefore find no convincing evidence for an anomalous Middle Miocene field geometry, northward drift of the Aegean, or back-tilting of the low-angle normal faults that constitute the North Cycladic Detachment System.

LANCASTER SOUND SHIPBORNE MAGNETOMETER SURVEY

1966 ◽  
Vol 3 (2) ◽  
pp. 223-235 ◽  
Author(s):  
D. L. Barrett
Keyword(s):  
Canadian Arctic ◽  
Vertical Movement ◽  
Baffin Island ◽  
Total Field ◽  
Sharp Rise ◽  
Near Surface ◽  
Baffin Bay ◽  
Devon Island ◽  
The North ◽  
Half Graben

The total magnetic field and the depth of water were measured along a ship's track of about 1 000 nautical miles during a shipborne magnetometer survey in Lancaster Sound and Baffin Bay in the eastern part of the Canadian Arctic Archipelago.Several magnetic anomalies on the extreme northern and southern boundaries of Lancaster Sound as well as to the east of Devon Island in Baffin Bay are characteristic of near-surface features. There is little magnetic relief in the center of the sound. The intensity of the total field decreases from south to north and then rises sharply immediately south of Devon Island. This sharp rise trends northeasterly in Baffin Bay.Several features are indicated by these data; (1) a near-surface basement on Devon and Baffin Islands, (2) a basement flexure north of Baffin Island, the whole of Lancaster Sound being downwarped with vertical movement of as much as 8 km in the north, (3) a regional fault extending along the south coast of Devon Island and trending northeast in Baffin Bay.It is concluded that this half-graben structure in. Lancaster Sound may be associated with a postulated median ridge between Greenland and North America.

Paleomagnetic and mineral magnetic constraints on Zn–Pb ore genesis in the Pend Oreille Mine, Metaline district, Washington, USA

2007 ◽  
Vol 44 (12) ◽  
pp. 1661-1673 ◽  
Author(s):  
S Johari Pannalal ◽  
David TA Symons ◽  
David L Leach
Keyword(s):  
Middle Jurassic ◽  
Remanent Magnetization ◽  
Mining District ◽  
Ore Genesis ◽  
The North ◽  
Thermal Data ◽  
Granite Batholith ◽  
Monoclinic Pyrrhotite ◽  
Mineral Magnetic ◽  
Chemical Remanent Magnetization

Zinc–lead mineralization in the Metaline mining district of northeastern Washington, USA, is hosted by the Cambrian Metaline Formation and is classified into Yellowhead-type (YO) and Josephine-type (JO) ore based on texture and mineralogy. Paleomagnetic results are reported for four Cambrian Metaline Formation sites, one Ordovician Ledbetter slate site, 12 YO and 13 JO (including two breccia sites) mineralization sites in the Pend Oreille Mine, and eight sites from the nearby Cretaceous Kaniksu granite batholith. Thermal and alternating field step demagnetization, saturation isothermal remanence analysis, and synthetic specimen tests show that the remanence in the host carbonates and Zn–Pb mineralization is carried mostly by pseudosingle (PSD) to single domain (SD) pyrrhotite and mostly by PSD to SD magnetite in the Kaniksu granite. Based on thermomagnetic measurements, sphalerite and galena concentrates and tailings from the mine’s mill contain hexagonal and monoclinic pyrrhotite. The postfolding characteristic remanent magnetization (ChRM), known thermal data, and paleoarc method of dating suggest that the Zn–Pb mineralization carries a primary chemical remanent magnetization (CRM), and Metaline Formation carbonates a secondary CRM that were acquired during the Middle Jurassic (166 ± 6 Ma) during the waning stages of the Nevadan orogeny. A paleomagnetic breccia test favours a solution-collapse origin for the Josephine breccia. Finally, the Kaniksu paleopole is concordant with the North American Cretaceous reference paleopole, suggesting the Kootenay terrane has not been rotated since emplacement of the batholith at ~94 Ma.

21.—The History of the North Water

1972 ◽  
Vol 72 (1) ◽  
pp. 231-241 ◽  
Author(s):  
Moira Dunbar ◽  
M. J. Dunbar
Keyword(s):  
Open Water ◽  
Baffin Island ◽  
The West ◽  
Baffin Bay ◽  
The North ◽  
Open Sea ◽  
Bylot Island ◽  
North Water ◽  
North Part ◽  
History Of

In 1616 William Baffin, coasting up the icebound west coast of Greenland, reported: ‘The first of July we were come into an open sea, in the latitude of 75 degrees 40 minutes, which a new revived our hope of a passage…’ (Purchas 1625). From this point, at an unspecified longitude in the north part of Melville Bay, he cruised for 12 days in open water, up the Greenland coast to 77°30'N and down the west side of Baffin Bay to Bylot Island, seeing and naming on the way Smith, Jones, and Lancaster sounds. From Bylot Island south he found ‘a ledge of ice between the shoare and us’ as he continued past Pond Inlet and down the coast of Baffin Island. This is the first mention in written records, and the first known navigation, of an area that became well known two centuries later as the ‘North Water’.

Paleomagnetism of Archean rocks from northwestern Ontario: Wabigoon gabbro, Wabigoon Subprovince

1983 ◽  
Vol 20 (12) ◽  
pp. 1805-1817 ◽  
Author(s):  
David J. Dunlop
Keyword(s):  
Remanent Magnetization ◽  
Natural Remanent Magnetization ◽  
Blocking Temperature ◽  
Virtual Geomagnetic Pole ◽  
Polar Wander ◽  
Apparent Polar Wander Path ◽  
Northwestern Ontario ◽  
Paleomagnetic Pole ◽  
Geomagnetic Pole ◽  
Chemical Remanent Magnetization

The Wabigoon gabbro of the Archean Wabigoon greenstone belt in northwestern Ontario preserves a univectorial natural remanent magnetization (NRM) with D = 246°, I = 12° (k = 19.5, α95 = 10.5°, N = 11 sites). The precision is reduced if sample means are averaged, however (k = 9.3, α95 = 9.2°, N = 29 samples). The paleomagnetic pole falls either at 160°W, 11°S (δp = 5.3°, δm = 10.6°), corresponding to an age of ~1300 Ma on the Laurentian apparent polar wander path, or the reverse of this, 20°E, 11° N, corresponding to a late Archean age (~2800 Ma). No ~1300 Ma igneous or metamorphic event is known in the area; a major west-northwest-trending dike about 9 km south of the gabbro yields a virtual geomagnetic pole at 122°W, 45°N and seems to be of Abitibi age (~2150 Ma) rather than Mackenzie age (~1250 Ma). A few gabbro samples and some greenstones from the intrusive baked zone have hybrid remanences in which a higher blocking temperature Kenoran-age (~2600 Ma) NRM is superimposed on the gabbro characteristic NRM. However, the Kenoran component may be a younger chemical remanent magnetization (CRM) residing in hematite. The hypothesis that the gabbro characteristic remanence is itself a hybrid of Kenoran and Keweenawan (~1100 Ma) NRM's, which would explain both the high between-sample scatter and the lack of a ~1300 Ma remagnetizing event, is considered but rejected because fewer than 10% of the gabbro samples exhibit multivectorial swings during alternating field or thermal cleaning. Two geomagnetic field reversals are recorded at interior sites, but only one or none is recorded near the margin of the intrusion. The different cooling histories of margin and interior, as well as the bulk of the other evidence, favour magnetization during initial cooling in late Archean time.

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