The petrology, geochemistry, and remanent magnetization of metabasalts and metagabbros in the Lac Patu – Fort McKenzie region, New Quebec Territory

1976 ◽  
Vol 13 (6) ◽  
pp. 838-846 ◽  
Author(s):  
Maurice K.-Seguin
Keyword(s):  
Remanent Magnetization ◽  
Pole Position ◽  
Magnetic Memory ◽  
Paleomagnetic Pole ◽  
Lower Proterozoic ◽  
Pertinent Information ◽  
The Mean ◽  
The Stability ◽  
Anhysteretic Magnetization ◽  
Chemical Description

One hundred and five specimens were collected from 40 different sites in northwest-striking metabasalts and metagabbros of Lower Proterozoic (Aphebian) age in the northeastern part of the Labrador Trough (longitude: 69 °W, latitude: 57 °N). The radiogenic age determinations of surrounding rocks of the same age yielded 1860 m.y. A petrological and chemical description of the rocks is included. The chemical results for total Fe, MgO, and Na2O + K2O combined, drawn on a ternary diagram show that the metabasalts and metagabbros fall in the tholeiite field. Magnetite (with some occasional 5% ulvospinel) is the most frequent magnetic memory carrier; pyrrhotite is less commonly found. In order to obtain some pertinent information relative to the stability of the NRM component, step-wise alternating field demagnetization was conducted on 40% of the specimens and the others were demagnetized at a specific AF intensity. In 35% of the specimens, the AF demagnetization process induced an anhysteretic magnetization component above 250 Oe. A secondary isothermal remanent magnetization of lesser stability was often detected in the 50–150 Oe range. Tilting of the formations sometimes increased and sometimes decreased the dispersion of the NRM vectors. After tilting the lithological units that were AF demagnetized, the mean paleomagnetic pole position is 152 °E, 20° S (dm = 14°,dp = 07°, K = 34), with at least one reversal.

scholarly journals Paleomagnetism of the Caldwell lavas, Eastern Townships, Québec.

2010 ◽  
Vol 31 (1) ◽  
Author(s):  
M. K. SEGUIN
Keyword(s):  
Lower Cambrian ◽  
Remanent Magnetization ◽  
Magnetic Memory ◽  
Early Cambrian ◽  
Metavolcanic Rocks ◽  
Basaltic Composition ◽  
Oriented Samples ◽  
Pertinent Information ◽  
Reversed Polarity ◽  
The Stability

Forty two oriented samples (97 specimens) were obtained from 17<br />sites in metavolcanic rocks from the Caldwell Group of the Appalachians<br />of Southern Québec (longitude: 71u00'-71"30' W, latitude: 46°00'-46"10'N).<br />These metavolcanics of Lower Cambrian age are massive or pillowed lavas<br />of andesitic and mainly basaltic composition metamorphosed to the<br />sub-greenschist facies. Magnetite and occasionally hematite are the frequent<br />magnetic memory carrier.<br />In order to obtain some pertinent information relative to the stability<br />of the remanent magnetization component, stepwise alternating field<br />demagnetization was conducted on 35% of the specimens and the others<br />were demagnetized at an optimum alternating field. After AF treatment,<br />the paleopole position of the tilted formation from 16 localities is 148°E,<br />43°N (dp=11.3°, dm = 22.4°). After omission of 3 localities for which<br />a95>30°, the new paleopole position obtained is 173°E, 26°N. This formation<br />of Early Cambrian age is characterized by a reversed polarity.

MANICOUAGAN, QUEBEC, PALEOMAGNETIC RESULTS

1967 ◽  
Vol 4 (4) ◽  
pp. 641-649 ◽  
Author(s):  
W. A. Robertson
Keyword(s):  
North American ◽  
Remanent Magnetization ◽  
Thermal Studies ◽  
Pole Position ◽  
The Mean ◽  
Paleomagnetic Poles

The remanent magnetization of dacitic material from Manicouagan, Quebec, was examined. Laboratory thermal studies support the view that viscous buildup in situ was small and secondary components insignificant. A pole position of 89 °E., 57 °N. is calculated from the mean direction of 6 sites. Comparison with other North American paleomagnetic poles points to a possible Triassic age for the formation of the material.

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, structure, and longitudinal correlation of Middle Precambrian dykes from northwestern Ontario and Minnesota

1986 ◽  
Vol 23 (2) ◽  
pp. 142-157 ◽  
Author(s):  
H. C. Halls
Keyword(s):  
Continental Margin ◽  
Pole Position ◽  
Dyke Swarm ◽  
Time Interval ◽  
Northwestern Ontario ◽  
Longitudinal Correlation ◽  
Paleomagnetic Pole ◽  
The Mean ◽  
Dyke Swarms ◽  
Sufficient Proof

A primary magnetization about 2.1 Ga old is well preserved in the Kenora–Kabetogama dyke swarm in Minnesota and Ontario. Its direction, the mean for 12 dykes, incorporating results from 30 paleomagnetic sites, is 115.9°, −55.6°, yielding a paleomagnetic pole position of latitude 42.7°S, longitude 4.2°E (dm = 7.3°, dp = 5.2°).The primary nature of the magnetization can be demonstrated using geochemistry to correlate individual dykes over distances that can exceed 300 km. Whereas the remanence direction varies between dykes, it remains constant along a dyke, sufficient proof that it was formed during initial cooling of the intrusion.A weak, longitudinal increase in hydrous alteration, MgO content, and degree of magnetic overprinting is observed as the swarm is followed to the south and may reflect increasing proximity to a Precambrian continental margin that underwent rifting, sedimentation, and deformation during the time interval 2.2–1.6 Ga BP. Although the cause of the longitudinal changes in terms of margin evolution can only be surmised, the results illustrate the potential of dyke swarms as sensitive indicators of how shield terrains may respond to events occurring around their margins.

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.

The paleomagnetism of the Michikamau anorthositic intrusion, Labrador

1968 ◽  
Vol 5 (5) ◽  
pp. 1139-1144 ◽  
Author(s):  
G. S. Murthy ◽  
W. F. Fahrig ◽  
D. L. Jones
Keyword(s):  
Magnetic Field ◽  
North America ◽  
Pole Position ◽  
Alternating Magnetic Field ◽  
Paleomagnetic Pole ◽  
The Stability

Twenty-nine oriented cores have been collected from six sites in the Michikamau Intrusion in Labrador. This had previously been well dated at 1400 m.y. by the potassium–argon method. A fold test has been applied to the paleomagnetic results after alternating magnetic field demagnetization. The results suggest that the magnetization was acquired with the rocks in their present attitudes. The stability of the magnetization has been well tested and it is concluded that the observed magnetization is thermo-remanent and represents the direction of the earth's field at the intrusion at the time of its formation. The paleomagnetic pole position for the intrusion lies at 0.5° S, 144.7° W, with A95 = 5.6°. It is difficult to compare this result with most other Precambrian results from North America due to uncertainties in age equivalences. However, a comparison with recently published results from well-dated rocks from Colorado–Wyoming suggests there have been no large relative movements between this region and Labrador for the last 1400 million years.

The paleomagnetism of the Croker Island Complex, Ontario, Canada

1969 ◽  
Vol 6 (2) ◽  
pp. 213-218 ◽  
Author(s):  
H. C. Palmer
Keyword(s):  
North America ◽  
Remanent Magnetization ◽  
Pole Position ◽  
Lake Huron ◽  
Time Interval ◽  
Significant Shift ◽  
Paleomagnetic Pole ◽  
Oriented Samples

Meaningful paleomagnetic results were obtained from 23 of 30 oriented samples from the Croker Island Complex, North Channel of Lake Huron, Canada. The age of the complex is estimated to be 1475 ± 50 m.y. from a Rb–Sr isochron. The paleomagnetic pole calculated from the directions of remanent magnetization after partial ac demagnetization is 143 °West, [Formula: see text] North. This result, when compared with other paleomagnetic results from North America, indicates little or no polar wandering in the time interval 1.48 b.y. to 1.1 b.y. However, a significant shift in the pole position is indicated during the time interval 1.7 to 1.48 b.y.

From the stability of cells to the mean behavior of growth fronts : A directional solidification study

2001 ◽  
Vol 11 (PR6) ◽  
pp. Pr6-169-Pr6-178 ◽  
Author(s):  
A. Pocheau ◽  
M. Georgelin
Keyword(s):  
Directional Solidification ◽  
The Mean ◽  
The Stability

Injuries to the Coronoid Process of the Ulna with Involvement of the Lesser Sigmoid Notch

2020 ◽  
Author(s):  
Valentin Rausch ◽  
Sina Neugebauer ◽  
Tim Leschinger ◽  
Lars Müller ◽  
Kilian Wegmann ◽  
...  
Keyword(s):  
Fragment Size ◽  
Coronoid Process ◽  
Annular Ligament ◽  
Concomitant Injuries ◽  
Proximal Ulna ◽  
Sigmoid Notch ◽  
Coronoid Fractures ◽  
The Mean ◽  
The Stability ◽  
Arthritic Changes

Abstract Introduction This study aimed to describe the involvement of the lesser sigmoid notch in fractures to the coronoid process. We hypothesized that injuries to the lateral aspect of the coronoid process regularly involve the annular ligament insertion at the anterior lesser sigmoid notch. Material and Methods Patients treated for a coronoid process fracture at our institution between 06/2011 and 07/2018 were included. We excluded patients < 18 years, patients with arthritic changes or previous operative treatment to the elbow, and patients with concomitant injuries to the proximal ulna. In patients with involvement of the lesser sigmoid notch, the coronoid height and fragment size (anteroposterior, mediolateral, and craniocaudal) were measured. Results Seventy-two patients (mean age: 47 years ± 17.6) could be included in the study. Twenty-one patients (29.2%) had a fracture involving the lateral sigmoid notch. The mean anteroposterior fragment length was 7 ± 1.6 mm. The fragment affected a mean of 43 ± 10.8% of the coronoid height. The mean mediolateral size of the fragment was 10 ± 5.0 mm, and the mean cranio-caudal size was 7 ± 2.7 mm. Conclusion Coronoid fractures regularly include the lesser sigmoid notch. These injuries possibly affect the anterior annular ligament insertion which is important for the stability of the proximal radioulnar joint and varus stability of the elbow.

Instant 99mTc-Labelled Glucoheptonate Kit for Kidney Imaging

1983 ◽  
Vol 22 (05) ◽  
pp. 246-250 ◽  
Author(s):  
M. Al-Hilli ◽  
H. M. A. Karim ◽  
M. H. S. Al-Hissoni ◽  
M. N. Jassim ◽  
N. H. Agha
Keyword(s):  
Sodium Hydroxide Solution ◽  
Normal Subjects ◽  
Organ Distribution ◽  
Stable Complex ◽  
Scintillation Camera ◽  
Ph Adjustment ◽  
The Mean ◽  
The Stability ◽  
Kidney Imaging ◽  
Mean Concentration

Gelchromatography column scanning has been used to study the fractions of reduced hydrolyzed 99mTc, 99mTc-pertechnetate and 99mTc-chelate in a 99mTc-glucoheptonate (GH) preparation. A stable high labelling yield of 99mTc-GH complex in the radiopharmaceutical has been obtained with a concentration of 40-50 mg of glucoheptonic acid-calcium salt and not less than 0.45 mg of SnCl2 2 H2O at an optimal pH between 6.5 and 7.0. The stability of the complex has been found significantly affected when sodium hydroxide solution was used for the pH adjustment. However, an alternative procedure for final pH adjustment of the preparation has been investigated providing a stable complex for the usual period of time prior to the injection. The organ distribution and the blood clearance data of 99mTc-GH in rabbits were relatively similar to those reported earlier. The mean concentration of the radiopharmaceutical in both kidneys has been studied in normal subjects for one hour with a scintillation camera and the results were satisfactory.

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