Constraints on the nature of the Kapuskasing structural zone from the study of Proterozoic dyke swarms

1994 ◽  
Vol 31 (7) ◽  
pp. 1182-1196 ◽  
Author(s):  
H. C. Halls ◽  
H. C. Palmer ◽  
M. P. Bates ◽  
Wm. C. Phinney
Keyword(s):  
Magnetic Field ◽  
Fault Zone ◽  
Magnetic Polarity ◽  
High Alumina ◽  
Superior Province ◽  
Structural Studies ◽  
The West ◽  
Early Proterozoic ◽  
Dyke Swarms ◽  
Broad Scale

Petrochemical, paleomagnetic, and structural studies on Early Proterozoic dyke swarms show that the rocks of the Kapuskasing structural zone (KSZ), central Superior Province, were upthrust about 10–15 km along the Ivanhoe Lake fault after intrusion of 2.04 Ga Kapuskasing dykes. This uplift was part of a more widespread deformation in flanking terranes that involved sinistral motion along north–north-northwest-trending faults, dextral displacement along east-northeast–northeast-trending faults, and a distortion of the 2.45 Ga Matachewan swarm to the west and northwest of the Ivanhoe Lake fault. The most spectacular demonstration that the KSZ is largely a product of Proterozoic deformation is that Matachewan dykes change their magnetic polarity on crossing the zone, a consequence of remanence acquisition at deep crustal levels being delayed until after a reversal of the earth's magnetic field and prior to uplift of the dykes.Matachewan and Kapuskasing dykes within the amphibolite- to granulite-grade rocks of the KSZ are relatively fresh and contain a high-alumina green amphibole and feldspar laths that exhibit tea-coloured clouding due to the presence of submicroscopic inclusions of magnetite. These features may be diagnostic of crystallization at deeper crustal levels because they are found in regions where Rb–Sr biotite ages from tonalites suggest broad-scale uplift of the crust after about 2 Ga. About 50 km west of the KSZ, dykes exhibiting clouded feldspar and high-alumina amphiboles occur on the upthrown side of the Budd Lake fault zone, which has a trend similar to that of the Ivanhoe Lake fault. Therefore a second thrust block may exist, raising the possibility that the KSZ represents the basal member of a series of imbricate thrust slices that extends westwards from the Ivanhoe Lake fault. Radiometric age data suggest that the region affected by this Early Proterozoic deformation continues to the northwest for a further 300 km.

Rb–Sr biotite and whole-rock data from the Kapuskasing uplift and their bearing on the cooling and exhumation history

1994 ◽  
Vol 31 (7) ◽  
pp. 1172-1181 ◽  
Author(s):  
J. A. Percival ◽  
Z. E. Peterman
Keyword(s):  
Fault Zone ◽  
Spatial Relationship ◽  
Paleomagnetic Data ◽  
Isotopic Ratios ◽  
The West ◽  
Rapid Cooling ◽  
Early Proterozoic ◽  
Granitoid Rocks ◽  
Relationship Of ◽  
Exhumation History

Rb–Sr isotopic ratios were measured on biotite and whole rocks from a suite of 21 granitoid rocks from the southern Kapuskasing uplift. Results of 18 of the whole-rock analyses fall on an isochron with an age of 2.677 ± 0.057 Ga and Sri = 0.70080. Biotite model ages range from 2.50 to 1.93 Ga in a general spatial relationship of decreasing age with depth in the structural section as calibrated with the igneous hornblende barometer for tonalitic rocks and garnet–pyroxene barometers for granulites. Near the Michipicoten belt in the west, biotite ages of ~ 2 Ga reflect disturbances also recorded by paleomagnetic and whole-rock Rb–Sr systems. To the east, in a 70 km long northwest–southeast transect toward the Ivanhoe Lake fault zone, ages decrease from 2.50 to 1.95 Ga. In a southern transect ages are in the range 2.30–2.38 Ga to within 15 km of the fault, reflecting consistent erosion levels corresponding to ~ 0.53 MPa, but decrease to 1.93 Ga to the east, in concert with paleopressures in the 0.7–1.0 GPa range.A plateau of low Rb–Sr biotite dates is not evident, suggesting that the Kapuskasing uplift event exposed a frozen-in cooling profile, rather than setting the Rb–Sr clock by rapid cooling of the rocks from above their closure temperature. The youngest biotite date of 1.93 Ga therefore provides a maximum age for uplift, consistent with paleomagnetic data from Archean rocks and Early Proterozoic dykes, but in conflict with some K–Ar and 40Ar/39Ar biotite age data.

Broad-scale magnetic anomalies over central and eastern Canada: a discussion

1981 ◽  
Vol 18 (3) ◽  
pp. 657-661 ◽  
Author(s):  
R. L. Coles ◽  
G. V. Haines ◽  
W. Hannaford
Keyword(s):  
Magnetic Field ◽  
Sea Level ◽  
Vertical Component ◽  
Magnetic Anomalies ◽  
Superior Province ◽  
The South ◽  
Earth’S Magnetic Field ◽  
Eastern Canada ◽  
Earth's Magnetic Field ◽  
Broad Scale

Profiles of anomalies in the vertical component of the Earth's magnetic field over central and eastern Canada, observed at an average altitude of 4 km above sea level, show broad regions with distinctive anomaly character. These subdivisions indicate major differences in the evolutions of regions within individual structural provinces. Particularly notable is a region of intense anomalies in the northern part of the Superior Province in Quebec, contrasting with much weaker anomaly relief to the south and east.

scholarly journals Palaeomagnetism of Eocene Talerua Member lavas on Hareøen, West Greenland

2005 ◽  
Vol 52 ◽  
pp. 27-38
Author(s):  
Anne G. Schmidt ◽  
Peter Riisager ◽  
Niels Abrahamsen ◽  
Janna Riisager ◽  
Asger Ken Pedersen ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Microprobe Analysis ◽  
Magnetic Polarity ◽  
Magnetic Field Direction ◽  
Vertical Profiles ◽  
The West ◽  
Volcanic Province ◽  
West Greenland ◽  
Maximum Duration ◽  
Good Accordance

The results of a palaeomagnetic sampling carried out along two vertical profiles (altogether 19 lavaflows, 126 samples) covering the entire stratigraphy of the Talerua Member lavas (~39 Myr old) that outcrop on the island Hareøen are presented and represent some of the youngest volcanism in the West Greenland flood volcanic province. Rock magnetic experiments and microprobe analysis demonstrate that the dominant magnetic mineral in all studied lavas is titanomagnetite that has experienced variable amounts of high temperature deuteric oxidation as well as low temperature hydro-thermal oxidation. Based on detailed demagnetization experiments, well-defined palaeomagnetic site-mean directions were isolated from all 19 lavas. The composite profile contains two magnetic polarity zones suggesting a maximum duration of Talerua Member volcanism of ~1.4 Ma. After grouping flows having the same remanent magnetic field direction, 13 individual readings of the palaeomagnetic fields were obtained. The palaeomagnetic pole with coordinates 76.3°N, 201.5°E (A95=7.4°, K=32.7, N=13) is in good accordance with palaeomagnetic poles from other continents rotated back to Greenland using plate kinematic rotation poles.

The tectonic relationship of two Early Proterozoic dyke swarms to the Kapuskasing Structural Zone: a paleomagnetic and petrographic study

1990 ◽  
Vol 27 (1) ◽  
pp. 87-103 ◽  
Author(s):  
H. C. Halls ◽  
H. C. Palmer
Keyword(s):  
Magnetic Polarity ◽  
Lower Grade ◽  
Northern Ontario ◽  
Early Proterozoic ◽  
Before And After ◽  
Normal Polarity ◽  
Main Period ◽  
Dyke Swarms ◽  
Host Rocks ◽  
Relationship Of

A tea-coloured cloudiness in groundmass feldspars characterizes dykes of two Early Proterozoic swarms (2.45 Ga Matachewan; 2.04 Ga Kapuskasing) that intrude amphibolite to granulite host rocks within the Kapuskasing Structural Zone (KSZ) of northern Ontario. Outside the KSZ the dykes occur in lower-grade terranes and contain unclouded feldspars. Matachewan dykes within the KSZ are also fresh, contain an aluminous, blue–green amphibole, have fewer plagioclase phenocrysts, and on average are thinner compared with their counterparts outside, which are more hydrously altered, contain a green, fibrous amphibole, and are locally abundant in felspar phenocrysts.Within the Matachewan swarm, magnetic polarity domains — areas of dominantly normal or reversed magnetization — have been identified; the boundaries of these domains correspond closely to major faults. Two of these faults form the boundaries of the KSZ and separate normal dykes within from dominantly reversed ones outside.The foregoing petrological and paleomagnetic observations are related to differential vertical crustal movements that have raised younger, normal-polarity Matachewan dykes (as exemplified by those within the KSZ) from a deeper crustal level and juxtaposed them against older, reversely magnetized dykes that were intruded at shallower crustal levels.Paleomagnetic baked-contact tests on Kapuskasing dykes suggest that they were intruded both before and after the main period of crustal uplift and tilting along the KSZ and that dykes within 4 km of the southeastern boundary fault were raised from depths where temperatures exceeded 580 °C, the Curie-point isotherm for magnetite.

Synopsis of paleomagnetic studies in the Kapuskasing structural zone

1994 ◽  
Vol 31 (7) ◽  
pp. 1206-1217 ◽  
Author(s):  
D. T. A. Symons ◽  
M. T. Lewchuk ◽  
D. J. Dunlop ◽  
V. Costanzo-Alvarez ◽  
H. C. Halls ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Fault Zone ◽  
Limited Area ◽  
The West ◽  
West Side ◽  
Thrust Faulting ◽  
Abitibi Subprovince ◽  
Normal Polarity ◽  
Slip Displacement ◽  
Radiometric Ages

This paper summarizes results from paleomagnetic studies sponsored by Lithoprobe on the Kapuskasing structural zone (KSZ). Data from Archean rocks outside the KSZ indicate that the Wawa Subprovince has not been significantly rotated or translated (< 5°) relative to the Abitibi Subprovince. Results from the granulites and amphibolites indicate that the KSZ underwent several kilometres of uplift at ca. 2.51 Ga and then 10 ± 5° west-northwest tilt with several kilometres of further uplift between 2.04 and 1.88 Ga from thrust faulting on the Ivanhoe Lake fault zone. Localized chemical remagnetization occurred at 1.1 Ga along the west side of the Shawmere anorthosite. Paleomagnetic data from the 2.45 Ga Matachewan diabase dike swarm indicate that it was emplaced within one reversed to normal polarity interval of less than 5 Ma. Their polarity pattern indicates major north-trending faults with several kilometres of dip-slip displacement. Their remanence confirms that the Superior Province was deformed around the KSZ into an oroclinal flexure with 40° changes in trend between 2.04 and 1.88 Ga. Results from eight 1.1 Ga alkali syenite–carbonatite complexes show that the KSZ and adjacent subprovinces have undergone only minor uplift (< 6 ± 2 km) since emplacement. Also, these data refine the radiometric ages of some complexes, demonstrate that the use of superchrons to correlate Keweenawan units in the Midcontinental Rift is unsound, and show that Keweenawan magnetic field was symmetrical. Many specific conclusions that relate to a given unit or limited area were drawn in the KSZ paleomagnetic studies.

Paleomagnetism and U–Pb geochronology of the Lac de Gras diabase dyke swarm, Slave Province, Canada: implications for relative drift of Slave and Superior provinces in the PaleoproterozoicGeological Survey of Canada Contribution 20080350.

2009 ◽  
Vol 46 (5) ◽  
pp. 361-379 ◽  
Author(s):  
Kenneth L. Buchan ◽  
Anthony N. LeCheminant ◽  
Otto van Breemen
Keyword(s):  
Magnetic Polarity ◽  
Canadian Shield ◽  
Dyke Swarm ◽  
Superior Province ◽  
Igneous Complex ◽  
Contact Test ◽  
Slave Province ◽  
Formed Part ◽  
Dyke Swarms

Lac de Gras diabase dykes trend north to NNE across the central Slave Province of the Canadian Shield. U–Pb baddeleyite ages of 2023 ± 2 and 2027 ± 4 Ma are interpreted as dyke emplacement ages. These ages are similar to that of the Booth River igneous complex, exposed along the margins of Kilohigok Basin near the northern end of the dyke swarm. Ten paleomagnetic sites (from four to six dykes) yield a mean paleopole at 11.8°N, 92.1°W (dm = 8.4°, dp = 6.0°). A positive baked contact test where a Lac de Gras dyke crosscuts a NE-trending Malley dyke demonstrates that this pole is primary. It represents the first key Paleoproterozoic pole from the Slave Province and, hence, the first Paleoproterozoic Slave pole suitable for reconstructing paleocontinents. Although a direct comparison is not available with precisely dated paleopoles of identical age from other Archean cratons, a comparison is made with a sequence of precisely dated poles from Superior Province dyke swarms, including those 40–50 million years older and 25 million years younger. It yields two options depending on the relative magnetic polarity assumed for data from the two cratons. The two cratons were either at similar latitudes, but not in their present relative orientations, when the swarms were emplaced, or separated in latitude by ∼40°–60°. In either case, they may have drifted separately or formed part of a single (super)continent that subsequently broke up with the two cratons drifting separately to attain their present configuration. Additional key paleopoles are required to distinguish between these interpretations.

scholarly journals Night-time Sferic Propagation at Frequencies Below 10 KHz

1967 ◽  
Vol 20 (1) ◽  
pp. 101 ◽  
Author(s):  
KJW Lynn ◽  
J Crouchley
Keyword(s):  
Magnetic Field ◽  
Geographic Distribution ◽  
Angle Of Incidence ◽  
European Studies ◽  
Earth’S Magnetic Field ◽  
Night Time ◽  
The West ◽  
Earth's Magnetic Field ◽  
Effective Angle

Results of a study at Brisbane of individual night-time sferics of known origin are described. A propagation attenuation minimum was observed in the 3-6 kHz range. The geographic distribution of sferic types was also examined. Apparent propagation asynunetries were observed, since sferics were detected at greater ranges to the west than to the east at 10 kHz, whilst the number of tweek-sferics arising from the east was about four times that arising from the west. Comparison with European studies suggest that these asymmetries are general. These results are then " interpreted in terms of an ionospheric reflection cgefficient which is a function of the effective angle of incidence of the wave on the ionosphere and of orientation with respect to the Earth's magnetic field within the ionosphere.

scholarly journals Kinematic partitioning in the Southern Andes (39° S–46° S) inferred from lineament analysis and reassessment of exhumation rates

2021 ◽  
Author(s):  
Paul Leon Göllner ◽  
Jan Oliver Eisermann ◽  
Catalina Balbis ◽  
Ivan A. Petrinovic ◽  
Ulrich Riller
Keyword(s):  
Fault Zone ◽  
Vertical Displacement ◽  
Strike Slip ◽  
Structural Studies ◽  
Southern Andes ◽  
Plate Convergence ◽  
Exhumation Rates ◽  
Lineament Analysis ◽  
Dextral Strike Slip ◽  
Data Call

AbstractThe Southern Andes are often viewed as a classic example for kinematic partitioning of oblique plate convergence into components of continental margin-parallel strike-slip and transverse shortening. In this regard, the Liquiñe-Ofqui Fault Zone, one of Earth’s most prominent intra-arc deformation zones, is believed to be the most important crustal discontinuity in the Southern Andes taking up margin-parallel dextral strike-slip. Recent structural studies, however, are at odds with this simple concept of kinematic partitioning, due to the presence of margin-oblique and a number of other margin-parallel intra-arc deformation zones. However, knowledge on the extent of such zones in the Southern Andes is still limited. Here, we document traces of prominent structural discontinuities (lineaments) from the Southern Andes between 39° S and 46° S. In combination with compiled low-temperature thermochronology data and interpolation of respective exhumation rates, we revisit the issue of kinematic partitioning in the Southern Andes. Exhumation rates are maximal in the central parts of the orogen and discontinuity traces, trending predominantly N–S, WNW–ESE and NE–SW, are distributed across the entire width of the orogen. Notably, discontinuities coincide spatially with large gradients in Neogene exhumation rates and separate crustal domains characterized by uniform exhumation. Collectively, these relationships point to significant components of vertical displacement on these discontinuities, in addition to horizontal displacements known from published structural studies. Our results agree with previously documented Neogene shortening in the Southern Andes and indicate orogen-scale transpression with maximal vertical extrusion of rocks in the center of the transpression zone. The lineament and thermochronology data call into question the traditional view of kinematic partitioning in the Southern Andes, in which deformation is focused on the Liquiñe-Ofqui Fault Zone.

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