Large scale magnetic anomalies over western Canada and the Arctic: a discussion

Coles, Richard; Haines, G. V.; Hannaford, W.

doi:10.1139/e76-082

Cited by 53 publications

(18 citation statements)

References 36 publications

(60 reference statements)

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“…On regional scale compilations, such as the magnetic anomaly map of North America (Geological Society of America, 1987), this anomaly is revealed as a large positive feature. Coles et al (1976) also confirmed the presence of this Magsat anomaly from high-level airborne data. They described it as a wide belt of intense anomalies that may be evidence for a Precambrian orogenic zone.…”

Section: Magnetic Anomaliessupporting

confidence: 73%

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Geohazard assessment from satellite magnetic data modeling—with examples from the Arctic Margin along the Canada Basin and the Korean Peninsula along 40°N (latitude) parallel

et al. 2008

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Long-wavelength, relative high-amplitude-magnetic anomalies obtained at satellite altitudes have provided an understanding of the nature of the deeper crust of the Earth. We have studied two such long-wavelength anomalies in regions of high stress-one with a large and one with a lower amplitude anomaly. The first feature is on the Canada Basin continental margin in the Northwest and Yukon Territories, Canada (magnetic anomaly range: 19 nT to −6 nT at 350-km altitude). This area is also the focus of significant stress and earthquake activity. We interpret this anomaly and associated tectonic activity with this region's position at or near the fulcrum of the scissors-like opening of the Canada Basin in the mid-Mesozoic Era. The second is a section along the 40• N (latitude) parallel crossing the Korean Peninsula (magnetic anomaly range: <−2 nT to >3 nT at 350-km altitude), where an east-west fracture zone has been proposed to extend from northeastern China, across the Korean Peninsula, Sea of Japan and (Northern) Japan.

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Section: Magnetic Anomaliessupporting

confidence: 73%

“…They described it as a wide belt of intense anomalies that may be evidence for a Precambrian orogenic zone. Coles et al (1976) further suggested that the crystalline continental basement (Fig. 3, Interior Platform) extends far to the west beyond the exposed and known buried shield.…”

Section: Magnetic Anomaliesmentioning

confidence: 95%

Geohazard assessment from satellite magnetic data modeling—with examples from the Arctic Margin along the Canada Basin and the Korean Peninsula along 40°N (latitude) parallel

et al. 2008

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“…They unconformably overlie and intrude rocks deformed and metamorphosed during the Calderian orogeny . The zone can be traced along strike for an additional 500 km southward beneath a thin veneer of Paleozoic cover and to the north bends westward then continues for another 300 km (Coles et al, 1976;Hildebrand and Bowring, 1984;Hoffman, 1987;Hildebrand et al, 2010). Thus, its two-dimensional extent is comparable to modern continental arc terranes.…”

Section: Great Bear Magmatic Zonementioning

confidence: 90%

The nature of volcano-plutonic relations and the shapes of epizonal plutons of continental arcs as revealed in the Great Bear magmatic zone, northwestern Canada

et al. 2010

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The shapes of plutons and their emplacement mechanisms, the connection between the volcanic and plutonic realms, and the development of batholiths have been of interest to geologists since they realized that plutons were once low viscosity magma. These issues have proven diffi cult to resolve because there are few places that have enough relief to expose the critical relations. The Great Bear magmatic zone, a Paleoproterozoic continental arc located in northern Canada's Wopmay orogen, provides an informative fi eld setting to resolve some of these issues because the rocks are generally non-metamorphosed and were broadly folded such that calderas, stratovolcanoes, and a wide variety of plutons are exposed in oblique cross-section on fold limbs in an area of subdued topographic relief.Early mafi c plutons intruded co-magmatic pillow basalt piles as thin sheets with aspect ratios of 10-15. Plutons of intermediate composition, temporally associated with andesitic stratocones, have fl at or slightly domical roofs and fl at fl oors, and aspect ratios in the range of 5-10. Granodioritic to monzodioritic plutons that cut thick sequences of ashfl ow tuff and related volcaniclastic rocks are generally sheet-like bodies with aspect ratios of 10-20, except where they intrude calderas and form resurgent plutons. Granitic plutons intrude at slightly deeper crustal levels, are generally younger, and typically have miarolytic cavities, pegmatites, and associated dike swarms. The granites have fl at roofs and fl oors but generally have lower aspect ratios than the intermediate composition plutons.Cycles-where magma bodies were fi rst partially evacuated by eruption, then were re-energized and rose into their own ejecta to form plutons-span the compositional range from basalt to rhyodacite. The cycle of eruption, with the partial evacuation of chambers and subsequent rise of remaining magma to even higher levels in the crust explains why it is generally so diffi cult to link volcanic eruptions to specifi c plutons.The overall development of the Great Bear magmatic zone-from small-scale local eruptions of basalt to voluminous eruptions of intermediate composition ash-fl ow tuff followed by wide-scale emplacement of granitic plutons-is interpreted to represent input of subduction-related magmas, which led to progressive heating, melting, and wholesale upward differentiation of the crust beneath the arc.

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“…Geological interpretations of the data shown in Fig. 3 are given in Haines et al (1971) and Coles et al (1976Coles et al ( , 1981. The data have been reduced to magnetic anomalies using the appropriate Definitive Geomagnetic Reference Field (DGRF) (Langel 1992), which provide an improved regional field representaCan.…”

Section: Earth Physics Branch Datamentioning

confidence: 99%

An assessment of long-wavelength magnetic anomalies over Canada

Pilkington¹,

Roest²

1996

Can. J. Earth Sci.

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The reliability of the long-wavelength portion (>300 km) of the magnetic field over Canada, as represented by the national aeromagnetic anomaly database compiled by the Geological Survey of Canada (GSC), is assessed by comparison with two independent data sets: a high-altitude country-wide survey carried out by the former Earth Physics Branch (EPB) and data from the MAGSAT and POGO satellite missions. The different altitudes at which each data set was measured (300 m, -4 km, and -400 km), and their different resolution and time span of observations allow a determination of the integrity of selected wavelength bands in each data set. The (upward-continued) EPB and MAGSAT-POGO fields compare well for wavelengths of 300-2500 km. 'The GSC data show significant differences to the former, indicating that the levelling and merging of several hundred individual surveys has degraded the longer wavelength components of the magnetic field. Replacing the GSC wavelength components >300 km with those from the EPB field produces a magnetic data set containing more dependable information within the largest possible waveband.RCsumC : La fiabilitC de la portion de l'onde longue (>300 krn) du champ magnktique au-dessus du Canada, telle que reprCsent& par la base de donnCes des anomalies a6romagnCtiques nationalcs qui a Ct C compilCe par la Commission gblogique du Canada, est test& par la confrontation de deux groupes de dnnnCes indtpendantes : soit la comparaison d'un lev6 de haute-altitude, couvrant le pays d'un bout ? i l'autre, effectuC par l'ancienne Direction de la physique du globe, avec les donn&s enregistrees par satellites des deux missions MAGSAT et POGO. Les altitudes diffkrentes des enregistrements des donnks ont Ct C rnesurtes (300 m, -4 km et -400 kml, et leur limite de rCsolution distincte, couplCe B la durCe des observations, autorisent une intCgralitC des bandes de longueur d'ondes sClectionnCes pour chaque groupe de donnCes. La comparaison indique un accord raisonnable entre les donnCes des champs (continus en altitude croissante), pour les longueurs d'ondes de 300 B 2500 km, qui ont Ct C obrenues par la Direction de la physique du globe et par les missions MAGSAT-POGO. Les donn&s des registres de la Commission gCologique du Canada contrastent avec celles de l'ancien levC, ce qui implique que le nivellement et le fusionnement de plusieurs centaines de lev& individuels altkrent les paramktres de la longueur d'onde maximale du champ magnCtique. La substitution des paramktres des longueurs d'ondes >300 km du registre de la Commission gblogique du Canada, par ceux du champ du registre de la Direction de la physique du globe, procure un ensemble dr donnCes magnCtiques traduisant une information qui est plus dCpendante sur la plus large gamme d'ondes possible. [Traduit par la rCdaction]

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Large scale magnetic anomalies over western Canada and the Arctic: a discussion

Cited by 53 publications

References 36 publications

Geohazard assessment from satellite magnetic data modeling—with examples from the Arctic Margin along the Canada Basin and the Korean Peninsula along 40°N (latitude) parallel

Geohazard assessment from satellite magnetic data modeling—with examples from the Arctic Margin along the Canada Basin and the Korean Peninsula along 40°N (latitude) parallel

The nature of volcano-plutonic relations and the shapes of epizonal plutons of continental arcs as revealed in the Great Bear magmatic zone, northwestern Canada

An assessment of long-wavelength magnetic anomalies over Canada

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