Potential-field signatures of buried Precambrian basement in the Western Canada Sedimentary Basin

Abstract

An internally consistent, levelled compilation of magnetic data is derived for Alberta and northeastern British Columbia. With Bouguer gravity data, this compilation is used to refine the definition of Precambrian basement domains within the Western Canada Sedimentary Basin. Magnetic data are draped at a constant distance above the mapped basement surface to reduce the effects of varying magnetic source depths. Automated interpretation methods that effectively map outlines of magnetic sources are used to characterize the internal structure of the domains and to aid in their delineation. The basement domain map thus derived differs from previous interpretations in the extension of domains further to the southwest, due mainly to the availability of new public-domain magnetic data and the more precise definition of domain boundaries, based on the magnetic source location maps. The Nahanni, Hottah, Chinchaga, Thorsby, Vulcan, and Kiskatinaw domains are weakly magnetic and characterized by magnetic sources that are paramagnetic, comprising low-susceptibility silicate minerals. All other domains are characterized by the presence of ferrimagnetic material, most likely magnetite, which has a sufficiently high susceptibility to produce measurable anomalies. The largest anomalies and magnetizations are found in the Fort Nelson, Fort Simpson, Buffalo Head, Talston, Ksituan, and Matzhiwin domains. Such large magnetizations are usually indicative of intermediate igneous rocks associated with magmatic arc environments. Moderate-amplitude anomalies and (or) magnetizations are characteristic of the Nova, Wabamun, Lacombe, Rimbey, Loverna, and Medicine Hat domains, suggesting the presence of ferrimagnetic basic and granitoid rocks. Within some of the moderately magnetic domains are areas of paramagnetic lithologies that produce no magnetic anomalies. The narrower regions of magnetic lows, such as the Thorsby, Kiskatinaw, and Vulcan domains, are interpreted as resulting from demagnetization effects accompanying collision. Since demagnetization zones are limited in areal extent, the wider, more extensive magnetic lows of the Chinchaga and Hottah domains likely result from a combination of boundary demagnetization and a lower bulk magnetization level of crustal lithologies present.

A Paleoproterozoic Andean-type iron oxide copper-gold environment, the Great Bear magmatic zone, Northwest Canada

“…1850 Ma, in the form of northeast-striking transcurrent faults that dextrally offset all rocks older than the Cleaver mafic dyke swarm (Hildebrand et al, 1987;Hayward and Corriveau, 2015). These faults are part of the large-scale McDonald fault system to the south, which can be traced for ~500 km in the subsurface of the Phanerozoic platform, from Great Slave Lake to the foothills of the Rocky Mountains (Pilkington et al, 2000;Aspler et al, 2003).…”

Chronostratigraphy of the Hottah terrane and Great Bear magmatic zone of Wopmay Orogen, Canada, and exploration of a terrane translation model

“…Late-stage, northeast-striking, brittle-dextral faulting, such as the dextral McDonald Fault, continued to the Cordilleran thrust front ( Fig. 1A; Pilkington et al 2000;Aspler et al 2003;Hayward and Corriveau 2014), and therefore brittle deformation post-dated arrival of the Nahanni terrane (cf. Hayward and Corriveau 2014).…”

Basement Tectonics and Fault Reactivation in Alberta Based on Seismic and Potential Field Data

“…Modelling and interpretation of regional gravity and magnetic data can provide valuable insights for understanding crustal structure beneath sedimentary basins [8,9] including constraints for understanding geological risk factors for induced seismicity [10]. Models derived from magnetic and gravity data, due to their non-uniqueness, are usually combined with other geological and geophysical information (e.g.…”