Definition of magnetic domains within the Rae Craton, mainland Canadian Shield, Nunavut, Northwest Territories, Saskatchewan, and Alberta: their magnetic signatures and relationship to geology
Authors: Thomas M D 
Published: March 2018

The Archean Rae craton, western Churchill Province, occupies a huge area within the northwestern mainland Canadian Shield. It extends &amp;gt;1600 km from the Talston magmatic zone northeastward to the east coast of Melville Peninsula, ranging in width from
roughly 300 km to 900 km. The craton is covered by aeromagnetic data collected over many decades by Canada's National Aeromagnetic Survey Program, typically along lines 805 m apart at a flight elevation of 305 m. Additionally, many higher resolution aeromagnetic surveys have been completed during
the last decade or so. The craton is geologically mapped at various scales, but most geological coverage is at a relatively large scale. For this reason magnetic data provided by the national program are considered to be of sufficient resolution to investigate relationships with geology.
Here, seventy-five magnetic domains are defined using textures, fabrics, patterns, orientations and intensities of residual total magnetic field anomalies and their derivative equivalents (first vertical derivative, tilt angle). Given that patterns and orientations of narrow derivative magnetic
anomalies reflect closely geological structure, the magnetic domains can be viewed essentially as representative of structural domains. The maximum dimension of most domains is &amp;gt;100 km, but many attain dimensions of several 100 km. Although the Rae craton has an overall northeastward
trend, a strong pattern of linear magnetic domains running parallel to this trend along the length of the craton is not apparent. A few generally relatively broad and parallel domains do run northeastward along the spine of the craton between roughly the Talston magmatic zone and Aberdeen sub-basin.
Several narrower and typically less extensive domains also trend northeast within the Chesterfield block along the southeast margin of the craton southeast of the sub-basin. Where the southern part of the craton, south of the roughly east- trending Amer and Wager Bay shear zones, swings into a more
eastward trend, linearity is lost and domains become smaller and more irregular in shape, with some trending across the craton.
The best developed linear pattern of domains probably lies between the Thelon magmatic zone and Chantrey fault zone, where several narrow to moderately wide, sub-parallel domains extend between the McDonald fault (and its northeastward projection) and Queen Maud Gulf. Eastward they change
orientation progressively from northward to roughly N30°E towards the fault zone. A sense of a linear arrangement of domains is observed also on the Boothia and Melville peninsulas, with trends varying between approximately east-northeast and northeast. A broad area east of the Chantrey fault
zone, north of the Amer and Wager Bay shear zones, south of the Boothia Peninsula and including the southern part of the Melville Peninsula contains some linear domains trending approximately northeast, but there are also sizable domains of irregular shape lacking an internal magnetic fabric
characterized by prominent northeast trends.
Many close correlations between magnetic anomalies and mapped lithological units exist, but there are numerous examples where anomalies transect unit boundaries thus questioning boundary positions. Magnetic anomalies indicate probable lithological/compositional changes within many large gneissic
units pointing to a need for more detailed mapping. Many examples of exceptionally strong magnetic highs are associated with mapped iron formations. Such highs in areas apparently lacking iron formations signify their potential presence. Magnetic patterns and signatures outline locations of small
circular to roughly oval, unmapped igneous intrusions, and many faults not displayed on geological maps.