Archean basement underlying Paleoproterozoic Cape Smith Belt: part of Povungnituk map area NTS 35-C

Field work for this report was done in 1985 as part of a project that was intended to clarify the relationship of the Cape Smith Belt to its encompassing tectonic setting. Accordingly, a strip of 1 degree longitude width (approximately 105 km) was to be mapped from south of the Cape Smith Belt to the coast of Hudson Strait. Due to unfortunate circumstances only one summer's field work was completed when the project was cancelled. A preliminary map and report of the work completed that summer with few details was published earlier (Baragar et al., 1986). The present map represents that portion of the summer's field work that lies south of the Cape Smith Belt. Work done on the north side of the Belt is represented in a separate report and map; the Kovik Bay Map Area 35F (Baragar, 2015). A summary map of the area is shown in Fig. 1 as well as in the 1:250 000 scale geology map (accompanying pdf) where northward Archean trends can be seen to be truncated by rocks of the east-northeastward trending Paleoproterozoic Cape Smith Belt. Within this area most of the contact between the stratified rocks of the Cape Smith Belt and underlying Archean basement is clearly unconformable (Baragar et al. 2001). In places it is obscured or replaced by south-verging thrust faults that roughly parallel the trend of the belt. In this report only the geology of the Archean rocks will be addressed in detail. The geology of the Cape Smith Belt immediately to the north is covered in such publications as: Baragar and Scoates, 1987; Moorehead, 1988; Picard, 1989; and Baragar et al., 2001. The Archean geology has been subdivided into four units but as shown in the legend of Fig.1 probably only two of them are to be regarded as primary lithologies; the trondhjemite-tonalite and the megacrystic granite gneisses. Gneisses of the mafic margins and of the migmatites seem to be, at least in part, phases of the megacrystic granite gneisses. The trondhjemite-tonalite unit is interpreted as being the older but relationships between the various units are not well defined and the interpretation depends on less direct evidence and, to a degree, intuition. This will be discussed further in the descriptions of units that follow. Cross cutting the Archean gneissosity and widely distributed within the map area (Fig.1 and accompanying pdf) are two sets of dolerite dykes, of probable Proterozoic age, trending respectively, northward and westward. For most of the dykes, relatively short lengths were all that were observed but in each set at least one major dyke exists that can be traced through a number of traverse intersections and on air photographs for distances of 22 km (northward set) and 9 km (westward set) respectively.

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