Previously referred to as lithological unit I1B in the Ministère’s compilation maps (MNRF, 2010a, b), this small intrusion was recently formally named the Kamadjideweckode Stock after nearby stream and lake (Guemache, 2020). Rocks that make up this stock do not outcrop, because they are hidden by a thick quaternary sequence, but diamond and sonic drilling revealed its nature, whereas aeromagnetic data (Keating et al., 2010; Keating and d’Amours, 2010) revealed its geometry.

The Kamadjideweckode Stock contains a granitic central area marked by low residual magnetic field intensity (nAkad1) and a higher intensity edge area of biotite quartz monzodiorite in the eastern part of the intrusion (nAkad2). The northern and southern edges of the intrusion are affected by an overall E-W tectonic foliation; it is dipping northward to the north and southward to the south. Some magnetic lineaments cut the stock and surrounding rocks along N-S, NE-SW and NW-SE directions (Beaudry, 1988). A NW-SE lineament in the extension of a shear crossed by drilling IM88-05 (Beaudry, 1988) could be a segment of the Harricana Shear Zone.

The two diamond drillings IM88-06 and IM88-07 (Beaudry, 1988) performed in the central area (nAkad1) indicate that the dominant lithology is a massive medium-grained granite.

Kamadjideweckode Stock 2 (nAkad2): Biotite Quartz Monzodiorite

Sonic drilling RO-463 provided insight into the lithology of the edge area (nAkad2), previously considered a contact metamorphism aureole affecting intermediate to mafic volcanic rocks of the Vanier-Dalet-Poirier Group (Beaudry, 1988). It consists of biotite quartz monzodiorite, leucocratic beige, massive, homogeneous and medium grained (Guemache, 2020). Black minerals are scarce (<10%). In thin sections, it contains quartz having undulatory extinction in places, slightly sericitized plagioclase, microperthitic microcline, commonly chloritized biotite, muscovite and, as accessory phases, titanite, epidote and opaque minerals such as magnetite. Calcite can account for up to 2% of the total volume of the rock.

Thickness and distribution

The Kamadjideweckode Stock is a small, almost circular intrusion (4 km x 3 km) located in the NW corner of sheet 32F04.

Dating

None.