The Deloro Stock intrudes sediments and volcanics of the Grenville and Hastings Groups within the Grenville Structural Province near its southern boundary with overlying Palaeozoic sediments, which partly cover it. The stock is principally composed of a massive, red peralkaline granite grading to syenite and followed by a small intrusion of leucocratic granophyric granite. The massive granite consists principally of quartz, perthite, some albite, riebeckite-crossite, biotite, magnetite and accessories. This is the hypersolvus granite illustrated by Tuttle and Bowen (1958, Plate 2) as the Madoc granite. A zone of aenigmatite-bearing granite 100-200 m wide lies along the western margin. A peralkaline granite is shown at Moira Lake east-southeast of the Deloro Stock by Davidson et al. (1979, Fig. 19.4) but no details are given.