The ferrodiorite zone, established by Allard (1976), was originally included as a subdivision of the « Layered Series » by Daigneault and Allard (1990). It is now designated as an informal lithodeme of the Lac Doré Layered Unit (Leclerc et al., 2017).

According to Leclerc et al. (2017, p. 23):

“The ferrodiorite zone consists of ferrodiorite, ferrogabbro and ferropyroxenite. Outcrops visited along Road 167, west of Caché Lake, expose dark grey, medium-grained ferrogabbro that is magnetic, brecciated and intruded by a grey to white pegmatite from the Chibougamau Pluton. A detailed study of the ferrodiorite zone by Baskin (1975) suggests the subdivision into subzones F1, F2 and F3. Ferrogabbros, ferropyroxenites, ferroperidotites and ferrodiorites of subzone F1 are grey to dark green, and display a cumulate structure, magmatic foliation and local rhythmic layering (Daignault and Allard, 1990). Subzone F2 consists of fine-grained plagioclase-pyroxene ferrodiorites and ferronorites, while subzone F3 is very similar to subzone F1 (Daigneault and Allard, 1990).”