The Jean-Marie Intrusive Suite was defined during mapping by Moukhsil and El Bourki (2021) ~65 km NW of Lake Saint-Jean. This unit consists of several phases distributed in an intrusion well circumscribed from the aeromagnetic survey (Intissar and Benahmed, 2015).

Hypersthene quartz syenite varies in colour from one outcrop to another. It is whitish, pinkish, black or grey in altered patina and pink-beige in fresh exposure. The rock is coarse grained to locally porphyraceous and foliated. In the field, the orthopyroxene content varies from 5% to 8% and is associated with biotite, magnetite and clinopyroxene. In thin sections, the following minerals are also recognizable: polygonal quartz having undulatory extinction, K-feldspar phenocrystals, perthitic or not, plagioclase locally with myrmekitic symplectite, hornblende and some crystals of allanite. Accessory minerals are zircon and apatite.

Gabbronorite is grey-black in altered patina and fresh exposure. The rock is ophitic and medium to coarse grained. Gabbronorite contains ~1% leuconorite clusters white-grey in fresh or altered surfaces and medium to coarse-grained. Leuconorite clusters are 20 cm to 80 cm in diameter and display diffuse contact with gabbronorite, indicating their cogenetic character. A few outcrops of fine to medium-grained gabbro have been mapped among gabbronorite, and gabbro mainly occurs as centimetric dykes.

Gabbronorite contains orthopyroxene, altered clinopyroxene (augite), green hornblende, biotite, apatite and opaque minerals (magnetite, pyrite). Leuconorite clusters contain plagioclase and orthopyroxene. Both lithologies have magmatic textures and are intruded by charnockite of the same suite. Locally, gabbronorite intrudes charnockite. This seems to indicate the cogenetic character, without mixing, of the two magmas (gabbronoritic and granitic) emplaced at medium and high pressure (presence of magmatic orthopyroxene in both lithologies).

Gabbronorite and gabbro layers in this unit may contain Fe-Ti oxides with some phosphorus and vanadium. They mainly contain hemo-ilmenite 1 mm to 1.5 mm in size. Geochemical analysis returned contents of up to 31.20% Fe₂O₃ and 5.73% TiO₂ (analysis 2020079554). Oxide-enriched gabbronorite can be classified as OAGN (OAGN = Oxide-Apatite-Gabbronorite, acronym proposed by Dymeck and Owens, 2001) with or without apatite. The texture of OAGN is granular. It contains hemo-ilmenite disseminated or concentrated in bands and millimetric to centimetric layers. Bands are then composed of plagioclase, pyroxenes, biotite, hornblende, hemo-ilmenite, ilmenite, magnetite and some apatite.

Thickness and distribution

The Jean-Marie Intrusive Suite consists of a multiphase intrusion mapped in the NW part of sheet 32H02. Interpretation of aeromagnetic maps has allowed extending it to the west (sheet 32H03) and to the north (sheets 32H06 and 32H07). This interpretation gives it an elliptical shape with a long axis of 30 km, oriented N-S, and a short axis of ~7 km oriented E-W.

Dating

None.