Eeyou Istchee James Bay: Deciphering its Secrets

Antimony is a strategic metal in very high demand. The Fortin Zone is located on the Wabamisk Property in the Eeyou Istchee James Bay region of Québec. The project covers a regional-scale antimony-arsenic lake sediment anomaly. Optioned in 2005 to a mining company, this 51-km-long project came back fully under Azimut's control in 2022.

Prospecting work on Wabamisk in 2024 led to the discovery of outcrops with grades of up to 24.8% Sb and 1.34 g/t Au. Since then, 86 core holes (12,286 m) have been drilled to define the zone. A major additional drilling campaign is planned for 2026.

Fortin is an antimony-gold mineralized system associated with a stratiform albitic unit and its sheared contacts. It is recognized over a length of at least 1.8 km to a minimum vertical depth of 250 m. Trending E-W and dipping steeply to the south, the mineralized zone varies in thickness from 5 to 50 m. Significant results include:

- 2.08% Sb, 2.64 g/t Au over 17 m, including 3.15% Sb, 10.92 g/t Au over 4.0 m (channel); and

- 1.10% Sb, 0.38 g/t Au over 51.5 m, including 3.43% Sb, 2.37 g/t Au over 6.50 m (drilling).

The Fortin Zone is hosted by Archean metasedimentary rocks of the Opinaca Subprovince, close to the lithostructural boundary with the La Grande Subprovince. The albite unit is interpreted as epigenetic, resulting from a huge sodic hydrothermal discharge in a permeable metawacke layer.

The Troilus deposit (13.01 Moz AuEq) is located in the Frotet-Evans greenstone belt. Although this mineralization was historically mined by open pit from 1996 to 2010, producing more than 2 Moz Au and 70 kt Cu, the nature of the deposit remains controversial. It was originally described as a porphyry-type mineralization hosted in volcanic rocks, before being interpreted as the result of superimposed orogenic events. This controversy is a direct consequence of the fact that the deposit has characteristics typical of several types of mineralization (VMS, porphyry, epithermal and orogenic). After sustained exploration efforts and ~350,000 m of drilling since 2018, a reclassification is required. We propose a polyphase origin dominated by a synvolcanic episode. A multidisciplinary approach shows the importance of the early mineralizing event active during the emplacement of the polyphase Troilus intrusion (~2791 Ma) and a swarm of porphyritic felsic dykes (~2786 Ma) in a submarine caldera context. Au-Cu-Ag (Mo-Zn) mineralization is mainly disseminated, in the form of a stockwerk of veinlets, semi-massive to massive sulphides and mineralized breccias located in specific stratigraphic units. The mineralization is associated with sodic, potassic, calc-silicate/propylitic and clay alteration, and is commonly associated with magnetite. The deposit has been deformed and metamorphosed to amphibolite facies, resulting in significant remobilization and strong structural control in a dextral transpression system associated with the formation of locally mineralized quartz veins.

The Lake Caulincourt area, in Eeyou Istchee James Bay (NTS 33A03 and 33A06), located about one hundred kilometres north of Lake Mistassini, was the subject of a geological mapping campaign at a 1:50,000 scale by the MRNF during the summer of 2024. This area is characterized by the presence of a large volume of metasedimentary rocks belonging to the Opinaca (north) and La Grande (south) subprovinces. The work carried out has repositioned the contact between these two subprovinces on the basis of new structural and metamorphic observations, allowing a more rigorous distinction to be made between the metasedimentary rocks of the Laguiche Complex (Opinaca) and those of the Prosper Formation (La Grande).

This work also defined two new sequences of volcano-sedimentary rocks: 1) the Caulincourt Formation in the southern part of sheet 33A06, where it forms bands parallel to the Opinaca-La Grande contact in the Prosper Formation; and 2) the Clauzel Group located within the Prosper Formation, in the centre of sheet 33A03. These new volcano-sedimentary bands offer interesting mineral potential due to the presence of zones strongly mineralized in sulphides (Py-Cp-Po) in both sectors.

The geological survey of the Lake Chamic area covers NTS sheets 32P11 and 32P14. Units in the NE part of the area represent the western extension of the plutons and gneisses of the Maingault Complex and the granulitic volcano-sedimentary rocks of the Mistamiquechamic Formation. These packages are injected with mafic-ultramafic intrusions from the Chamic Suite.

Rocks in the north-western and central parts of the area form the eastern extension of the Lac des Montagnes Belt (LMB), which consists of a metasedimentary package assigned to the Voirdye Formation. This sequence was partly deposited on the kilometric metavolcanic units of the Tichégami Group that form the heart of the area. Late mafic-ultramafic intrusions of the Nasacauso Suite and white pegmatite of the Senay Suite are injected into the Voirdye and Tichegami. The latter lies in structural contact with the plutonic and gneissic rocks of the Hutte and Théodat complexes, which are interpreted as the basement of the supracrustal rocks.

The southern part of the area is formed by the Opatica Subprovince, which is a plutono-gneissic package containing grooves of metavolcanites from the Michaux Group.

The area has a number of mineralizations:

- polymetallic volcanogenic massive sulphides;

- synvolcanic gold-bearing quartz-sulphides veins;

- base metals associated with metasomatic alteration zones;

- exhalative sulphides hosted in sedimentary rocks;

- gold-bearing associated with quartz pebble conglomerates;

- stratiform gold-bearing in banded iron formations;

- magmatic nickel-copper;

- lithium-caesium-tantalum associated with pegmatites.

The Whabouchi lithium deposit has proven reserves of 10.5 Mt at 1.40% LiO₂, making it one of the largest mineralizations of this type in Québec and Canada. Spodumene and petalite are the main lithiniferous minerals and help to distinguish mineralized aplite-pegmatite intrusions from waste rock. These granitic dykes cut a rock package consisting of basalt, gabbro, quartzofeldspathic porphyry (QFP), granodiorite and tonalite that were variably deformed during phase D1-D2 along the River Nemiscau Shear Zone (ZCrn), a NE-SW sinistral structure dipping to the SE. Locally visible leucosomes indicate that the aplite-pegmatite dykes are mainly the result of partial melting of a sedimentary source and were emplaced along the ZCrn. These are NE-trending syn-D2 dykes that dip steeply (~80°) to the SE and are generally located between basalts exhibiting the S1/S2/L2 fabric and gabbros and/or sheeted QFPs hosting the S2/L2 fabric. The package shows both subvertical and subhorizontal stretching, illustrated by a boudinage of the foliation and dykes that are mainly symmetrical in both directions along the ZCrn. Rare kinematic indicators, as well as a strong L2 lineation dipping ~70° to the SSW defined by spodumene crystals and stretched quartzofeldspathic aggregates, show that the Whabouchi lithium deposit was emplaced in the vertical extrusion zone of a NNE-verging sinistral transpression system.

The Lion deposit is located about 55 km east of the Cree community of Nemaska, James Bay, Quebec. This deposit is part of a 212 km² that covers approximately 50 km of prospective stratigraphy. The mineralization consists mainly of chalcopyrite-cubanite +/- pentlandite and is associated with a large ultramafic cumulates sequence (the Caumont Suite).

89 diamond drill holes totaling 35,558 meters (2023-2025) have outlined a northeast to southwest striking zone that is 290 meters along strike, 18 to 50 meters average width to a vertical depth of 650 meters. The mineralized zone plunges 67 degrees to the northwest.

Two seasons of field mapping (2024-2025) at the Lion ultramafic-hosted polymetallic deposit (Cu-Ni-Pd-Pt-Ag-Au) have revealed that the ultramafic layered unit from the Caumont Suite is actually older than the surrounding Voirdye Formation metasediments and the Champion Complex tonalitic gneiss. This relationship is crucial in understanding the timing of the mineralization. The metasediments from the Voirdye Formation at the contact with the dunite contains beds and cross-bedded laminations of detrital chromite, which suggests that the dunite underwent an erosional event. The tonalite from the Champion Complex, locally contains xenoliths of the ultramafic unit, suggesting that the ultramafic unit is actually older than the tonalite intrusive.