Almost 90% of Québec’s bedrock is composed of Precambrian rocks belonging to the Canadian Shield (north of the Saint Lawrence River).
The remainder consists essentially of Paleozoic rocks: the St. Lawrence Platform surrounding the Saint Lawrence River and the Appalachians to the south of the river. These geological environments offer significant discovery potential for mineral deposits.
Québec is divided into seven main geological provinces: Superior, Nain, Churchill, Grenville, Appalachian, St. Lawrence Platform and Hudson Bay Platform. These are illustrated on map The Great Geological Domains of Québec .
The Superior Province (4.3 to 2.5 billion years [Ga]) occupies a large part of the North American continent and also covers half of Québec, for a total surface area of 750,000 km2. It is known around the world for its numerous gold, copper, zinc, nickel and silver deposits. More recently, important diamond deposits were discovered in kimberlites. The Superior Province is subdivided into a dozen subprovinces, half of them in Québec. The most well known is the Abitibi Subprovince, which is also the most extensive Archean volcano-sedimentary belt in the world, and famous for its gold, copper, zinc and silver deposits.
The Nain Province (3.8 to 1.3 Ga) is found mostly in Labrador, with only a small portion (about 60 km2) extending into the Torngat Mountains of Québec. It is composed of Archean metamorphic rocks.
The Churchill Province (2.9 to 1.1 Ga) covers an area of about 200,000 km2 in the northern part of Québec, to the north and northeast of the Superior Province. It is characterized by four distinct geological zones:
- the Ungava Orogen (Ungava Trough), known for its nickel-copper deposits;
- the New Québec Orogen (Labrador Trough), which hosts massive iron deposits as well as many copper, nickel and platinum group element (PGE) deposits;
- the Core Zone (formerly known as the Rae Province), located between the Labrador Trough and the Torngat Orogen, is composed of Archean and Paleoproterozoic rocks (2.9 to 1.75 Ga) as well as Mesoproterozoic plutonic rocks (1.7 to 1.1 Ga);
- the Torngat Orogen (2.1 to 1.75 Ga), located east of the Core Zone, where rocks are injected by kimberlites with diamond potential.
The Grenville Province (2.7 Ga to 600 million years [Ma]) covers an area of 600,000 km2. It forms the southeast limit of the Superior Province and is divided into two parts: the parautochthonous and allochthonous belts. The Grenville Province is known for its iron and ilmenite mines and for its industrial mineral potential.
The Appalachian Province (600 to 300 Ma) developed along the edge of the Canadian Shield during the Paleozoic, and covers an area of roughly 80,000 km2. It is divided into three distinct zones: 1) the Humber Zone, 2) the Dunnage Zone, and 3) the Gaspé Belt. It is bounded to the east by the Permo-carboniferous Magdalen Basin. In Québec, the Appalachians were affected by two main tectonic events: the Taconian and Acadian orogenies. The Mines Gaspé copper deposits are found in this geological province.
The St. Lawrence Platform (570 to 430 Ma) developed at the end of the Proterozoic and during the Paleozoic, with the formation of the Saint Lawrence rift. It covers an area of more than 30,000 km2 and overlies rocks of the Grenville Province. It is divided into two distinct platforms: the St. Lawrence Lowlands Platform and the Anticosti Platform. The main resource is limestone. Two carbonatite intrusions, Saint-Honoré (Grenville Province) and Oka (St. Lawrence Platform), host niobium deposits. Québec is the world’s second-largest producer of this rare metal.
The Hudson Bay Platform (450 to 410 Ma) covers an area of roughly 5,500 km2 in Québec just south of James Bay. It is composed of Paleozoic sedimentary rocks with a similar composition to those found in the St. Lawrence Platform.