The Sigma-Lamaque Complex is located in the Val-d'Or area of the Province of Québec. The Precambrian rocks of the Canadian Shield, which underlie 90% of Québec including the Val-d'Or area, occupy a vast territory of 1,540,000 square kilometres that is renowned world-wide for its mineral resources and mineral industry. Exploration and mining in the area includes production of precious metals, base metals, ferrous metals and others, as well as industrial minerals (asbestos, ilmenite, dolomite, salt, graphite etc.), building materials and peat.

The Sigma-Lamaque Complex is the largest of a group of shear-zone related quartz tourmaline vein deposits occurring north of the Cadillac Tectonic Zone. The deposit consists of an extensive vein network hosted by andesitic flows and volcaniclastic rocks, intruded by an irregular mass of subvolcanic porphyritic diorite. A swarm of high-level feldspar porphyry dykes, striking east-west and dipping steeply to the south, overprints both rock types, and is in turn locally cut by steeply plunging non-porphyritic diorite tonalite stocks, with which mineralized veins are associated.

Mineralogical assemblages for the major lithologic units indicate that greenschist facies metamorphism was attained during various stages of regional deformation with the amphibole facies attained at the lowest levels of the underground mine. All intrusive rocks are overprinted by conjugate reverse oblique shear zones, striking east-west and dipping moderately to steeply north or south, with which mineralized veins are associated.