Geology

Côté Gold is located in the Swayze greenstone belt in the southwestern extension of the Abitibi greenstone belt of the Superior Province. Igneous lithologies predominate and include both volcanic and plutonic rocks. Sedimentary rocks occur mainly near the top of the succession.

The Chester Intrusive Complex

The Chester Intrusive Complex (CIC), a crudely stratified tonalite–diorite laccolith containing numerous inclusions of mafic volcanic rocks, is host to the Côté Gold deposit. The CIC units formed from the crystallization of a number of pulses of several distinct and evolving dioritic and tonalitic magmas that display complex crosscutting relationships.

The intrusive phases were followed by magmatic-hydrothermal brecciation and the emplacement of several stages of gold-bearing veins. Subsequently, the deposit was intruded by several types of crosscutting dykes and was subjected to deformation, resulting in structural deformation zones and brittle faulting.

Deposit Details

The Côté Gold deposit is an Archean-aged, low-grade, bulk-tonnage gold (± copper) discovery. It is described as a synvolcanic intrusion-related, stockwork to disseminated gold deposit. Deposits of this type are commonly spatially associated with and/or hosted in intrusive rocks. They include porphyry Cu–Au, syenite-associated disseminated gold, and reduced Au–Bi–Te–W intrusion-related deposits.

Certain features of the Côté Gold deposit appear to resemble characteristics of gold-rich porphyry deposits.

The deposit has been explored and delineated with surface geological mapping and sampling, airborne and ground geophysical surveys (magnetics, EM, IP) and diamond drilling. Detailed mapping of stripped outcrops reveals complex hydrothermal alteration assemblages (e.g., amphibole, biotite, muscovite, silica-sodic and epidote) and associated gold mineralization.

Lithology Map
‍Skidder outcrop is approximately 113 m long with an average width of 18 m. The outcrop is predominantly composed of medium-grained tonalite. The tonalite contains abundant, variably sized (~10 cm to <12 m) clasts of diorite and quartz diorite and is cut by lamprophyre dyke.

Silica-Albite alteration map
‍Alteration of the Skidder outcrop consists of silica-albite and sericite alteration. The dominant alteration is silica-albite, which occurs as fracture-controlled and pervasive alteration. Weak silica-albite alteration occurs in the northern part of the outcrop, becoming more intense towards the centre of the outcrop.

Outcrop aerial photo

Mineralization

The Côté Gold deposit gold mineralization is centred on breccia bodies of magmatic and hydrothermal origin within host tonalitic and dioritic intrusive rocks. Associated mineralization occurs in veins (sheeted veins and stockworks) and as disseminations. Disseminated mineralization in the hydrothermal matrix of the breccia is the most important style of the gold–copper mineralization and consists of disseminated pyrite, chalcopyrite, pyrrhotite, magnetite, gold (often in native form), and locally molybdenite in the breccia matrix.

Hydrothermal breccia

Diorite breccia

Disseminated sulphide mineralization in the hydrothermal matrix

Additional Mineralization Styles Identified Within the Deposit Include:

Quartz vein and fracture-associated visible gold

Orogenic or structurally-hosted vein occurrences

Syenite intrusion-related gold zones

Exploration and Resource Information

IAMGOLD is exploring in the Gosselin Zone, adjacent to Côté. For more information on exploration and the Côté Gold resource, visit the IAMGOLD website.

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