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.
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.
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.