Stratigraphic and structural setting of gold and nickel deposits in the La Motte–Malartic area, southern Abitibi and Pontiac subprovinces, Superior Province, Quebec

The Superior Province is the largest exposed Archean craton in the world. It consists of generally east-striking subprovinces (e.g., Abitibi, Uchi) consisting of metavolcanic and granitoid rocks separated by subprovinces (e.g., Pontiac, English River) dominated by metasedimentary and gneissic rocks (Robert et al., 2005). Numerous world-class gold, volcanogenic massive sulphide and less-common magmatic nickel-copper deposits are spatially associated with east-striking subvertical crustal-scale fault zones along the subprovince boundaries (e.g., Cadillac–Larder Lake fault zone), or along the contact zones (Porcupine–Destor–Manneville fault zone) between metavolcanic and metasedimentary rocks within subprovinces (Robert and Poulsen, 1997; Hannington et al, 1999). These province-scale faults exert key controls on the formation of deposits since they act as conduits for the flow and migration of ore-forming fluids. In addition, post-mineralization deformation can subsequently modify geometry and metal grade of ore deposits.

In order to reveal the fundamental geological processes that were responsible for the formation of mineral deposits in southern Superior Province, the Mineral Exploration Research Centre at the Harquail School of Earth Sciences launched four mapping projects in the area of seismic-magnetotelluric transects in Malartic, Rouyn-Noranda, Larder Lake and Swayze in the summer of 2017. This contribution highlights preliminary results from the first field season in the LaMotte–Malartic area along the central and southern Malartic transect (Figure 1). In this article, the stratigraphic and structural setting of veintype and disseminated gold deposits hosted in metasedimentary and metavolcanic rocks (Pontiac, Cadillac, Timiskaming and Piché groups) at or near the Cadillac–Larder Lake fault zone are examined, as well as little-known nickel-copper mineralization in metavolcano-sedimentary rocks (Malartic group) at the Southern Manneville fault zone.

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