The Archaean Westwood Au deposit, southern Abitibi: telescoped Au-rich VMS and intrusion-related Au systems.

The Westwood deposit (3.74 Moz Au) is part of the Doyon-Bousquet-LaRonde mining camp. The deposit is hosted in the 2 699-2 996 Ma Bousquet Formation. The Westwood deposit consists of three east-west-trending and steeply south-dipping mineralised corridors stacked from north to south: the Zone 2 Extension, the North Corridor, and the Westwood Corridor. The Zone 2 Extension consists of transposed cm- to dm-wide pyrite ± chalcopyrite-sphalerite-rich quartz veins and disseminations whereas the North Corridor consists of cm- to dm-wide quartz-pyrite-chalcopyrite ± sphalerite-galena-pyrrhotite veins and disseminations as well as thin, semi-massive to massive sulphide veins. The Westwood Corridor consists of discontinuous stratabound polymetallic semi-massive to massive sulphide lenses, veins and disseminations. Mapping and 3-D modelling of the alteration zones strongly suggests that the Zone 2 Extension alteration overprints that of the North and Westwood corridors. By analogy with telescoped porphyry-epithermal systems, the three mineralised corridors may represent various components of a submarine Archaean auriferous synvolcanic magmatic-hydrothermal system, providing a unique opportunity to improve and expand metallogenic and exploration models for Archaean greenstone belts.
The Westwood deposit (3.74 Moz Au) is part of the Doyon-Bousquet-LaRonde mining camp. The deposit is hosted in the 2 699-2 996 Ma Bousquet Formation. The Westwood deposit consists of three east-west-trending and steeply south-dipping mineralised corridors stacked from north to south: the Zone 2 Extension, the North Corridor, and the Westwood Corridor. The Zone 2 Extension consists of transposed cm- to dm-wide pyrite ± chalcopyrite-sphalerite-rich quartz veins and disseminations whereas the North Corridor consists of cm- to dm-wide quartz-pyrite-chalcopyrite ± sphalerite-galena-pyrrhotite veins and disseminations as well as thin, semi-massive to massive sulphide veins. The Westwood Corridor consists of discontinuous stratabound polymetallic semi-massive to massive sulphide lenses, veins and disseminations. Mapping and 3-D modelling of the alteration zones strongly suggests that the Zone 2 Extension alteration overprints that of the North and Westwood corridors. By analogy with telescoped porphyry-epithermal systems, the three mineralised corridors may represent various components of a submarine Archaean auriferous synvolcanic magmatic-hydrothermal system, providing a unique opportunity to improve and expand metallogenic and exploration models for Archaean greenstone belts.