Abstract
The Chevrier gold deposit is located in the northeastern part of the Abitibi Subprovince within the Chevrier volcanic centre (CVC). This calc-alkaline volcanic centre evolved from mafic to felsic in a submarine environment, and the Chevrier deposit is spatially associated with the uppermost unit composed mostly of massive dacite to rhyolite, dated at 2730 Ma. The Chevrier deposit is divided in two zones. The North Zone is composed of high-grade, discordant quartz-carbonate veins and disseminated pyrite mostly within melanocratic gabbro dykes, whereas, the South Zone is within a low-grade, concordant pyrite envelope associated with quartz-carbonate-pyrite veinlets. Both zones are highly deformed and show strong carbonate, sericite and chlorite alterations. Although these zones share many characteristics with orogenic deposits, the crosscutting of the Chevrier deposit by structures associated with the major deformation events suggests that mineralization was prior to these events. Furthermore, felsic dykes associated with the formation of the CVC crosscut auriferous veins and zones, therefore suggesting a synvolcanic timing for the gold mineralization. Characteristics of the zones, such as similar vein composition and alteration mineral assemblages and location within the volcanic pile, suggest that they are part of a single hydrothermal event where the South Zone represents the shallower part of the deposit. The Chevrier deposit is classified as a noncarbonate-hosted stockwork and disseminated deposit and shows many similarities with strata-bound gold deposits of the Andacollo mining district of Chile. Dating of mineralization at the Chevrier deposit indicates that the emplacement of gold occurred more than 25 Ma before the onset of the orogeny affecting this part of the Abitibi subprovince. It also illustrates how synvolcanic mineralization can be misinterpreted as an orogenic deposit without the presence of crosscutting relationships with dykes, faults or other structures.
Published Version
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