GEOLOGY AND STRUCTURE OF A SULFIDE-RICH GOLD DEPOSIT - AN EXAMPLE FROM THE MOUSKA GOLD MINE, BOUSQUET DISTRICT, CANADA

The Mouska mine in the Bousquet mining district represents a sulfide-r ich gold deposit hosted by the Archean mafic metavolcanites of the Bla ke River Group, southern Abitibi greenstone belt. Mineralization shows both lithological and structural control and coincides with variably oriented high angle-reverse ductile and brittle-ductile shear zones. H ost shear zones are superimposed on the regional foliation, and both a ppear to have formed from the same bulk stress field. Gold mineralizat ion is composed of sulfide and quartz lodes and is associated with thr ee district ore zones; each differs from the others by its style of ve ining and the nature of tectono-metamorphic overprint. Sulfide mineral ization in this area varies from semimassive to massive sulfide lodes and dissemination. The strain features and age relationships of ore-be aring rocks and vein material throughout the ore zones display evidenc e of earlier sulfide mineralization with gold. This mineralization is pretectonic (with respect to the development of the foliation) and is interpreted as hydrothernlal-synvolcanic. The auriferous quartz sulfid e veins correspond to a multistage syn- to late tectonic mineralizatio n and clearly crosscuts massive sulfide bodies. In the Mouska deposit, strain features and structural setting of gold mineralization show in teractions between lithological factors, such as contacts, competence contrast and rock-body geometry, and die presence of pretectonic sulfi des. In several parts of the mine volcanic sequence, the shear zone nu cleation and development were controlled by both rock heterogeneities and the presence of soft sulfide bodies. The sulfides, in particular, were responsible for the structural instability recorded in some volca nic contacts and their activation as shear zones. In other parts, the sulfides have variably influenced the local slip movement. The shapes of ore shoots throughout the ore zones are variable and interpreted as reflecting the initial geometry of anisotropic interfaces involved in the deformation history.