Item

Abstract

The Great Bear magmatic zone (GBnnz) contains several examples of iron oxide copper-gold (IOCG) mineralization including the Sue-Dianne and NICO deposits and other prospects like DAMP. The delta S-34 values in pyrite, arsenopyrite and chalcopyrite from NICO range from 2.5 parts per thousand to 6.7 parts per thousand; pyrite from DAMP varies from - 0.1 parts per thousand to 5 parts per thousand. Conversely, chalcopyrite from Sue Dianne delta S-34 has a dominantly negative signature ranging from - 7.7 parts per thousand to 1 parts per thousand. The preliminary delta S-34 data have values close to 0 parts per thousand suggesting an important magmatic contribution to the formation of IOCGs in the GBmz. However, some of the relatively S-34-enriched (> 5 parts per thousand) and -depleted (<-5 parts per thousand) signatures could also indicate that some of the sulphur found in these systems is derived from non-magmatic sources. In addition, Re-187-Os-187 dating of two molybdenite samples was carried out on NICO deposit. One sample represents a late stage of mineralization (NM3) within the main ore zone and has an age of ca.1865. The second sample formed ca.1877 and was collected from a U +/- Cu-Mo- rich zone within the Southern Breccia. The Re-187-Os-187 molybenite ages from NICO deposit also suggest a magmatic origin as they are correlative (within error) with plutonic events emplaced between 1866 Ma and 1875 Ma in this area.