Abstract:

The Noranda mining district is one of Canada's nation builders, having been the key for opening up northern Quebec for economic expansion and regional development. Over an 85-year period, 20 economic volcanogenic massive sulphide (VMS) deposits have been discovered by prospecting, geological, geophysical and lithogeochemical techniques. Besides VMS deposits, the Noranda District is also host to 19 orogenic Au deposits and several intrusion-hosted Cu-Mo deposits and occurrences. VMS deposits of the Noranda District occur in the Noranda formation of the Archean Blake River Group of the Abitibi Subprovince. The majority of deposits are hosted within the Noranda Cauldron, an asymmetric volcanic depression filled with effusive basalt and basaltic andesite flows and subordinate rhyolite flowdome complexes. The Noranda Cauldron is floored by a large, multiphase subvolcanic intrusive complex that is hypothesized to be the heat engine responsible for development of much of the VMS and porphyry mineralization in the district. The VMS deposits are hosted by two distinct lithofacies, flow and volcaniclastic, where volcaniclastic includes primary pyroclastic deposits, and those that are re-deposited and syneruptive. Of the 20 past producing VMS deposits, 17 are hosted by flows (8 with mafic and 9 with felsic flows) whereas volcaniclastic rocks host the Horne, Bouchard-Hebert and Corbet deposits. The largest massive sulphide deposits occur within the felsic volcaniclastic strata at the margins of or directly overlying the Noranda Cauldron. <br/><br/>The Noranda VMS deposits typify the bimodal-mafic type, where the majority of the host stratigraphy is composed of a mafic volcanic flow succession in which discrete felsic dome complexes are situated over major synvolcanic faults. These fault systems are also defined within the Noranda Cauldron by discrete dyke swarms originating from the underlying subvolcanic intrusive complex. The inferred primitive rifted arc environment typical of this deposit-type is best characterized by a large volcanic edifice within the present-day Kermadec and Tonga-Fiji suprasubduction tectonic zone of the western Pacific.