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TitleGeology of the Horne massive sulphide deposit, Rouyn-Noranda, Quebec, Symposium on Precambrian metallogeny
AuthorMonecke, T; Gibson, H; McNicoll, V; Dubé, B
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 34, 2011 p. 144
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20130573
File formatpdf
NTS32D/02; 32D/03; 32D/06; 32D/07
Lat/Long WENS-79.2500 -78.7500 48.3333 48.1667
Subjectseconomic geology; stratigraphy; igneous rocks; volcanic rocks; plutonic rocks; facies; mineral occurrences; volcanogenic deposits; mineral deposits; gold; copper; mineralization; sulphides; sulphide deposits; volcaniclastics; breccia deposits; breccias; breccias, volcanic; tuffs; Archean; rhyolites; dykes; diabase dykes; bedrock geology; Horne Deposit; Noranda Volcanic Complex; Precambrian; Proterozoic
ProgramTargeted Geoscience Initiative (TGI-4), Gold Ore Systems
AbstractThe Horne deposit in the Noranda mining district, northwestern Quebec, represents one of the largest volcanic-hosted massive sulfide deposits in the world. Between 1927 and 1976, the mine produced 260 t of Au and 1.13 Mt of Cu making it one of the largest gold producers of its class. Over the past years, an extensive research program has been carried out to better define the volcanological and stratigraphic setting of the deposit. Detailed surface mapping has shown that the host rock succession of the Horne deposit is dominated by a proximal facies association comprising coherent rhyolite and associated volcaniclastic rocks that formed by autobrecciation and quench fragmentation. Effusive and shallow intrusive volcanism occurred broadly contemporaneously with the deposition of mass-flow derived volcanic debris containing pyroclasts generated by felsic explosive eruptions. Deposition of volcaniclastic lithofacies occurred, at least in part, in topographic depressions that are bounded by synvolcanic faults. Synvolcanic faults are commonly marked by abrupt changes in volcanic facies and the presence of felsic and mafic dikes or apophyses of synvolcanic intrusions. The synvolcanic faults also appear to control the location of sulfide mineralization and associated hydrothermal alteration. Field relationships indicate that massive sulfide formation broadly coincided with a shift from felsic to mafic volcanism as the felsic-dominated host succession is crosscut by a mafic dike swarm that extends towards a succession of less intensely altered mafic rocks in the hanging wall to the deposit. Massive sulfide formation occurred over a prolonged period of time resulting in the formation of a stratigraphically stacked, hydrothermal ore system. Widespread sulfide infiltration and replacement of permeable volcaniclastic strata and associated hydrothermal alteration suggest that processes of subseafloor replacement were important in contributing to the unusual size of the Horne deposit. However, incorporation of massive sulfide clasts into mass-flow derived volcaniclastic deposits suggests that massive sulfides were at least locally exposed at the ancient seafloor. TIMS U/Pb dating of a rhyolite sill showed that the Horne succession formed at 2702.2±0.9 Ma. This is comparable to the emplacement age of a coherent rhyolite occurring in the footwall of the Quemont massive sulfide deposit, located immediately to the north of the Horne Creek fault. Based on these age constraints and lithological similarities between the host rock successions, it appears likely that the gold-rich Horne and Quemont deposits formed broadly contemporaneously during an early period of felsic- dominated submarine volcanism of the Blake River Group.