Summary:
Deposit Type
The Doyon-Bousquet-LaRonde(DBL) mining camp is one of Canada’s largest VMS districts (Mercier-Langevin, Dubé and Blanchet, et al. 2017). The mineralization on the Property has been well documented by various researchers and is recognized as comprised of world-class, gold-rich VMS deposits formed in a submarine back-arc basin or submarine arc crust. Like other VMS-type deposits, the LaRonde Complex’s lenses were formed mainly by sulphide precipitation from hydrothermal fluids on an Archean seafloor and by sulphide replacement in the footwall below the lenses.
Two deposits styles are recognized on the Property:
• Gold-rich base metal massive sulphide lenses (LaRonde Penna, Bousquet No. 2-Dumagami), which represent the exhalative part of a VMS-type system above the seafloor.
• Gold-rich vein stockworks and sulphide disseminations (Bousquet No. 1-LZ5 and Ellison); which represent the sub-seafloor stockwork and replacement-style VMS-type system (feeder zone) into permeable (i.e., fragmental) facies in volcanic rocks such as breccia, volcanic tuff, pyroclastic unit, etc.
Mineralization
Mineralization at the LaRonde Complex is hosted within the Archean volcanic and intrusive rocks of the Bousquet Formation (2,699 to 2,696 Ma) which is one of the youngest assemblages of the Blake River Group (2,703 to 2,694 Ma). Approximately 50 km to the west, the Blake River Group also hosts several world-class deposits in the Rouyn-Noranda mining camp including the Horne and Quémont deposits.
The synvolcanic mineralization occurs as two main styles: gold-rich polymetallic massive sulphide lenses (LaRonde Penna and Bousquet 2-Dumagami); and gold-rich sulphide veins, breccia, stockworks and dissemination ore zones (Bousquet 1 – LZ5). Sulphide veins and stockworks can be hosted in mafic to felsic host rocks. Both mineralization styles occur as single lenticular bodies.
The LaRonde Complex mineralization consists of an assemblage of disseminated to massive sulphide lenses that are stacked within the Upper Member of the Bousquet Formation. These lenses are typically polymetallic with a pyrite ± sphalerite-chalcopyrite-galena-pyrrhotite-gold assemblage. The lenses are stratiform, showing the same east-west dipping south attitude as the host rocks. The principal deformation affecting ore lenses is the strong regional north-south flattening (D2) with a south-southwest plunging stretching, giving an elongated tabular form to all lenses. All lenses show a similar subvertical dip of 80° (±10°) to the south. The widths of the lenses vary from less than 1 m up to 40 m, while their continuous lengths vary from less than 100 m up to 3 km in the case of the unique Zone 20 North.
The structural deformation of orebodies has locally affected the mineralization. Shears, fractures and quartz veins show evidence of gold remobilization along with tellurides, chalcopyrite and other sulphide assemblages.
In the vicinity of the Penna Shaft, four mineralized horizons are known and they host lenses that range in size from 20,000 tonnes to more than 60 million tonnes.
The LaRonde Zone 5 horizon consists of a four-to-30 metres thick horizon of disseminated to stringer sulphide mineralization containing 5% to 20% pyrite and traces of chalcopyrite with rare millimetre-wide grains of visible gold. The LaRonde Zone 5 horizon has a large geological footprint and has been estimated to contain a mass of more than 26 million tonnes. The LaRonde Zone 5 horizon can be followed over 900 metres of east-west strike length over the Bousquet property and another 400 metres on the Ellison property for a total strike length of 1,300 metres. LaRonde Zone 5 has been traced vertically for almost 1,000 metres showing a steep dip to the southwest. In an enlarged area of LaRonde Zone 5, there is gold enrichment near the margins of the economic envelope. LaRonde Zone 5 includes two high grade portions named Zone 5 Footwall and Zone 5 hanging wall.