Name: Brucejack mine.
Location: The Brucejack mine project is located about 65 km north of Stewart, in north-western British Columbia, Canada.
Controlling Company: Pretium Resources (Pretivm).
Brief History: The Brucejack property and surrounding region have a history rich in exploration for precious and base metals dating back to the late 1800s. In 2009, Silver Standard began work on the property. The 2009 programme included drilling, rock-chip and channel sampling, and resampling of historical drill core. In 2010, pursuant to a purchase and sale agreement between Silver Standard (as the seller) and Pretivm (as the buyer), Silver Standard sold to Pretivm all of the issued shares of 0890693 BC – the owner of the project – and the adjacent Snowfield project.
Brief Description: Brucejack is part of a largely unexplored land package of more than 103 000 ha. The focus of the project is the Valley of the Kings (VOK), which comprises high-grade visible gold stringers within a lower-grade gold quartz stockwork system. The mine is expected to produce 7.27-million ounces of gold over an 18-year mine life, and commercial production is scheduled for 2017.
Geology/Mineralisation: The Brucejack deposit is considered to be a transitional to intermediate sulphidation epithermal stockwork vein system-hosted gold/silver deposit that was developed in a dynamic extensional basin. It is likely associated with a deeper porphyry system that developed within an active island arc tectonic setting.
The property is largely underlain by volcano-sedimentary rocks of the Lower Jurassic Hazelton group. These rocks unconformably overlie volcanic arc sedimentary rocks of the Upper Triassic Stuhini group along the westernmost part of the property.
Gold/silver mineralisation is hosted in predominantly subvertical vein, vein stockwork, and subordinate vein breccia systems of variable intensity. The vein/stockwork systems display parallel and discordant relationships to stratigraphy. These systems are relatively continuous along strike, from tens of metres to several hundreds of metres.
Several mineralisation zones have been explored to varying degrees, including (from south to north): the Bridge zone, the VOK zone, the West zone, Gossan Hill, the Shore zone, and the SG zone.
High-grade gold mineralisation in the VOK, the current focus of the project, occurs in a series of west-north-west and subordinate west-southwest-trending subvertical corridors of structurally reorientated vein stockworks and vein breccias. Stockwork mineralisation displays discordant and concordant relationships to the volcanic pile stratigraphy. Gold is typically present as gold-rich electrum within deformed quartz-carbonate vein stockworks, veins and subordinate vein breccias.
Recent underground exploration conducted as part of the bulk sample programme confirmed the location of corridors of stockwork-style mineralisation and the lithological contacts in this part of the deposit within the VOK.
The VOK deposit is currently defined over 1 200 m in east-west extent, 600 m in north-south extent and up to 650 m in depth below the topographic surface. The West zone appears to form the northern limb of an anticline that links up with the VOK in the south, and the southern limb of a syncline that extends further to the north. This zone, which is currently defined over 590 m along its north-west strike, 560 m across strike and down to 650 m in depth, is open to the north-west, south-east and at depth to the north-east.
Reserves: Total proven and probable reserves as at June 2014 were estimated at 16.5-million tonnes grading 14.1 g/t of gold and 57.7 g/t of silver.
Products: Gold and silver.
Mining Method: Long-hole stoping and cemented paste backfill.
Major Infrastructure and Equipment: The process flowsheet developed for the Brucejack mineralisation is a combination of conventional bulk sulphide flotation and gravity concentration to recover gold and silver.
The process plant will produce a gold-silver-bearing flotation concentrate and gold/silver doré by melting the gravity concentrate produced from the gravity concentration circuits. It will comprise primary crushing underground; a conveying system for crushed ore; primary grinding gravity concentration; rougher/scavenger flotation; bulk flotation concentrate regrinding and gravity concentration; cleaner flotation; gravity concentrate smelting to produce dore; flotation concentrate dewatering, bagging and load out; and tailings disposal to the tailings impoundment or to the underground mine for backfilling.
Prospects: Pretivm has contracted AMEC Americas to provide the engineering, procurement and construction management services for the Brucejack mine project.
Contact Person: VP, corporate relations Michelle Romero.
Contact Details:
Pretivm Resources,
tel +1 604 558 1784,
email invest@pretivm.com,
website http://www.pretivm.com.