The Porcupine mine consists of the Hoyle Pond and Dome underground and a central milling facility within the city of Timmins, Ontario. The mine have produced more than 64 million ounces of gold since production began in 1910 and include North America's longest continually operating gold mine. The operating properties, combined with extensive and highly prospective land holdings, are strategically located in one of the world's great gold producing camps.
In 2009, gold production amounted to 318 kounces. The Porcupine mine has an expected mine life through 2016.
The Porcupine mines are a group of open pit and underground gold mines located in Timmins, Ontario, Canada.
The Porcupine mines are situated in the Porcupine Camp in Archean rocks of the western Abitibi Greenstone belt of the Superior Province in the Canadian Shield. These consist of ultramafic and mafic volcanic rocks of the Keewatin subgroup overlain by sedimentary rocks of the Timiskaming group. The lands lie adjacent and to the north of the regionally significant Porcupine Destor Fault.
The Dome mine lies on the south limb of the Porcupine syncline where the Tisdale group volcanic rocks are overlain unconformably by the Timiskaming metasedimentary slates and conglomerates. Porphyry bodies, namely the Preston Porphyry are seen in the mine and can host gold mineralization, in addition to the volcanic and sedimentary rocks. Gold mineralization is found in a number of different structural settings and mineralization consists of continuous quartz carbonate veins, quartz tourmaline veins, quartz stockworks and gold associated with disseminated sulphides.
Hoyle Pond is situated in a similar environment but the mineralization is predominantly hosted in two packages of mafic volcanic rocks flanking an ultramafic core with small units of porphyritic rocks. Mineralization is mainly high-grade, and found in narrow quartz veins, which are generally sub- vertical but can be flat as in the case of the 7 vein structures. Gold is most frequently in the native state or with pyrite, but can sometimes be found associated with arsenopyrite.
Pamour is located along the Keewatin-Timiskaming unconformity where older Keewatin mafic and ultramafic volcanic rocks overlie younger Timiskaming sedimentary rocks. Mineralization occurs as higher-grade narrow quartz veins in the volcanic and sedimentary rocks, and as lower-grade extension vein sets in and around a Timiskaming conglomerate unit.
Mining & Operation
Underground mining is conducted at the Hoyle Pond site at a planned rate of 1,178 tonnes per day. Hoyle Pond underground mine is accessed both by decline and by a shaft, which accesses the bottom track haulage level at 720 metres.
The current ramp is now advancing to depths greater than 1,100 metres below surface and is interconnected with a recently commissioned internal winze at a depth of approximately 920 metres. The current winze configuration has potential for expansion to a depth beyond 1,300 metres below surface. Mining methods employed are conventional cut and fill, shrinkage, panel mining, and longhole methods in wider zones.
The Dome open pit completed mining in 2005. Extensive stockpiles were accumulated during mining and these will be used to supplement ore from the active Pamour open pit in 2006 The Pamour open pit ramped up to full production during 2005 and will be mined in three stages utilizing the existing Dome open pit equipment, mining methods and procedures. Mining is conducted using conventional open pit mining methods utilizing diesel powered drills, electric cable shovels, 136 tonne haulage trucks, front-end loaders, dozers and other support equipment. All mining is carried out on 9 metre benches. Pit wall inter-ramp angles vary; haulage ramp gradients are set to 10%. Pamour ore is transported to the Dome mill via a 12 kilometre dedicated haul road utilizing 136 tonne haulage trucks.
The Dome underground operation was restarted in 2006 after being placed on care and maintenance in 2004 due to depletion of resources at then current gold prices.
Gold is recovered using a combination of gravity concentration and cyanidation techniques. The circuit consists of primary, secondary and tertiary crushing, rod/ball mill grinding, gravity concentration, cyanide leaching, carbon-in-pulp gold recovery, stripping, electro winning and refining.
Hoyle Pond ore is crushed in the Dome open pit primary crushing plant along with open pit ore and Dome underground ore before being fed to a two-stage secondary crushing plant located north of the ultimate pit. Tailings are impounded in the No. 6 tailing area southeast of the mine site.